[PATCH v2 2/2] drm/vkms: Implement CRC debugfs API
Sean Paul
seanpaul at chromium.org
Fri Aug 3 16:42:15 UTC 2018
On Thu, Aug 02, 2018 at 08:09:51AM -0300, Gustavo Padovan wrote:
> Hi Haneen,
>
> On Thu, Aug 02, 2018 at 04:10:26AM +0300, Haneen Mohammed wrote:
> > This patch implement the necessary functions to compute and add CRCs
> > entries:
> >
> > - Implement the set_crc_source() callback.
> > - Compute CRC using crc32 on the visible part of the framebuffer.
> > - Use ordered workqueue per output to compute and add CRC at the end
> > of a vblank.
> > - Use appropriate synchronization methods since the CRC computation must
> > be atomic wrt the generated vblank event for a given atomic update, by
> > using spinlock across atomic_begin/atomic_flush to wrap the event
> > handling code completely and match the flip event with the CRC.
> >
> > Since vkms_crc_work_handle() can sleep, spinlock can't be acquired
> > while accessing vkms_output->primary_crc to compute CRC.
> > To make sure the data is updated and released without conflict with
> > the vkms_crc_work_handle(), the work_struct is flushed @crtc_destroy
> > and the data is updated before scheduling the work handle again, as
> > follow:
>
> I'm not sure I get why this is a spinlock and not a mutex. With the
> later you are able to sleep. Also, your spinlock held through the whole
> atomic commit (from the begin to flush) which seems too much time for
> busy waiting. Or am I missing something here?
I expressed some of the same concerns here:
https://lists.freedesktop.org/archives/dri-devel/2018-July/183584.html
The tl;dr is that the spinlock is required so we can acquire it in the vblank
hrtimer. It is held across begin/flush to prevent sending vblank eventss until
the crc has been fully calculated for the frame. More details in the thread,
ofc.
Sean
>
> Gustavo
>
> >
> > * CRC data update:
> > 1- store vkms_crc_data {fb, src} per plane_state
> > 2- @plane_duplicate_state -> allocate vkms_crc_data
> > 3- during atomic commit (@atomic_update) ->
> > a) copy {fb, src} to plane_state->crc_data
> > b) get reference to fb,
> > 3- @plane_destroy_state -> a) if (fb refcount) remove reference to fb
> > b) deallocate crc_data
> >
> > * Atomic Commit:
> > 1- vkms_plane_atomic_check
> > 2- vkms_prepare_fb -> vmap vkms_gem_obj->vaddr
> > 3- atomic_begin -> hold crc spinlock
> > 4- atomic_plane_update -> a) update vkms_output->primary_crc
> > b) get reference to fb
> > 5- atomic_flush -> a) send vblank event while holding event_lock
> > b) release crc spinlock
> >
> > * hrtimer regular callback:
> > 1- hold crc spinlock
> > 2- drm_crtc_handle_vblank()
> > 3- queue vkms_crc_work_handle
> > 4- release crc spinlock
> >
> > * cleanup:
> > 1- @cleanup_fb ->vunmap vkms_gem_obj->vaddr
> > 2- @crtc_destroy -> flush work struct
> > 3- @plane_destroy -> a) if (fb refcount) remove reference to fb
> > b) deallocate crc_data
> >
> > Signed-off-by: Haneen Mohammed <hamohammed.sa at gmail.com>
> > ---
> > Changes in v2:
> > - remove vkms_crc_data for primary plane from vkms_output
> > and access it from vkms_plane_state instead.
> > - flush crc_workq in vkms_set_crc_source before changing out->enabled
> > value.
> >
> > drivers/gpu/drm/vkms/Makefile | 2 +-
> > drivers/gpu/drm/vkms/vkms_crc.c | 95 +++++++++++++++++++++++++++++++
> > drivers/gpu/drm/vkms/vkms_crtc.c | 56 +++++++++++++++---
> > drivers/gpu/drm/vkms/vkms_drv.c | 1 +
> > drivers/gpu/drm/vkms/vkms_drv.h | 21 +++++++
> > drivers/gpu/drm/vkms/vkms_plane.c | 30 ++++++++++
> > 6 files changed, 196 insertions(+), 9 deletions(-)
> > create mode 100644 drivers/gpu/drm/vkms/vkms_crc.c
> >
> > diff --git a/drivers/gpu/drm/vkms/Makefile b/drivers/gpu/drm/vkms/Makefile
> > index 986297da51bf..37966914f70b 100644
> > --- a/drivers/gpu/drm/vkms/Makefile
> > +++ b/drivers/gpu/drm/vkms/Makefile
> > @@ -1,3 +1,3 @@
> > -vkms-y := vkms_drv.o vkms_plane.o vkms_output.o vkms_crtc.o vkms_gem.o
> > +vkms-y := vkms_drv.o vkms_plane.o vkms_output.o vkms_crtc.o vkms_gem.o vkms_crc.o
> >
> > obj-$(CONFIG_DRM_VKMS) += vkms.o
> > diff --git a/drivers/gpu/drm/vkms/vkms_crc.c b/drivers/gpu/drm/vkms/vkms_crc.c
> > new file mode 100644
> > index 000000000000..9b909221943f
> > --- /dev/null
> > +++ b/drivers/gpu/drm/vkms/vkms_crc.c
> > @@ -0,0 +1,95 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +#include "vkms_drv.h"
> > +#include <linux/crc32.h>
> > +#include <drm/drm_gem_framebuffer_helper.h>
> > +
> > +static uint32_t _vkms_get_crc(struct vkms_crc_data *crc_data)
> > +{
> > + struct drm_framebuffer *fb = &crc_data->fb;
> > + struct drm_gem_object *gem_obj = drm_gem_fb_get_obj(fb, 0);
> > + struct vkms_gem_object *vkms_obj = drm_gem_to_vkms_gem(gem_obj);
> > + u32 crc = 0;
> > + int i = 0;
> > + unsigned int x = crc_data->src.x1 >> 16;
> > + unsigned int y = crc_data->src.y1 >> 16;
> > + unsigned int height = drm_rect_height(&crc_data->src) >> 16;
> > + unsigned int width = drm_rect_width(&crc_data->src) >> 16;
> > + unsigned int cpp = fb->format->cpp[0];
> > + unsigned int src_offset;
> > + unsigned int size_byte = width * cpp;
> > + void *vaddr;
> > +
> > + mutex_lock(&vkms_obj->pages_lock);
> > + vaddr = vkms_obj->vaddr;
> > + if (WARN_ON(!vaddr))
> > + return crc;
> > +
> > + for (i = y; i < y + height; i++) {
> > + src_offset = fb->offsets[0] + (i * fb->pitches[0]) + (x * cpp);
> > + crc = crc32_le(crc, vaddr + src_offset, size_byte);
> > + }
> > + mutex_unlock(&vkms_obj->pages_lock);
> > +
> > + return crc;
> > +}
> > +
> > +void vkms_crc_work_handle(struct work_struct *work)
> > +{
> > + struct vkms_crtc_state *crtc_state = container_of(work,
> > + struct vkms_crtc_state,
> > + crc_work);
> > + struct drm_crtc *crtc = crtc_state->base.crtc;
> > + struct vkms_output *out = drm_crtc_to_vkms_output(crtc);
> > + struct vkms_device *vdev = container_of(out, struct vkms_device,
> > + output);
> > + struct vkms_crc_data *primary_crc = NULL;
> > + struct drm_plane *plane;
> > +
> > + u32 crc32 = 0;
> > +
> > + drm_for_each_plane(plane, &vdev->drm) {
> > + struct vkms_plane_state *vplane_state;
> > + struct vkms_crc_data *crc_data;
> > +
> > + vplane_state = to_vkms_plane_state(plane->state);
> > + crc_data = vplane_state->crc_data;
> > +
> > + if (drm_framebuffer_read_refcount(&crc_data->fb) == 0)
> > + continue;
> > +
> > + if (plane->type == DRM_PLANE_TYPE_PRIMARY) {
> > + primary_crc = crc_data;
> > + break;
> > + }
> > + }
> > +
> > + if (primary_crc)
> > + crc32 = _vkms_get_crc(primary_crc);
> > +
> > + drm_crtc_add_crc_entry(crtc, true, crtc_state->n_frame, &crc32);
> > +}
> > +
> > +int vkms_set_crc_source(struct drm_crtc *crtc, const char *src_name,
> > + size_t *values_cnt)
> > +{
> > + struct vkms_output *out = drm_crtc_to_vkms_output(crtc);
> > + bool enabled = false;
> > + unsigned long flags;
> > + int ret = 0;
> > +
> > + if (src_name && strcmp(src_name, "auto") == 0)
> > + enabled = true;
> > + else if (src_name)
> > + ret = -EINVAL;
> > +
> > + *values_cnt = 1;
> > +
> > + /* make sure nothing is scheduled on crtc workq */
> > + flush_workqueue(out->crc_workq);
> > +
> > + spin_lock_irqsave(&out->lock, flags);
> > + out->crc_enabled = enabled;
> > + spin_unlock_irqrestore(&out->lock, flags);
> > +
> > + return ret;
> > +}
> > diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c
> > index 26babb85ca77..a6c080d7f7ae 100644
> > --- a/drivers/gpu/drm/vkms/vkms_crtc.c
> > +++ b/drivers/gpu/drm/vkms/vkms_crtc.c
> > @@ -10,18 +10,33 @@
> > #include <drm/drm_atomic_helper.h>
> > #include <drm/drm_crtc_helper.h>
> >
> > -static enum hrtimer_restart vkms_vblank_simulate(struct hrtimer *timer)
> > +static void _vblank_handle(struct vkms_output *output)
> > {
> > - struct vkms_output *output = container_of(timer, struct vkms_output,
> > - vblank_hrtimer);
> > struct drm_crtc *crtc = &output->crtc;
> > - int ret_overrun;
> > + struct vkms_crtc_state *state = to_vkms_crtc_state(crtc->state);
> > bool ret;
> >
> > + spin_lock(&output->lock);
> > ret = drm_crtc_handle_vblank(crtc);
> > if (!ret)
> > DRM_ERROR("vkms failure on handling vblank");
> >
> > + if (state && output->crc_enabled) {
> > + state->n_frame = drm_crtc_accurate_vblank_count(crtc);
> > + queue_work(output->crc_workq, &state->crc_work);
> > + }
> > +
> > + spin_unlock(&output->lock);
> > +}
> > +
> > +static enum hrtimer_restart vkms_vblank_simulate(struct hrtimer *timer)
> > +{
> > + struct vkms_output *output = container_of(timer, struct vkms_output,
> > + vblank_hrtimer);
> > + int ret_overrun;
> > +
> > + _vblank_handle(output);
> > +
> > ret_overrun = hrtimer_forward_now(&output->vblank_hrtimer,
> > output->period_ns);
> >
> > @@ -97,18 +112,22 @@ vkms_atomic_crtc_duplicate_state(struct drm_crtc *crtc)
> >
> > __drm_atomic_helper_crtc_duplicate_state(crtc, &vkms_state->base);
> >
> > + INIT_WORK(&vkms_state->crc_work, vkms_crc_work_handle);
> > +
> > return &vkms_state->base;
> > }
> >
> > static void vkms_atomic_crtc_destroy_state(struct drm_crtc *crtc,
> > struct drm_crtc_state *state)
> > {
> > - struct vkms_crtc_state *vkms_state;
> > -
> > - vkms_state = to_vkms_crtc_state(state);
> > + struct vkms_crtc_state *vkms_state = to_vkms_crtc_state(state);
> >
> > __drm_atomic_helper_crtc_destroy_state(state);
> > - kfree(vkms_state);
> > +
> > + if (vkms_state) {
> > + flush_work(&vkms_state->crc_work);
> > + kfree(vkms_state);
> > + }
> > }
> >
> > static const struct drm_crtc_funcs vkms_crtc_funcs = {
> > @@ -120,6 +139,7 @@ static const struct drm_crtc_funcs vkms_crtc_funcs = {
> > .atomic_destroy_state = vkms_atomic_crtc_destroy_state,
> > .enable_vblank = vkms_enable_vblank,
> > .disable_vblank = vkms_disable_vblank,
> > + .set_crc_source = vkms_set_crc_source,
> > };
> >
> > static void vkms_crtc_atomic_enable(struct drm_crtc *crtc,
> > @@ -134,9 +154,21 @@ static void vkms_crtc_atomic_disable(struct drm_crtc *crtc,
> > drm_crtc_vblank_off(crtc);
> > }
> >
> > +static void vkms_crtc_atomic_begin(struct drm_crtc *crtc,
> > + struct drm_crtc_state *old_crtc_state)
> > +{
> > + struct vkms_output *vkms_output = drm_crtc_to_vkms_output(crtc);
> > +
> > + /* This lock is held across the atomic commit to block vblamk timer
> > + * from scheduling vkms_crc_work_handle until the crc_data is updated
> > + */
> > + spin_lock_irq(&vkms_output->lock);
> > +}
> > +
> > static void vkms_crtc_atomic_flush(struct drm_crtc *crtc,
> > struct drm_crtc_state *old_crtc_state)
> > {
> > + struct vkms_output *vkms_output = drm_crtc_to_vkms_output(crtc);
> > unsigned long flags;
> >
> > if (crtc->state->event) {
> > @@ -151,9 +183,12 @@ static void vkms_crtc_atomic_flush(struct drm_crtc *crtc,
> >
> > crtc->state->event = NULL;
> > }
> > +
> > + spin_unlock_irq(&vkms_output->lock);
> > }
> >
> > static const struct drm_crtc_helper_funcs vkms_crtc_helper_funcs = {
> > + .atomic_begin = vkms_crtc_atomic_begin,
> > .atomic_flush = vkms_crtc_atomic_flush,
> > .atomic_enable = vkms_crtc_atomic_enable,
> > .atomic_disable = vkms_crtc_atomic_disable,
> > @@ -162,6 +197,7 @@ static const struct drm_crtc_helper_funcs vkms_crtc_helper_funcs = {
> > int vkms_crtc_init(struct drm_device *dev, struct drm_crtc *crtc,
> > struct drm_plane *primary, struct drm_plane *cursor)
> > {
> > + struct vkms_output *vkms_out = drm_crtc_to_vkms_output(crtc);
> > int ret;
> >
> > ret = drm_crtc_init_with_planes(dev, crtc, primary, cursor,
> > @@ -173,5 +209,9 @@ int vkms_crtc_init(struct drm_device *dev, struct drm_crtc *crtc,
> >
> > drm_crtc_helper_add(crtc, &vkms_crtc_helper_funcs);
> >
> > + spin_lock_init(&vkms_out->lock);
> > +
> > + vkms_out->crc_workq = alloc_ordered_workqueue("vkms_crc_workq", 0);
> > +
> > return ret;
> > }
> > diff --git a/drivers/gpu/drm/vkms/vkms_drv.c b/drivers/gpu/drm/vkms/vkms_drv.c
> > index e340aa128b61..519a353cd909 100644
> > --- a/drivers/gpu/drm/vkms/vkms_drv.c
> > +++ b/drivers/gpu/drm/vkms/vkms_drv.c
> > @@ -79,6 +79,7 @@ static void vkms_release(struct drm_device *dev)
> > drm_atomic_helper_shutdown(&vkms->drm);
> > drm_mode_config_cleanup(&vkms->drm);
> > drm_dev_fini(&vkms->drm);
> > + destroy_workqueue(vkms->output.crc_workq);
> > }
> >
> > static struct drm_driver vkms_driver = {
> > diff --git a/drivers/gpu/drm/vkms/vkms_drv.h b/drivers/gpu/drm/vkms/vkms_drv.h
> > index a1b206643c10..de1ddf31341b 100644
> > --- a/drivers/gpu/drm/vkms/vkms_drv.h
> > +++ b/drivers/gpu/drm/vkms/vkms_drv.h
> > @@ -20,20 +20,31 @@ static const u32 vkms_formats[] = {
> > DRM_FORMAT_XRGB8888,
> > };
> >
> > +struct vkms_crc_data {
> > + struct drm_rect src;
> > + struct drm_framebuffer fb;
> > +};
> > +
> > /**
> > * vkms_plane_state - Driver specific plane state
> > * @base: base plane state
> > + * @crc_data: data required for CRC computation
> > */
> > struct vkms_plane_state {
> > struct drm_plane_state base;
> > + struct vkms_crc_data *crc_data;
> > };
> >
> > /**
> > * vkms_crtc_state - Driver specific CRTC state
> > * @base: base CRTC state
> > + * @crc_work: work struct to compute and add CRC entries
> > + * @n_frame: frame number for computed CRC
> > */
> > struct vkms_crtc_state {
> > struct drm_crtc_state base;
> > + struct work_struct crc_work;
> > + unsigned int n_frame;
> > };
> >
> > struct vkms_output {
> > @@ -43,6 +54,11 @@ struct vkms_output {
> > struct hrtimer vblank_hrtimer;
> > ktime_t period_ns;
> > struct drm_pending_vblank_event *event;
> > + bool crc_enabled;
> > + /* ordered wq for crc_work */
> > + struct workqueue_struct *crc_workq;
> > + /* protects concurrent access to crc_data */
> > + spinlock_t lock;
> > };
> >
> > struct vkms_device {
> > @@ -106,4 +122,9 @@ int vkms_gem_vmap(struct drm_gem_object *obj);
> >
> > void vkms_gem_vunmap(struct drm_gem_object *obj);
> >
> > +/* CRC Support */
> > +int vkms_set_crc_source(struct drm_crtc *crtc, const char *src_name,
> > + size_t *values_cnt);
> > +void vkms_crc_work_handle(struct work_struct *work);
> > +
> > #endif /* _VKMS_DRV_H_ */
> > diff --git a/drivers/gpu/drm/vkms/vkms_plane.c b/drivers/gpu/drm/vkms/vkms_plane.c
> > index 70fca22bc51b..c91661631c76 100644
> > --- a/drivers/gpu/drm/vkms/vkms_plane.c
> > +++ b/drivers/gpu/drm/vkms/vkms_plane.c
> > @@ -16,11 +16,18 @@ static struct drm_plane_state *
> > vkms_plane_duplicate_state(struct drm_plane *plane)
> > {
> > struct vkms_plane_state *vkms_state;
> > + struct vkms_crc_data *crc_data;
> >
> > vkms_state = kzalloc(sizeof(*vkms_state), GFP_KERNEL);
> > if (!vkms_state)
> > return NULL;
> >
> > + crc_data = kzalloc(sizeof(*crc_data), GFP_KERNEL);
> > + if (WARN_ON(!crc_data))
> > + DRM_INFO("Couldn't allocate crc_data");
> > +
> > + vkms_state->crc_data = crc_data;
> > +
> > __drm_atomic_helper_plane_duplicate_state(plane,
> > &vkms_state->base);
> >
> > @@ -31,6 +38,18 @@ static void vkms_plane_destroy_state(struct drm_plane *plane,
> > struct drm_plane_state *old_state)
> > {
> > struct vkms_plane_state *vkms_state = to_vkms_plane_state(old_state);
> > + struct drm_crtc *crtc = vkms_state->base.crtc;
> > +
> > + if (crtc) {
> > + /* dropping the reference we acquired in
> > + * vkms_primary_plane_update()
> > + */
> > + if (drm_framebuffer_read_refcount(&vkms_state->crc_data->fb))
> > + drm_framebuffer_put(&vkms_state->crc_data->fb);
> > + }
> > +
> > + kfree(vkms_state->crc_data);
> > + vkms_state->crc_data = NULL;
> >
> > __drm_atomic_helper_plane_destroy_state(old_state);
> > kfree(vkms_state);
> > @@ -65,6 +84,17 @@ static const struct drm_plane_funcs vkms_plane_funcs = {
> > static void vkms_primary_plane_update(struct drm_plane *plane,
> > struct drm_plane_state *old_state)
> > {
> > + struct vkms_plane_state *vkms_plane_state;
> > + struct vkms_crc_data *crc_data;
> > +
> > + if (!plane->state->crtc || !plane->state->fb)
> > + return;
> > +
> > + vkms_plane_state = to_vkms_plane_state(plane->state);
> > + crc_data = vkms_plane_state->crc_data;
> > + memcpy(&crc_data->src, &plane->state->src, sizeof(struct drm_rect));
> > + memcpy(&crc_data->fb, plane->state->fb, sizeof(struct drm_framebuffer));
> > + drm_framebuffer_get(&crc_data->fb);
> > }
> >
> > static int vkms_plane_atomic_check(struct drm_plane *plane,
> > --
> > 2.17.1
> >
--
Sean Paul, Software Engineer, Google / Chromium OS
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