[PATCH v2 5/5] drm/vkms: Implement CRC debugfs API
Sean Paul
seanpaul at chromium.org
Tue Jul 17 20:43:16 UTC 2018
On Tue, Jul 17, 2018 at 02:52:20AM +0300, Haneen Mohammed wrote:
> On Mon, Jul 16, 2018 at 02:22:56PM -0400, Sean Paul wrote:
> > On Sat, Jul 14, 2018 at 03:23:32PM +0300, Haneen Mohammed wrote:
> > > Implement the set_crc_source() callback.
> > > Compute CRC using crc32 on the visible part of the framebuffer.
> > > Use ordered workqueue 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,
> > >
> > > Signed-off-by: Haneen Mohammed <hamohammed.sa at gmail.com>
> >
> > Hey Haneen,
> > Thanks for revising this patch set. Things are looking good across the series,
> > just a few more comments :-)
> >
>
> Thank you so much for the review!
>
> > > ---
> > > Changes in v2:
> > > - Include this patch in this patchset.
> > >
> > > drivers/gpu/drm/vkms/Makefile | 2 +-
> > > drivers/gpu/drm/vkms/vkms_crtc.c | 60 ++++++++++++++++++++++++++-----
> > > drivers/gpu/drm/vkms/vkms_drv.c | 1 +
> > > drivers/gpu/drm/vkms/vkms_drv.h | 21 +++++++++++
> > > drivers/gpu/drm/vkms/vkms_plane.c | 10 ++++++
> > > 5 files changed, 85 insertions(+), 9 deletions(-)
> > >
> > > 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_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c
> > > index 26babb85ca77..f3a674db33b8 100644
> > > --- a/drivers/gpu/drm/vkms/vkms_crtc.c
> > > +++ b/drivers/gpu/drm/vkms/vkms_crtc.c
> > > @@ -10,18 +10,36 @@
> > > #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;
> > >
> > > + int crc_enabled = 0;
> > > +
> > > + spin_lock(&output->lock);
> > > + crc_enabled = output->crc_enabled;
> >
> > Aside from the implicit bool -> int cast, I don't think you need this local var,
> > just use output->crc_enabled directly below.
> >
> > > ret = drm_crtc_handle_vblank(crtc);
> > > if (!ret)
> > > DRM_ERROR("vkms failure on handling vblank");
> >
> > This would be more useful with the error code printed.
> >
>
> I think this only returns false on failure. Also I've noticed most of the usage of
> drm_crtc_handle_vblank don't check the return value, should I do the
> same as well and drop ret and error message?
Ahh, I didn't see that ret was bool. In that case, the error message is fine.
It's always good practice to assume that if a function returns a status, it's
worth checking.
>
> > >
> > > + if (state && 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);
> > >
> > > @@ -97,6 +115,8 @@ 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;
> > > }
> > >
> > > @@ -104,11 +124,18 @@ static void vkms_atomic_crtc_destroy_state(struct drm_crtc *crtc,
> > > struct drm_crtc_state *state)
> > > {
> > > struct vkms_crtc_state *vkms_state;
> > > + struct vkms_output *vkms_out = drm_crtc_to_vkms_output(crtc);
> > >
> > > vkms_state = to_vkms_crtc_state(state);
> > >
> > > __drm_atomic_helper_crtc_destroy_state(state);
> > > - kfree(vkms_state);
> > > +
> > > + if (vkms_state) {
> > > + flush_workqueue(vkms_out->crc_workq);
> >
> > I'm a little worried about this bit. Since the workqueue is per-output, is it
> > possible you'll be waiting for more frames to complete than you need to be?
> >
>
> I see, maybe I should flush per work_struct instead?
Yeah, that would make more sense IMO.
>
> > > + drm_framebuffer_put(&vkms_state->data.fb);
> > > + memset(&vkms_state->data, 0, sizeof(struct vkms_crc_data));
> > > + kfree(vkms_state);
> > > + }
> > > }
> > >
> > > static const struct drm_crtc_funcs vkms_crtc_funcs = {
> > > @@ -120,6 +147,7 @@ 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,
> > > @@ -134,26 +162,37 @@ 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);
> > > +
> > > + spin_lock_irq(&vkms_output->lock);
> >
> > Hmm, you can't lock across atomic_begin/flush. What is this protecting against?
> >
>
> I did this per Daniel recommendation:
> 1- spin_lock_irq -> vkms_crtc_atomic_begin
> 2- update vkms_crc_data and get ref to fb -> vkms_primary_plane_update
> 3- spin_unlock_irq after vblank event -> vkms_crtc_atomic_flush
I think I'm interpreting his mail a little differently. The point of the
spinlock is to protect the pointer to the crc_data in vkms_crtc (right now it's
not a pointer, but it should be).
So I think you need to do the following:
- Change crc_data to a pointer
- In plane_update, allocate new memory to hold crc_data and, under the spinlock,
update the crc_data to point to the new memory (add a WARN_ON if the pointer
is NULL)
- In the hrtimer, while holding the spinlock, take the pointer from crc_data
into a local variable and clear the crtc->crc_data pointer
- Pass the pointer (from the local variable) to the crc_worker
I don't think you need to hold the spinlock across the atomic hooks, just grab
it in plane_update.
Sean
>
> > > +}
> > > +
> > > static void vkms_crtc_atomic_flush(struct drm_crtc *crtc,
> > > struct drm_crtc_state *old_crtc_state)
> > > {
> > > - unsigned long flags;
> > > + struct vkms_output *vkms_output = drm_crtc_to_vkms_output(crtc);
> > >
> > > if (crtc->state->event) {
> > > - spin_lock_irqsave(&crtc->dev->event_lock, flags);
> > > + spin_lock(&crtc->dev->event_lock);
> >
> > What's the rationale behind this change?
> >
>
> hm I am not sure if this is correct, but I assume because spin_lock_irq in atomic_begin
> would disable interrupts and since this is before we unlock vkms_output->lock with
> spin_unlock_irq so irqsave here is not necessary?
>
Once you limit the scope of the spinlock above, you will want to revert this
change.
> > >
> > > if (drm_crtc_vblank_get(crtc) != 0)
> > > drm_crtc_send_vblank_event(crtc, crtc->state->event);
> > > else
> > > drm_crtc_arm_vblank_event(crtc, crtc->state->event);
> > >
> > > - spin_unlock_irqrestore(&crtc->dev->event_lock, flags);
> > > + spin_unlock(&crtc->dev->event_lock);
> > >
> > > 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 +201,7 @@ 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 +213,9 @@ 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 37aa2ef33b21..5d78bd97e69c 100644
> > > --- a/drivers/gpu/drm/vkms/vkms_drv.c
> > > +++ b/drivers/gpu/drm/vkms/vkms_drv.c
> > > @@ -46,6 +46,7 @@ static void vkms_release(struct drm_device *dev)
> > > platform_device_unregister(vkms->platform);
> > > 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 bf811d0ec349..95985649768c 100644
> > > --- a/drivers/gpu/drm/vkms/vkms_drv.h
> > > +++ b/drivers/gpu/drm/vkms/vkms_drv.h
> > > @@ -20,12 +20,23 @@ static const u32 vkms_formats[] = {
> > > DRM_FORMAT_XRGB8888,
> > > };
> > >
> > > +struct vkms_crc_data {
> > > + struct drm_rect src;
> > > + struct drm_framebuffer fb;
> > > +};
> > > +
> > > /**
> > > * vkms_crtc_state - Driver specific CRTC state
> > > * @base: base CRTC state
> > > + * @crc_work: work struct to compute and add CRC entries
> > > + * @data: data required for CRC computation
> > > + * @n_frame: frame number for computed CRC
> > > */
> > > struct vkms_crtc_state {
> > > struct drm_crtc_state base;
> > > + struct work_struct crc_work;
> > > + struct vkms_crc_data data;
> > > + unsigned int n_frame;
> > > };
> > >
> > > struct vkms_output {
> > > @@ -35,6 +46,11 @@ struct vkms_output {
> > > struct hrtimer vblank_hrtimer;
> > > ktime_t period_ns;
> > > struct drm_pending_vblank_event *event;
> > > + bool crc_enabled;
> >
> > Where is this set to true?
> >
>
> Oh sorry I forgot to add a vkms_crc.c which sets crc_enabled in
> set_crc_source callback!
>
> I'll work on fixing the issues you mentioned here and the other patches
> as well, thank you so much again!
Thanks for working through this!
Sean
> Haneen
>
> > > + /* ordered wq for crc_work */
> > > + struct workqueue_struct *crc_workq;
> > > + /* protects concurrent access to crc_data */
> > > + spinlock_t lock;
> > > };
> > >
> > > struct vkms_device {
> > > @@ -95,4 +111,9 @@ void *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 aaf7c35faed6..1e0ee8ca8bd6 100644
> > > --- a/drivers/gpu/drm/vkms/vkms_plane.c
> > > +++ b/drivers/gpu/drm/vkms/vkms_plane.c
> > > @@ -24,6 +24,16 @@ 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_crtc_state *state;
> > > +
> > > + if (!plane->state->crtc || !plane->state->fb)
> > > + return;
> > > +
> > > + state = to_vkms_crtc_state(plane->state->crtc->state);
> > > + memcpy(&state->data.src, &plane->state->src, sizeof(struct drm_rect));
> > > + memcpy(&state->data.fb, plane->state->fb,
> > > + sizeof(struct drm_framebuffer));
> > > + drm_framebuffer_get(&state->data.fb);
> > > }
> > >
> > > static int vkms_plane_atomic_check(struct drm_plane *plane,
> > > --
> > > 2.17.1
> > >
> >
> > --
> > Sean Paul, Software Engineer, Google / Chromium OS
--
Sean Paul, Software Engineer, Google / Chromium OS
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