[Intel-xe] [PATCH 23/23] drm/xe: Introduce a new DRM driver for Intel GPUs
Rodrigo Vivi
rodrigo.vivi at intel.com
Fri Feb 17 17:54:24 UTC 2023
On Mon, Jan 30, 2023 at 05:37:22PM -0800, Matt Roper wrote:
> On Tue, Jan 10, 2023 at 05:54:49PM -0500, Rodrigo Vivi wrote:
> > From: Matthew Brost <matthew.brost at intel.com>
> >
> > Xe, is a new driver for Intel GPUs that supports both integrated and
> > discrete platforms starting with Tiger Lake (first Intel Xe Architecture).
> >
> > The code is at a stage where it is already functional and has experimental
> > support for multiple platforms starting from Tiger Lake, with initial
> > support implemented in Mesa (for Iris and Anv, our OpenGL and Vulkan
> > drivers), as well as in NEO (for OpenCL and Level0).
> >
> > The new Xe driver leverages a lot from i915.
> >
> > As for display, the intent is to share the display code with the i915
> > driver so that there is maximum reuse there.
> >
> > This initial work is a collaboration of many people and unfortunately
> > the big squashed patch won't fully honor the proper credits. But let's
>
> I'm not sure how you want to handle general review for the big mass of
> pre-existing code. I haven't looked through all of the giant squashed
> patch, but I've included some comments/questions inline below for things
> that popped out to me while browsing through this. Not saying that you
> or anyone specific needs to address this immediately or anything; these
> are just things I wanted to jot down and mention before I forget about
> them.
Thank you so much for sending this feedback here. I totally agree
that the big squash is horrible for reviewing.
I will try to answer a few questions below and open gitlab-issues
for other cases.
>
> ...
> > diff --git a/drivers/gpu/drm/xe/xe_bo.c b/drivers/gpu/drm/xe/xe_bo.c
> ...
> > +int xe_gem_create_ioctl(struct drm_device *dev, void *data,
> > + struct drm_file *file)
> > +{
> ...
> > +
> > + if (args->flags & XE_GEM_CREATE_FLAG_SCANOUT)
> > + bo_flags |= XE_BO_SCANOUT_BIT;
>
> So if an object is eligible to be flipped to a display plane, it should
> be allocated that way up front? How does that work when the client
> allocating the buffer is separate from the display server responsible
> for presentation? If the 3D or media client allocating the buffer
> doesn't know what the compositor is going to do with it (i.e., flip to a
> plane vs compose with 3D), they should probably just set the scanout bit
> on every buffer just to be safe?
>
> With the display code living in i915, I guess there's nothing trying to
> enforce that we don't try to flip a buffer that wasn't flagged as
> scanout, so if userspace does the wrong thing it's just their own fault.
https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/213
>
> ...
> > +
> > +int xe_bo_lock(struct xe_bo *bo, struct ww_acquire_ctx *ww,
> > + int num_resv, bool intr)
>
> You might want some kerneldoc on this one. I.e., what exactly does
> locking/unlocking a bo do/protect?
Yes, we need to have a better documentation anyway.
The goal of this lock is to protect the data on cases like eviction.
In the back it using the tmm reservation with ww mutex.
https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/214
>
> ...
> > diff --git a/drivers/gpu/drm/xe/xe_bo.h b/drivers/gpu/drm/xe/xe_bo.h
> > new file mode 100644
> > index 000000000000..1a49c0a3c4c6
> > --- /dev/null
> > +++ b/drivers/gpu/drm/xe/xe_bo.h
> > @@ -0,0 +1,290 @@
> > +/* SPDX-License-Identifier: MIT */
> > +/*
> > + * Copyright © 2021 Intel Corporation
> > + */
> > +
> > +#ifndef _XE_BO_H_
> > +#define _XE_BO_H_
> > +
> > +#include "xe_bo_types.h"
> > +#include "xe_macros.h"
> > +#include "xe_vm_types.h"
> > +
> > +#define XE_DEFAULT_GTT_SIZE_MB 3072ULL /* 3GB by default */
> > +
> > +#define XE_BO_CREATE_USER_BIT BIT(1)
> > +#define XE_BO_CREATE_SYSTEM_BIT BIT(2)
> > +#define XE_BO_CREATE_VRAM0_BIT BIT(3)
> > +#define XE_BO_CREATE_VRAM1_BIT BIT(4)
> > +#define XE_BO_CREATE_VRAM_IF_DGFX(gt) \
> > + (IS_DGFX(gt_to_xe(gt)) ? XE_BO_CREATE_VRAM0_BIT << gt->info.vram_id : \
> > + XE_BO_CREATE_SYSTEM_BIT)
> > +#define XE_BO_CREATE_GGTT_BIT BIT(5)
> > +#define XE_BO_CREATE_IGNORE_MIN_PAGE_SIZE_BIT BIT(6)
> > +#define XE_BO_CREATE_PINNED_BIT BIT(7)
> > +#define XE_BO_DEFER_BACKING BIT(8)
> > +#define XE_BO_SCANOUT_BIT BIT(9)
> > +/* this one is trigger internally only */
> > +#define XE_BO_INTERNAL_TEST BIT(30)
> > +#define XE_BO_INTERNAL_64K BIT(31)
> > +
> > +#define PPAT_UNCACHED GENMASK_ULL(4, 3)
> > +#define PPAT_CACHED_PDE 0
> > +#define PPAT_CACHED BIT_ULL(7)
> > +#define PPAT_DISPLAY_ELLC BIT_ULL(4)
> > +
> > +#define GEN8_PTE_SHIFT 12
> > +#define GEN8_PAGE_SIZE (1 << GEN8_PTE_SHIFT)
> > +#define GEN8_PTE_MASK (GEN8_PAGE_SIZE - 1)
> > +#define GEN8_PDE_SHIFT (GEN8_PTE_SHIFT - 3)
> > +#define GEN8_PDES (1 << GEN8_PDE_SHIFT)
> > +#define GEN8_PDE_MASK (GEN8_PDES - 1)
> > +
> > +#define GEN8_64K_PTE_SHIFT 16
> > +#define GEN8_64K_PAGE_SIZE (1 << GEN8_64K_PTE_SHIFT)
> > +#define GEN8_64K_PTE_MASK (GEN8_64K_PAGE_SIZE - 1)
> > +#define GEN8_64K_PDE_MASK (GEN8_PDE_MASK >> 4)
> > +
> > +#define GEN8_PDE_PS_2M BIT_ULL(7)
> > +#define GEN8_PDPE_PS_1G BIT_ULL(7)
> > +#define GEN8_PDE_IPS_64K BIT_ULL(11)
> > +
> > +#define GEN12_GGTT_PTE_LM BIT_ULL(1)
> > +#define GEN12_USM_PPGTT_PTE_AE BIT_ULL(10)
> > +#define GEN12_PPGTT_PTE_LM BIT_ULL(11)
> > +#define GEN12_PDE_64K BIT_ULL(6)
> > +#define GEN12_PTE_PS64 BIT_ULL(8)
> > +
> > +#define GEN8_PAGE_PRESENT BIT_ULL(0)
> > +#define GEN8_PAGE_RW BIT_ULL(1)
>
> We should try to avoid using deprecated "GEN" terminology in the Xe
> driver. And if we're only supporting Xe-based platforms and beyond,
> distinctions like "gen8" and "gen12" are pretty meaningless.
>
> Also, should some of the masks+shifts above be replaced with GENMASK and
> such so that it's easier to follow and less error-prone?
+1
https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/215
>
> ...
> > diff --git a/drivers/gpu/drm/xe/xe_debugfs.c b/drivers/gpu/drm/xe/xe_debugfs.c
> ...
> > +static int forcewake_open(struct inode *inode, struct file *file)
> > +{
> > + struct xe_device *xe = inode->i_private;
> > + struct xe_gt *gt;
> > + u8 id;
> > +
> > + for_each_gt(gt, xe, id)
> > + XE_WARN_ON(xe_force_wake_get(gt_to_fw(gt), XE_FORCEWAKE_ALL));
> > +
> > + return 0;
> > +}
> > +
> > +static int forcewake_release(struct inode *inode, struct file *file)
> > +{
> > + struct xe_device *xe = inode->i_private;
> > + struct xe_gt *gt;
> > + u8 id;
> > +
> > + for_each_gt(gt, xe, id)
> > + XE_WARN_ON(xe_force_wake_put(gt_to_fw(gt), XE_FORCEWAKE_ALL));
> > +
> > + return 0;
> > +}
> > +
> > +static const struct file_operations forcewake_all_fops = {
>
> For debugging purposes, would it be more useful to have per-GT forcewake
> nodes instead of one global node that grabs all the GTs? Or is this
> mainly just intended for a tool like IGT's 'intel_reg' that wants to be
> lazy and not worry about where the register really lives?
yes, this is exactly the case. A lazy IGT case where we want to ensure
that we get the right read of registers without having to care about
the domain.
>
> > + .owner = THIS_MODULE,
> > + .open = forcewake_open,
> > + .release = forcewake_release,
> > +};
> > +
>
> ...
> > diff --git a/drivers/gpu/drm/xe/xe_device_types.h b/drivers/gpu/drm/xe/xe_device_types.h
> ...
> > +#define GRAPHICS_VER(xe) ((xe)->info.graphics_verx100 / 100)
> > +#define MEDIA_VER(xe) ((xe)->info.media_verx100 / 100)
> > +#define GRAPHICS_VERx100(xe) ((xe)->info.graphics_verx100)
> > +#define MEDIA_VERx100(xe) ((xe)->info.media_verx100)
>
> As a reminder, although we use version numbers like "12.50" in
> shorthand, they're not actually decimal numbers, but rather a
> concatenation of an "architecture" version and a "release" version. So
> x.1, x.10, and x.100 are all different, and there's nothing that says
> release numbers can't go above 100. For platforms with GMD_ID, they're
> encoded in an 8-bit field, so they can potentially go up to 255 (and
> we're already up to 71 with some variants of MTL). Using an encoding
> that breaks down as soon as things go over 100 might be a bit risky?
the risk does exist, but I believe it is very very low and unlikely
at this moment. Can we worry about that when we have a real case?
>
> > +#define IS_DGFX(xe) ((xe)->info.is_dgfx)
> > +
> > +#define XE_VRAM_FLAGS_NEED64K BIT(0)
> > +
> > +#define XE_GT0 0
> > +#define XE_GT1 1
> > +#define XE_MAX_GT (XE_GT1 + 1)
> > +
> > +#define XE_MAX_ASID (BIT(20))
> > +
> > +#define IS_PLATFORM_STEP(_xe, _platform, min_step, max_step) \
> > + ((_xe)->info.platform == (_platform) && \
> > + (_xe)->info.step.graphics >= (min_step) && \
> > + (_xe)->info.step.graphics < (max_step))
> > +#define IS_SUBPLATFORM_STEP(_xe, _platform, sub, min_step, max_step) \
> > + ((_xe)->info.platform == (_platform) && \
> > + (_xe)->info.subplatform == (sub) && \
> > + (_xe)->info.step.graphics >= (min_step) && \
> > + (_xe)->info.step.graphics < (max_step))
> > +
> > +/**
> > + * struct xe_device - Top level struct of XE device
> > + */
> > +struct xe_device {
> > + /** @drm: drm device */
> > + struct drm_device drm;
> > +
> > + /** @info: device info */
> > + struct intel_device_info {
> > + /** @graphics_verx100: graphics IP version */
> > + u32 graphics_verx100;
> > + /** @media_verx100: media IP version */
> > + u32 media_verx100;
> > + /** @mem_region_mask: mask of valid memory regions */
> > + u32 mem_region_mask;
> > + /** @is_dgfx: is discrete device */
> > + bool is_dgfx;
> > + /** @platform: XE platform enum */
> > + enum xe_platform platform;
> > + /** @subplatform: XE subplatform enum */
> > + enum xe_subplatform subplatform;
> > + /** @devid: device ID */
> > + u16 devid;
> > + /** @revid: device revision */
> > + u8 revid;
> > + /** @step: stepping information for each IP */
> > + struct xe_step_info step;
> > + /** @dma_mask_size: DMA address bits */
> > + u8 dma_mask_size;
> > + /** @vram_flags: Vram flags */
> > + u8 vram_flags;
> > + /** @tile_count: Number of tiles */
> > + u8 tile_count;
> > + /** @vm_max_level: Max VM level */
> > + u8 vm_max_level;
> > + /** @media_ver: Media version */
> > + u8 media_ver;
>
> Do we need this if we have the full IP version up above?
indeed.
https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/216
>
> ...
> > + /** @gt: graphics tile */
> > + struct xe_gt gt[XE_MAX_GT];
>
> 'GT' is an old acronym that technically stands for 'graphics
> technology.' When the hardware people talk about a "tile" they're
> generally referring to the combination of "GT + lmem" as we have on PVC.
> Platforms like MTL that have multiple GTs are generally not considered
> multi-tile from the hardware point of view, although I know software
> people use the term inconsistently.
yes, 'tile' terminology is so confusing... we have so many 'tiles'
in so many different components/ip-blocks and they all mean different
things. Like a display centric dev looking at this 'graphics tile' would
think of the pixel positions and get really confused.
But when I think about the intel/xe_gt I believe it is easier to think in
tiles. Although I confess I get confused when someone ends up using 'tile'
term in MTL.
But should we just to a sed s/graphics tile/graphics technology/g ?
Well, but we need to consider that the plural of that would be entirely
missleading as well: 'graphics technologies'.
In MTL they are indeed 2 different technologies. In PVC they are the duplication
of the same technology.
What other better names do we have?
>
> ...
> > diff --git a/drivers/gpu/drm/xe/xe_force_wake.c b/drivers/gpu/drm/xe/xe_force_wake.c
> ...
> > +void xe_force_wake_init_gt(struct xe_gt *gt, struct xe_force_wake *fw)
> > +{
> > + struct xe_device *xe = gt_to_xe(gt);
> > +
> > + fw->gt = gt;
> > + mutex_init(&fw->lock);
> > +
> > + /* Assuming gen11+ so assert this assumption is correct */
> > + XE_BUG_ON(GRAPHICS_VER(gt_to_xe(gt)) < 11);
> > +
> > + if (xe->info.platform == XE_METEORLAKE) {
>
> This should be a version check rather than a platform check. We expect
> future platforms to also follow on with this new register.
+1.
https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/217
>
> > + domain_init(&fw->domains[XE_FW_DOMAIN_ID_GT],
> > + XE_FW_DOMAIN_ID_GT,
> > + FORCEWAKE_GT_GEN9.reg,
> > + FORCEWAKE_ACK_GT_MTL.reg,
> > + BIT(0), BIT(16));
>
> Since every call to domain_init() is using the same bit and mask
> parameters, we can just roll that into the implementation of
> domain_init().
not true... at least not anymore...
drivers/gpu/drm/xe/xe_force_wake.c: domain_init(&fw->domains[XE_FW_DOMAIN_ID_RENDER],
drivers/gpu/drm/xe/xe_force_wake.c- XE_FW_DOMAIN_ID_RENDER,
drivers/gpu/drm/xe/xe_force_wake.c- FORCEWAKE_RENDER_GEN9.reg,
drivers/gpu/drm/xe/xe_force_wake.c- FORCEWAKE_ACK_RENDER_GEN9.reg,
drivers/gpu/drm/xe/xe_force_wake.c- BIT(0), BIT(16));
drivers/gpu/drm/xe/xe_force_wake.c-
--
drivers/gpu/drm/xe/xe_force_wake.c: domain_init(&fw->domains[XE_FW_DOMAIN_ID_MEDIA_VDBOX0 + j],
drivers/gpu/drm/xe/xe_force_wake.c- XE_FW_DOMAIN_ID_MEDIA_VDBOX0 + j,
drivers/gpu/drm/xe/xe_force_wake.c- FORCEWAKE_MEDIA_VDBOX_GEN11(j).reg,
drivers/gpu/drm/xe/xe_force_wake.c- FORCEWAKE_ACK_MEDIA_VDBOX_GEN11(j).reg,
drivers/gpu/drm/xe/xe_force_wake.c- BIT(0), BIT(16));
drivers/gpu/drm/xe/xe_force_wake.c- }
--
drivers/gpu/drm/xe/xe_force_wake.c: domain_init(&fw->domains[XE_FW_DOMAIN_ID_MEDIA_VEBOX0 + j],
drivers/gpu/drm/xe/xe_force_wake.c- XE_FW_DOMAIN_ID_MEDIA_VEBOX0 + j,
drivers/gpu/drm/xe/xe_force_wake.c- FORCEWAKE_MEDIA_VEBOX_GEN11(j).reg,
drivers/gpu/drm/xe/xe_force_wake.c- FORCEWAKE_ACK_MEDIA_VEBOX_GEN11(j).reg,
drivers/gpu/drm/xe/xe_force_wake.c- BIT(0), BIT(16));
>
> > + } else {
> > + domain_init(&fw->domains[XE_FW_DOMAIN_ID_GT],
> > + XE_FW_DOMAIN_ID_GT,
> > + FORCEWAKE_GT_GEN9.reg,
> > + FORCEWAKE_ACK_GT_GEN9.reg,
> > + BIT(0), BIT(16));
> > + }
> > +}
> > +
> > +void xe_force_wake_init_engines(struct xe_gt *gt, struct xe_force_wake *fw)
> > +{
> > + int i, j;
> > +
> > + /* Assuming gen11+ so assert this assumption is correct */
> > + XE_BUG_ON(GRAPHICS_VER(gt_to_xe(gt)) < 11);
> > +
> > + if (!xe_gt_is_media_type(gt))
> > + domain_init(&fw->domains[XE_FW_DOMAIN_ID_RENDER],
> > + XE_FW_DOMAIN_ID_RENDER,
> > + FORCEWAKE_RENDER_GEN9.reg,
> > + FORCEWAKE_ACK_RENDER_GEN9.reg,
> > + BIT(0), BIT(16));
> > +
> > + for (i = XE_HW_ENGINE_VCS0, j = 0; i <= XE_HW_ENGINE_VCS7; ++i, ++j) {
> > + if (!(gt->info.engine_mask & BIT(i)))
> > + continue;
> > +
> > + domain_init(&fw->domains[XE_FW_DOMAIN_ID_MEDIA_VDBOX0 + j],
> > + XE_FW_DOMAIN_ID_MEDIA_VDBOX0 + j,
> > + FORCEWAKE_MEDIA_VDBOX_GEN11(j).reg,
> > + FORCEWAKE_ACK_MEDIA_VDBOX_GEN11(j).reg,
> > + BIT(0), BIT(16));
> > + }
> > +
> > + for (i = XE_HW_ENGINE_VECS0, j =0; i <= XE_HW_ENGINE_VECS3; ++i, ++j) {
> > + if (!(gt->info.engine_mask & BIT(i)))
> > + continue;
> > +
> > + domain_init(&fw->domains[XE_FW_DOMAIN_ID_MEDIA_VEBOX0 + j],
> > + XE_FW_DOMAIN_ID_MEDIA_VEBOX0 + j,
> > + FORCEWAKE_MEDIA_VEBOX_GEN11(j).reg,
> > + FORCEWAKE_ACK_MEDIA_VEBOX_GEN11(j).reg,
> > + BIT(0), BIT(16));
> > + }
> > +}
> > +
> > +void xe_force_wake_prune(struct xe_gt *gt, struct xe_force_wake *fw)
> > +{
> > + int i, j;
> > +
> > + /* Call after fuses have been read, prune domains that are fused off */
>
> It looks like both xe_force_wake_init_engines() and
> xe_force_wake_prune() are called from xe_gt_init() after
> the fuses are read in gt_fw_domain_init() has happened, we may not need
> the 'prune' function at all?
indeed. patch sent.
>
> > +
> > + for (i = XE_HW_ENGINE_VCS0, j = 0; i <= XE_HW_ENGINE_VCS7; ++i, ++j)
> > + if (!(gt->info.engine_mask & BIT(i)))
> > + fw->domains[XE_FW_DOMAIN_ID_MEDIA_VDBOX0 + j].reg_ctl = 0;
> > +
> > + for (i = XE_HW_ENGINE_VECS0, j =0; i <= XE_HW_ENGINE_VECS3; ++i, ++j)
> > + if (!(gt->info.engine_mask & BIT(i)))
> > + fw->domains[XE_FW_DOMAIN_ID_MEDIA_VEBOX0 + j].reg_ctl = 0;
> > +}
> > +
> > +static void domain_wake(struct xe_gt *gt, struct xe_force_wake_domain *domain)
> > +{
> > + xe_mmio_write32(gt, domain->reg_ctl, domain->mask | domain->val);
>
> I guess we can start with this, but as far as I know they've never fixed
> the case where sometimes forcewake requests get missed and require that
> we "kick" the punit by setting a second bit. We may need to bring back
> the more careful handling of forcewake if/when we start encountering
> sporadic failures.
should we read back and retry then? Since we don't have many cases and
it is only during initialization it shouldn't matter much. do you have
more info on the cases where that didn't 'kick' in?
>
> > +}
> > +
> > +static int domain_wake_wait(struct xe_gt *gt,
> > + struct xe_force_wake_domain *domain)
> > +{
> > + return xe_mmio_wait32(gt, domain->reg_ack, domain->val, domain->val,
> > + XE_FORCE_WAKE_ACK_TIMEOUT_MS);
> > +}
> > +
> > +static void domain_sleep(struct xe_gt *gt, struct xe_force_wake_domain *domain)
> > +{
> > + xe_mmio_write32(gt, domain->reg_ctl, domain->mask);
> > +}
> > +
> > +static int domain_sleep_wait(struct xe_gt *gt,
> > + struct xe_force_wake_domain *domain)
> > +{
> > + return xe_mmio_wait32(gt, domain->reg_ack, 0, domain->val,
> > + XE_FORCE_WAKE_ACK_TIMEOUT_MS);
> > +}
> > +
> > +#define for_each_fw_domain_masked(domain__, mask__, fw__, tmp__) \
> > + for (tmp__ = (mask__); tmp__ ;) \
> > + for_each_if((domain__ = ((fw__)->domains + \
> > + __mask_next_bit(tmp__))) && \
> > + domain__->reg_ctl)
> > +
> > +int xe_force_wake_get(struct xe_force_wake *fw,
> > + enum xe_force_wake_domains domains)
> > +{
> > + struct xe_device *xe = fw_to_xe(fw);
> > + struct xe_gt *gt = fw_to_gt(fw);
> > + struct xe_force_wake_domain *domain;
> > + enum xe_force_wake_domains tmp, woken = 0;
> > + int ret, ret2 = 0;
> > +
> > + mutex_lock(&fw->lock);
> > + for_each_fw_domain_masked(domain, domains, fw, tmp) {
> > + if (!domain->ref++) {
> > + woken |= BIT(domain->id);
> > + domain_wake(gt, domain);
> > + }
> > + }
> > + for_each_fw_domain_masked(domain, woken, fw, tmp) {
> > + ret = domain_wake_wait(gt, domain);
> > + ret2 |= ret;
> > + if (ret)
> > + drm_notice(&xe->drm, "Force wake domain (%d) failed to ack wake, ret=%d\n",
> > + domain->id, ret);
> > + }
> > + fw->awake_domains |= woken;
> > + mutex_unlock(&fw->lock);
> > +
> > + return ret2;
> > +}
> > +
> > +int xe_force_wake_put(struct xe_force_wake *fw,
> > + enum xe_force_wake_domains domains)
> > +{
> > + struct xe_device *xe = fw_to_xe(fw);
> > + struct xe_gt *gt = fw_to_gt(fw);
> > + struct xe_force_wake_domain *domain;
> > + enum xe_force_wake_domains tmp, sleep = 0;
> > + int ret, ret2 = 0;
> > +
> > + mutex_lock(&fw->lock);
> > + for_each_fw_domain_masked(domain, domains, fw, tmp) {
> > + if (!--domain->ref) {
> > + sleep |= BIT(domain->id);
> > + domain_sleep(gt, domain);
> > + }
> > + }
> > + for_each_fw_domain_masked(domain, sleep, fw, tmp) {
> > + ret = domain_sleep_wait(gt, domain);
> > + ret2 |= ret;
> > + if (ret)
> > + drm_notice(&xe->drm, "Force wake domain (%d) failed to ack sleep, ret=%d\n",
> > + domain->id, ret);
> > + }
>
> I don't think it's a great idea to wait for the power domain to go back
> to sleep; as long as we've cleared our wake bit, we should be free to
> move on with other work and not wait around for the punit to get around
> to taking action. We only need to make sure that the sleep has taken
> effect before the next time we grab the forcewake.
https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/218
>
> ...
> > diff --git a/drivers/gpu/drm/xe/xe_ggtt.c b/drivers/gpu/drm/xe/xe_ggtt.c
> > new file mode 100644
> > index 000000000000..3ace37d90f8d
> > --- /dev/null
> > +++ b/drivers/gpu/drm/xe/xe_ggtt.c
> > @@ -0,0 +1,284 @@
> > +// SPDX-License-Identifier: MIT
> > +/*
> > + * Copyright © 2021 Intel Corporation
> > + */
> > +
> > +#include "xe_ggtt.h"
> > +
> > +#include <linux/sizes.h>
> > +#include <drm/i915_drm.h>
> > +
> > +#include <drm/drm_managed.h>
> > +
> > +#include "xe_device.h"
> > +#include "xe_bo.h"
> > +#include "xe_gt.h"
> > +#include "xe_mmio.h"
> > +#include "xe_wopcm.h"
> > +
> > +#include "../i915/i915_reg.h"
> > +#include "../i915/gt/intel_gt_regs.h"
> > +
> > +/* FIXME: Common file, preferably auto-gen */
> > +#define MTL_GGTT_PTE_PAT0 BIT(52)
> > +#define MTL_GGTT_PTE_PAT1 BIT(53)
> > +
> > +u64 xe_ggtt_pte_encode(struct xe_bo *bo, u64 bo_offset)
> > +{
> > + struct xe_device *xe = xe_bo_device(bo);
> > + u64 pte;
> > + bool is_lmem;
> > +
> > + pte = xe_bo_addr(bo, bo_offset, GEN8_PAGE_SIZE, &is_lmem);
> > + pte |= GEN8_PAGE_PRESENT;
> > +
> > + if (is_lmem)
> > + pte |= GEN12_GGTT_PTE_LM;
> > +
> > + /* FIXME: vfunc + pass in caching rules */
> > + if (xe->info.platform == XE_METEORLAKE) {
> > + pte |= MTL_GGTT_PTE_PAT0;
> > + pte |= MTL_GGTT_PTE_PAT1;
> > + }
>
> This hardcodes PAT index 3, which is WB with 1-way coherency. That's
> probably how a lot of UMD buffers will get mapped in the PPGTT, but may
> not be suitable in all cases. There are some workarounds that require
> uncached in certain circumstances, and I think display generally wants
> uncached for the GGTT mapping.
>
> We need to figure out how cache behavior is going to be managed on the
> Xe driver in general. i915's mutable obj->cache_level is generally
> considered a big mistake now; I think the expectation was that we were
> going to track PAT index selection on the VMA now since that matches how
> the hardware tracks it and you can potentially have multiple mappings
> with different PAT settings.
we have a /* FIXME */ there,
but anyway:
https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/219
>
> ...
> > +void xe_ggtt_invalidate(struct xe_gt *gt)
> > +{
> > + /* TODO: vfunc for GuC vs. non-GuC */
> > +
> > + /* TODO: i915 makes comments about this being uncached and
> > + * therefore flushing WC buffers. Is that really true here?
> > + */
> > + xe_mmio_write32(gt, GFX_FLSH_CNTL_GEN6.reg, GFX_FLSH_CNTL_EN);
>
> This register went away in Xe_HP; we shouldn't be trying to write it on
> newer platforms. I'm not sure if there's an equivalent register located
> somewhere else now or not.
https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/220
>
> > + if (xe_device_guc_submission_enabled(gt_to_xe(gt))) {
> > + struct xe_device *xe = gt_to_xe(gt);
> > +
> > + /* TODO: also use vfunc here */
> > + if (xe->info.platform == XE_PVC) {
> > + xe_mmio_write32(gt, PVC_GUC_TLB_INV_DESC1.reg,
> > + PVC_GUC_TLB_INV_DESC1_INVALIDATE);
> > + xe_mmio_write32(gt, PVC_GUC_TLB_INV_DESC0.reg,
> > + PVC_GUC_TLB_INV_DESC0_VALID);
> > + } else
> > + xe_mmio_write32(gt, GEN12_GUC_TLB_INV_CR.reg,
> > + GEN12_GUC_TLB_INV_CR_INVALIDATE);
> > + }
> > +}
> ...
> > +void xe_ggtt_map_bo(struct xe_ggtt *ggtt, struct xe_bo *bo)
> > +{
> > + u64 start = bo->ggtt_node.start;
> > + u64 offset, pte;
> > +
> > + for (offset = 0; offset < bo->size; offset += GEN8_PAGE_SIZE) {
> > + pte = xe_ggtt_pte_encode(bo, offset);
> > + xe_ggtt_set_pte(ggtt, start + offset, pte);
> > + }
> > +
> > + xe_ggtt_invalidate(ggtt->gt);
>
> The GGTT is shared by two GTs on a platform like MTL; we only seem to be
> invalidating the GuC's TLB for the primary GT here and are overlooking
> the media GT.
added to the same bucket as the above one
https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/220
>
> ...
> > diff --git a/drivers/gpu/drm/xe/xe_gt.c b/drivers/gpu/drm/xe/xe_gt.c
> ...
> > +/* FIXME: These should be in a common file */
> > +#define CHV_PPAT_SNOOP REG_BIT(6)
> > +#define GEN8_PPAT_AGE(x) ((x)<<4)
> > +#define GEN8_PPAT_LLCeLLC (3<<2)
> > +#define GEN8_PPAT_LLCELLC (2<<2)
> > +#define GEN8_PPAT_LLC (1<<2)
>
> The ones above here aren't even used anywhere below.
>
> > +#define GEN8_PPAT_WB (3<<0)
> > +#define GEN8_PPAT_WT (2<<0)
> > +#define GEN8_PPAT_WC (1<<0)
> > +#define GEN8_PPAT_UC (0<<0)
> > +#define GEN8_PPAT_ELLC_OVERRIDE (0<<2)
>
> Also unused
>
> > +#define GEN8_PPAT(i, x) ((u64)(x) << ((i) * 8))
>
> Ditto
>
> > +#define GEN12_PPAT_CLOS(x) ((x)<<2)
>
> Only used on PVC, so this should have an XEHPC_ prefix rather than
> GEN12_.
>
> > +
> > +static void tgl_setup_private_ppat(struct xe_gt *gt)
> > +{
> > + /* TGL doesn't support LLC or AGE settings */
> > + xe_mmio_write32(gt, GEN12_PAT_INDEX(0).reg, GEN8_PPAT_WB);
> > + xe_mmio_write32(gt, GEN12_PAT_INDEX(1).reg, GEN8_PPAT_WC);
> > + xe_mmio_write32(gt, GEN12_PAT_INDEX(2).reg, GEN8_PPAT_WT);
> > + xe_mmio_write32(gt, GEN12_PAT_INDEX(3).reg, GEN8_PPAT_UC);
> > + xe_mmio_write32(gt, GEN12_PAT_INDEX(4).reg, GEN8_PPAT_WB);
> > + xe_mmio_write32(gt, GEN12_PAT_INDEX(5).reg, GEN8_PPAT_WB);
> > + xe_mmio_write32(gt, GEN12_PAT_INDEX(6).reg, GEN8_PPAT_WB);
> > + xe_mmio_write32(gt, GEN12_PAT_INDEX(7).reg, GEN8_PPAT_WB);
> > +}
> > +
> > +static void pvc_setup_private_ppat(struct xe_gt *gt)
> > +{
> > + xe_mmio_write32(gt, GEN12_PAT_INDEX(0).reg, GEN8_PPAT_UC);
> > + xe_mmio_write32(gt, GEN12_PAT_INDEX(1).reg, GEN8_PPAT_WC);
> > + xe_mmio_write32(gt, GEN12_PAT_INDEX(2).reg, GEN8_PPAT_WT);
> > + xe_mmio_write32(gt, GEN12_PAT_INDEX(3).reg, GEN8_PPAT_WB);
> > + xe_mmio_write32(gt, GEN12_PAT_INDEX(4).reg,
> > + GEN12_PPAT_CLOS(1) | GEN8_PPAT_WT);
> > + xe_mmio_write32(gt, GEN12_PAT_INDEX(5).reg,
> > + GEN12_PPAT_CLOS(1) | GEN8_PPAT_WB);
> > + xe_mmio_write32(gt, GEN12_PAT_INDEX(6).reg,
> > + GEN12_PPAT_CLOS(2) | GEN8_PPAT_WT);
> > + xe_mmio_write32(gt, GEN12_PAT_INDEX(7).reg,
> > + GEN12_PPAT_CLOS(2) | GEN8_PPAT_WB);
> > +}
> > +
> > +#define MTL_PPAT_L4_CACHE_POLICY_MASK REG_GENMASK(3, 2)
> > +#define MTL_PAT_INDEX_COH_MODE_MASK REG_GENMASK(1, 0)
> > +#define MTL_PPAT_3_UC REG_FIELD_PREP(MTL_PPAT_L4_CACHE_POLICY_MASK, 3)
> > +#define MTL_PPAT_1_WT REG_FIELD_PREP(MTL_PPAT_L4_CACHE_POLICY_MASK, 1)
> > +#define MTL_PPAT_0_WB REG_FIELD_PREP(MTL_PPAT_L4_CACHE_POLICY_MASK, 0)
> > +#define MTL_3_COH_2W REG_FIELD_PREP(MTL_PAT_INDEX_COH_MODE_MASK, 3)
> > +#define MTL_2_COH_1W REG_FIELD_PREP(MTL_PAT_INDEX_COH_MODE_MASK, 2)
> > +#define MTL_0_COH_NON REG_FIELD_PREP(MTL_PAT_INDEX_COH_MODE_MASK, 0)
> > +
> > +static void mtl_setup_private_ppat(struct xe_gt *gt)
> > +{
> > + xe_mmio_write32(gt, GEN12_PAT_INDEX(0).reg, MTL_PPAT_0_WB);
> > + xe_mmio_write32(gt, GEN12_PAT_INDEX(1).reg,
> > + MTL_PPAT_1_WT | MTL_2_COH_1W);
> > + xe_mmio_write32(gt, GEN12_PAT_INDEX(2).reg,
> > + MTL_PPAT_3_UC | MTL_2_COH_1W);
>
> Indices 1 and 2 shouldn't have the 1W coherency bit set.
>
> All of the register writes here should be switched to MCR writes in
> general to avoid racing with external agents who might be trying to
> perform unicast operations.
added all PAT setting issues to that bucket:
https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/219
>
> > + xe_mmio_write32(gt, GEN12_PAT_INDEX(3).reg,
> > + MTL_PPAT_0_WB | MTL_2_COH_1W);
> > + xe_mmio_write32(gt, GEN12_PAT_INDEX(4).reg,
> > + MTL_PPAT_0_WB | MTL_3_COH_2W);
> > +}
> ...
> > +static int gt_fw_domain_init(struct xe_gt *gt)
>
> Personally I find this name a bit confusing. I keep expecting this to
> be initialization of the GT forcewake domain, but it actually winds up
> being a subset of GT initialization that you want to do while holding
> the GT wake (the domain itself was already initialized earlier). Same
> comment for the all_fw_domain_init() farther down.
added to the fw bucket:
https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/218
>
> ...
> > +static int gt_reset(struct xe_gt *gt)
> > +{
> > + struct xe_device *xe = gt_to_xe(gt);
> > + int err;
> > +
> > + /* We only support GT resets with GuC submission */
> > + if (!xe_device_guc_submission_enabled(gt_to_xe(gt)))
> > + return -ENODEV;
> > +
> > + drm_info(&xe->drm, "GT reset started\n");
> > +
> > + xe_device_mem_access_get(gt_to_xe(gt));
> > + err = xe_force_wake_get(gt_to_fw(gt), XE_FORCEWAKE_ALL);
> > + if (err)
> > + goto err_msg;
> > +
> > + xe_uc_stop_prepare(>->uc);
> > + xe_gt_pagefault_reset(gt);
> > +
> > + err = xe_uc_stop(>->uc);
> > + if (err)
> > + goto err_out;
>
> Does resetting the GT inherently invalidate the TLBs? At this point
> we're not handling TLB invalidation requests anymore, so I'm not sure if
> that's a concern or not.
I believe this is a question to Matt Brost and Niranjana on their current
work around the TLB invalidations, which were not present in this first
squashed patch.
>
> ...
> > +int xe_gt_suspend(struct xe_gt *gt)
> > +{
> > + struct xe_device *xe = gt_to_xe(gt);
> > + int err;
> > +
> > + /* For now suspend/resume is only allowed with GuC */
> > + if (!xe_device_guc_submission_enabled(gt_to_xe(gt)))
> > + return -ENODEV;
> > +
> > + xe_device_mem_access_get(gt_to_xe(gt));
> > + err = xe_force_wake_get(gt_to_fw(gt), XE_FORCEWAKE_ALL);
> > + if (err)
> > + goto err_msg;
> > +
> > + err = xe_uc_suspend(>->uc);
> > + if (err)
> > + goto err_force_wake;
> > +
>
> Same question as above; if we bail out part way through the higher-level
> suspend process, but we've already stopped the GuC on a GT, is there any
> concern about not responding to any TLB invalidation requests that came
> in?
ditto
>
> ...
> > diff --git a/drivers/gpu/drm/xe/xe_guc_ads.c b/drivers/gpu/drm/xe/xe_guc_ads.c
> ...
> > +static unsigned int guc_mmio_regset_write(struct xe_guc_ads *ads,
> > + struct iosys_map *regset_map,
> > + struct xe_hw_engine *hwe)
> > +{
> > + struct xe_hw_engine *hwe_rcs_reset_domain =
> > + xe_gt_any_hw_engine_by_reset_domain(hwe->gt, XE_ENGINE_CLASS_RENDER);
> > + struct xe_reg_sr_entry *entry;
> > + unsigned long idx;
> > + unsigned count = 0;
> > + const struct {
> > + u32 reg;
> > + u32 flags;
> > + bool skip;
> > + } *e, extra_regs[] = {
> > + { .reg = RING_MODE_GEN7(hwe->mmio_base).reg, },
> > + { .reg = RING_HWS_PGA(hwe->mmio_base).reg, },
> > + { .reg = RING_IMR(hwe->mmio_base).reg, },
> > + { .reg = GEN12_RCU_MODE.reg, .flags = 0x3,
>
> The programming of RCU_MODE (i.e., enabling the CCS engines) should
> probably be handled through RTP now?
Not sure about that... but it looks like a good idea for more usage of the RTP.
https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/221
>
> ...
> > diff --git a/drivers/gpu/drm/xe/xe_hw_engine.c b/drivers/gpu/drm/xe/xe_hw_engine.c
> ...
> > +struct engine_info {
> > + const char *name;
> > + unsigned int class : 8;
> > + unsigned int instance : 8;
> > + enum xe_force_wake_domains domain;
> > + /* mmio bases table *must* be sorted in reverse graphics_ver order */
> > + struct engine_mmio_base {
> > + unsigned int graphics_ver : 8;
>
> We might need a full arch+release version here in the future?
I really hope that we don't need that.
Let's keep it simple until we have a real case...
>
> > + unsigned int base : 24;
> > + } mmio_bases[MAX_MMIO_BASES];
>
> At the moment the multiple bases we have can be dropped since they're
> for old platforms that the Xe driver doesn't support.
I'm not following here..
we have different bases per engine/cs... so I don't understand what
can be dropped.
>
> ...
> > diff --git a/drivers/gpu/drm/xe/xe_irq.c b/drivers/gpu/drm/xe/xe_irq.c
>
> There's lots of "gen3," "gen11," etc. in this file that should probably
> be cleaned up.
I believe some might still apply. But indeed let's clean that up at least
and also get ridden of 'gen'....
https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/222
>
> ...
> > diff --git a/drivers/gpu/drm/xe/xe_mmio.c b/drivers/gpu/drm/xe/xe_mmio.c
> ...
> > +static const i915_reg_t mmio_read_whitelist[] = {
> > + RING_TIMESTAMP(RENDER_RING_BASE),
> > +};
> > +
> > +int xe_mmio_ioctl(struct drm_device *dev, void *data,
> > + struct drm_file *file)
>
> My understanding is that having a register read ioctl was pretty much
> ancient history that was grandfathered into the i915 design. Is there
> any reason to keep this on Xe rather than just providing a more
> appropriate way to obtain the render timestamp (e.g., via the query
> ioctl or something)? Among other things, userspace needs to interpret
> the register value, which seems like something the kernel should really
> be doing for it; it's possible new fields could be added to the register
> in the future containing something we don't want to just blindly expose
> to userspace.
very good point.
Also these registers can be read with MI_LRI commands from userspace directly.
https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/223
>
> > +{
> > + struct xe_device *xe = to_xe_device(dev);
> > + struct drm_xe_mmio *args = data;
> > + unsigned int bits_flag, bytes;
> > + bool allowed;
> > + int ret = 0;
> > +
> > + if (XE_IOCTL_ERR(xe, args->extensions))
> > + return -EINVAL;
> > +
> > + if (XE_IOCTL_ERR(xe, args->flags & ~VALID_MMIO_FLAGS))
> > + return -EINVAL;
> > +
> > + if (XE_IOCTL_ERR(xe, !(args->flags & DRM_XE_MMIO_WRITE) && args->value))
> > + return -EINVAL;
> > +
> > + allowed = capable(CAP_SYS_ADMIN);
> > + if (!allowed && ((args->flags & ~DRM_XE_MMIO_BITS_MASK) == DRM_XE_MMIO_READ)) {
> > + unsigned int i;
> > +
> > + for (i = 0; i < ARRAY_SIZE(mmio_read_whitelist); i++) {
> > + if (mmio_read_whitelist[i].reg == args->addr) {
> > + allowed = true;
> > + break;
> > + }
> > + }
> > + }
> > +
> > + if (XE_IOCTL_ERR(xe, !allowed))
> > + return -EPERM;
> > +
> > + bits_flag = args->flags & DRM_XE_MMIO_BITS_MASK;
> > + bytes = 1 << bits_flag;
> > + if (XE_IOCTL_ERR(xe, args->addr + bytes > xe->mmio.size))
> > + return -EINVAL;
> > +
> > + xe_force_wake_get(gt_to_fw(&xe->gt[0]), XE_FORCEWAKE_ALL);
>
> Everywhere in this function is using xe->gt[0] or to_gt(xe), so it
> doesn't seem like this will work with multi-tile platforms.
added to the fw bucket:
https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/218
>
> > +
> > + if (args->flags & DRM_XE_MMIO_WRITE) {
> > + switch (bits_flag) {
> > + case DRM_XE_MMIO_8BIT:
> > + return -EINVAL; /* TODO */
> > + case DRM_XE_MMIO_16BIT:
> > + return -EINVAL; /* TODO */
> > + case DRM_XE_MMIO_32BIT:
> > + if (XE_IOCTL_ERR(xe, args->value > U32_MAX))
> > + return -EINVAL;
> > + xe_mmio_write32(to_gt(xe), args->addr, args->value);
> > + break;
> > + case DRM_XE_MMIO_64BIT:
> > + xe_mmio_write64(to_gt(xe), args->addr, args->value);
> > + break;
> > + default:
> > + drm_WARN(&xe->drm, 1, "Invalid MMIO bit size");
> > + ret = -EINVAL;
> > + goto exit;
> > + }
> > + }
> > +
> > + if (args->flags & DRM_XE_MMIO_READ) {
>
> Once we've made it past the 'allowed' check above, we're still trusting
> the user to pass the right register size. At the moment it doesn't
> matter too much since the only whitelisted register is 64-bit, but if we
> added something else that was 32-bit or smaller, userspace could still
> read extra register(s) by requesting 64-bit here.
ouch!
But this should be gone with the kill of the mmio read ioctl:
https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/223
>
> > + switch (bits_flag) {
> > + case DRM_XE_MMIO_8BIT:
> > + return -EINVAL; /* TODO */
> > + case DRM_XE_MMIO_16BIT:
> > + return -EINVAL; /* TODO */
> > + case DRM_XE_MMIO_32BIT:
> > + args->value = xe_mmio_read32(to_gt(xe), args->addr);
> > + break;
> > + case DRM_XE_MMIO_64BIT:
> > + args->value = xe_mmio_read64(to_gt(xe), args->addr);
>
> It looks like this becomes a simple readq() operation. I thought
> counter registers were exactly the type of registers where we needed to
> avoid doing that because 64-bit reads don't actually work as you'd
> expect and may give bogus data?
ditto
>
> ...
> > diff --git a/drivers/gpu/drm/xe/xe_mmio.h b/drivers/gpu/drm/xe/xe_mmio.h
> ...
> > +static inline u64 xe_mmio_read64(struct xe_gt *gt, u32 reg)
> > +{
> > + if (reg < gt->mmio.adj_limit)
> > + reg += gt->mmio.adj_offset;
> > +
> > + return readq(gt->mmio.regs + reg);
>
> As noted earlier, we generally don't want to be doing readq's on 64-bit
> registers. There are a lot of reports of one dword coming back
> properly, but the other one being all 0's or all F's. And even if both
> dwords come back in the read, the read itself isn't atomic for 64-bit
> registers, so trying to read a counter this way can give incorrect
> results.
>
> Also, having all of our register accesses happen on a 'gt' is kind of
> ugly since a lot of the platform's register accesses are completely
> unrelated to GT (i.e., sgunit, soc, display, etc.).
https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/224
>
> ...
> > diff --git a/drivers/gpu/drm/xe/xe_mocs.c b/drivers/gpu/drm/xe/xe_mocs.c
> ...
> > +static const struct xe_mocs_entry tgl_mocs_desc[] = {
> > + /*
> > + * NOTE:
> > + * Reserved and unspecified MOCS indices have been set to (L3 + LCC).
> > + * These reserved entries should never be used, they may be changed
> > + * to low performant variants with better coherency in the future if
> > + * more entries are needed. We are programming index XE_MOCS_PTE(1)
> > + * only, __init_mocs_table() take care to program unused index with
> > + * this entry.
> > + */
> > + MOCS_ENTRY(XE_MOCS_PTE,
> > + LE_0_PAGETABLE | LE_TC_0_PAGETABLE,
> > + L3_1_UC),
> > + GEN11_MOCS_ENTRIES,
>
> I think this entry is something we got stuck with on TGL because we
> screwed up the table and couldn't fix it after force_probe was removed
> for ABI reasons. But for the Xe driver we should just use the correct
> table (which I believe is already handled by the "gen12" table farther
> down); no need to repeat our i915 mistakes.
added to the caching bucket:
https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/219
>
> ...
> > + case XE_METEORLAKE:
> > + info->size = ARRAY_SIZE(dg2_mocs_desc);
> > + info->table = dg2_mocs_desc;
>
> We still need to land the proper MTL-specific table here.
added to the caching bucket:
https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/219
>
> ...
> > +void xe_mocs_init(struct xe_gt *gt)
> > +{
>
> In general it seems like we might be able to convert the MOCS
> programming over to use the RTP facility of the Xe driver?
added to the caching bucket:
https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/219
>
> ...
> > diff --git a/drivers/gpu/drm/xe/xe_pci.c b/drivers/gpu/drm/xe/xe_pci.c
> ...
> > +struct xe_subplatform_desc {
> > + enum xe_subplatform subplatform;
> > + const char *name;
> > + const u16 *pciidlist;
> > +};
>
> Just as a note, we're going to need to rework how platforms and
> subplatforms work (both in i915 and the xe driver). Once we have
> multiple GMD_ID platforms released the PCI IDs may start becoming
> unreliable with various mix-and-match combinations.
yeap! :/
>
> ...
> > +#define GEN13_DISPLAY \
>
> There's no such thing as "GEN13" so this name doesn't make sense.
> Probably should have been XE_LPD instead (i.e., display version 13).
>
> In general I want to look into moving the display feature flags and
> assignment of a display subtructure into the display code itself (rather
> than having the top-level i915/xe drivers set this up). I.e., the main
> driver would just call something like intel_display_init() and that
> centralized display code would check the PCI ID or GMD_ID to identify
> itself.
https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/225
>
> ...
> > diff --git a/drivers/gpu/drm/xe/xe_pt.c b/drivers/gpu/drm/xe/xe_pt.c
> ...
> > +static u64 __gen8_pte_encode(u64 pte, enum xe_cache_level cache, u32 flags,
> > + u32 pt_level)
> > +{
> > + pte |= GEN8_PAGE_PRESENT | GEN8_PAGE_RW;
> > +
> > + if (unlikely(flags & PTE_READ_ONLY))
> > + pte &= ~GEN8_PAGE_RW;
> > +
> > + /* FIXME: I don't think the PPAT handling is correct for MTL */
>
> Yeah, the PAT encoding for MTL needs updates. But also, I think the
> enum xe_cache_level is something we probably want to rethink. That's
> similar to what i915 did, which is causing us all kinds of headaches
> now. For PPGTT mappings, userspace should already know exactly what PAT
> behavior they want (just like they know what MOCS behavior they want)
> and they can pass us the specific index to encode (presumably at vm_bind
> time so that it's attached to the specific gtt mapping, not the object).
>
added to the caching bucket:
https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/219
> ...
> > diff --git a/drivers/gpu/drm/xe/xe_query.c b/drivers/gpu/drm/xe/xe_query.c
> ...
> > +static int query_gts(struct xe_device *xe, struct drm_xe_device_query *query)
>
> On i915 we were specifically asked to steer clear of "gts" because it
> confuses people as to whether its some new three-letter acronym, or
> whether it's the plural form of "gt." I assume the maintainers will
> want us to avoid it in Xe as well.
good point... but I believe this also depends on what we decide for the
rigth naming of the 'gt' itself?!
Thank you so much for the review and putting all of these together.
>
>
> Matt
>
> --
> Matt Roper
> Graphics Software Engineer
> Linux GPU Platform Enablement
> Intel Corporation
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