[PATCH v2 1/2] drm/xe: Probe for tile count during device info initialization
Cavitt, Jonathan
jonathan.cavitt at intel.com
Mon Jul 28 18:33:04 UTC 2025
-----Original Message-----
From: Sousa, Gustavo <gustavo.sousa at intel.com>
Sent: Monday, July 28, 2025 11:29 AM
To: intel-xe at lists.freedesktop.org
Cc: Cavitt, Jonathan <jonathan.cavitt at intel.com>; Sousa, Gustavo <gustavo.sousa at intel.com>
Subject: [PATCH v2 1/2] drm/xe: Probe for tile count during device info initialization
>
> The function mmio_multi_tile_setup() does not look like the proper
> location for probing for the number of existing tiles in the hardware.
> It should not be that function's responsibility and such information
> should instead be already available when it gets called.
>
> The fact that we need to adjust gt_count is a symptom of that.
>
> Move probing of available tile count to a dedicated function named
> xe_info_probe_tile_count() and call it from xe_info_init(), which seems
> like a more appropriate place for that.
>
> With that move, we no longer need to (and shouldn't) adjust gt_count as
> a part of xe_info_probe_tile_count(), as that field will be initialized
> later in xe_info_init().
>
> v2:
> - Use KUnit static stub so that we do not try to query hardware when
> running KUnit tests. (CI)
> - Tweak last paragraph of commit message to make it clearer.
> (Jonathan)
>
> Reviewed-by: Jonathan Cavitt <jonathan.cavitt at intel.com> #v1
> Signed-off-by: Gustavo Sousa <gustavo.sousa at intel.com>
> ---
> drivers/gpu/drm/xe/tests/xe_pci.c | 7 +++++++
> drivers/gpu/drm/xe/xe_mmio.c | 33 ---------------------------------
> drivers/gpu/drm/xe/xe_pci.c | 34 ++++++++++++++++++++++++++++++++++
> 3 files changed, 41 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/gpu/drm/xe/tests/xe_pci.c b/drivers/gpu/drm/xe/tests/xe_pci.c
> index 9c715e59f030..db30c5156d0c 100644
> --- a/drivers/gpu/drm/xe/tests/xe_pci.c
> +++ b/drivers/gpu/drm/xe/tests/xe_pci.c
> @@ -101,6 +101,11 @@ static void fake_read_gmdid(struct xe_device *xe, enum xe_gmdid_type type,
> }
> }
>
> +static void fake_xe_info_probe_tile_count(struct xe_device *xe)
> +{
> + /* Nothing to do, just use the statically defined value. */
> +}
> +
> int xe_pci_fake_device_init(struct xe_device *xe)
> {
> struct kunit *test = kunit_get_current_test();
> @@ -138,6 +143,8 @@ int xe_pci_fake_device_init(struct xe_device *xe)
> data->sriov_mode : XE_SRIOV_MODE_NONE;
>
> kunit_activate_static_stub(test, read_gmdid, fake_read_gmdid);
> + kunit_activate_static_stub(test, xe_info_probe_tile_count,
> + fake_xe_info_probe_tile_count);
>
> xe_info_init_early(xe, desc, subplatform_desc);
> xe_info_init(xe, desc);
> diff --git a/drivers/gpu/drm/xe/xe_mmio.c b/drivers/gpu/drm/xe/xe_mmio.c
> index e4db8d58ea2d..ef6f3ea573a2 100644
> --- a/drivers/gpu/drm/xe/xe_mmio.c
> +++ b/drivers/gpu/drm/xe/xe_mmio.c
> @@ -58,7 +58,6 @@ static void tiles_fini(void *arg)
> static void mmio_multi_tile_setup(struct xe_device *xe, size_t tile_mmio_size)
> {
> struct xe_tile *tile;
> - struct xe_gt *gt;
> u8 id;
>
> /*
> @@ -68,38 +67,6 @@ static void mmio_multi_tile_setup(struct xe_device *xe, size_t tile_mmio_size)
> if (xe->info.tile_count == 1)
> return;
>
> - /* Possibly override number of tile based on configuration register */
> - if (!xe->info.skip_mtcfg) {
> - struct xe_mmio *mmio = xe_root_tile_mmio(xe);
> - u8 tile_count, gt_count;
> - u32 mtcfg;
> -
> - /*
> - * Although the per-tile mmio regs are not yet initialized, this
> - * is fine as it's going to the root tile's mmio, that's
> - * guaranteed to be initialized earlier in xe_mmio_probe_early()
> - */
> - mtcfg = xe_mmio_read32(mmio, XEHP_MTCFG_ADDR);
> - tile_count = REG_FIELD_GET(TILE_COUNT, mtcfg) + 1;
> -
> - if (tile_count < xe->info.tile_count) {
> - drm_info(&xe->drm, "tile_count: %d, reduced_tile_count %d\n",
> - xe->info.tile_count, tile_count);
> - xe->info.tile_count = tile_count;
> -
> - /*
> - * We've already setup gt_count according to the full
> - * tile count. Re-calculate it to only include the GTs
> - * that belong to the remaining tile(s).
> - */
> - gt_count = 0;
> - for_each_gt(gt, xe, id)
> - if (gt->info.id < tile_count * xe->info.max_gt_per_tile)
> - gt_count++;
> - xe->info.gt_count = gt_count;
> - }
> - }
> -
> for_each_remote_tile(tile, xe, id)
> xe_mmio_init(&tile->mmio, tile, xe->mmio.regs + id * tile_mmio_size, SZ_4M);
> }
> diff --git a/drivers/gpu/drm/xe/xe_pci.c b/drivers/gpu/drm/xe/xe_pci.c
> index 52d46c66ae1e..0d7073a04bb2 100644
> --- a/drivers/gpu/drm/xe/xe_pci.c
> +++ b/drivers/gpu/drm/xe/xe_pci.c
> @@ -17,6 +17,7 @@
>
> #include "display/xe_display.h"
> #include "regs/xe_gt_regs.h"
> +#include "regs/xe_regs.h"
> #include "xe_device.h"
> #include "xe_drv.h"
> #include "xe_gt.h"
> @@ -604,6 +605,37 @@ static int xe_info_init_early(struct xe_device *xe,
> return 0;
> }
>
> +/*
> + * Possibly override number of tile based on configuration register.
> + */
> +static void xe_info_probe_tile_count(struct xe_device *xe)
> +{
> + struct xe_mmio *mmio;
> + u8 tile_count;
> + u32 mtcfg;
> +
> + KUNIT_STATIC_STUB_REDIRECT(xe_info_probe_tile_count, xe);
I don't know much about these static stubs, but if they're necessary
to make CI happy and don't have any functional impact otherwise,
then I won't block on it.
Everything else is the same from V1 (code-wise), so my Reviewed-by
still stands.
-Jonathan Cavitt
> +
> + if (xe->info.skip_mtcfg)
> + return;
> +
> + mmio = xe_root_tile_mmio(xe);
> +
> + /*
> + * Although the per-tile mmio regs are not yet initialized, this
> + * is fine as it's going to the root tile's mmio, that's
> + * guaranteed to be initialized earlier in xe_mmio_probe_early()
> + */
> + mtcfg = xe_mmio_read32(mmio, XEHP_MTCFG_ADDR);
> + tile_count = REG_FIELD_GET(TILE_COUNT, mtcfg) + 1;
> +
> + if (tile_count < xe->info.tile_count) {
> + drm_info(&xe->drm, "tile_count: %d, reduced_tile_count %d\n",
> + xe->info.tile_count, tile_count);
> + xe->info.tile_count = tile_count;
> + }
> +}
> +
> /*
> * Initialize device info content that does require knowledge about
> * graphics / media IP version.
> @@ -678,6 +710,8 @@ static int xe_info_init(struct xe_device *xe,
> xe->info.has_usm = graphics_desc->has_usm;
> xe->info.has_64bit_timestamp = graphics_desc->has_64bit_timestamp;
>
> + xe_info_probe_tile_count(xe);
> +
> for_each_remote_tile(tile, xe, id) {
> int err;
>
>
> --
> 2.50.1
>
>
More information about the Intel-xe
mailing list