Re: [igt-dev] [PATCH v2 1/2] tests/kms_vrr: Use atomic API for page flip

["Navare, Manasi" <manasi.d.navare@intel.com>]

On Thu, Aug 06, 2020 at 12:02:04AM -0700, Modem, Bhanuprakash wrote:
> > -----Original Message-----
> > From: Navare, Manasi <manasi.d.navare@intel.com>
> > Sent: Thursday, August 6, 2020 12:41 AM
> > To: Modem, Bhanuprakash <bhanuprakash.modem@intel.com>
> > Cc: igt-dev@lists.freedesktop.org; Harry Wentland
> > <harry.wentland@amd.com>; Nicholas Kazlauskas
> > <nicholas.kazlauskas@amd.com>
> > Subject: Re: [PATCH v2 1/2] tests/kms_vrr: Use atomic API for page flip
> >
> > On Thu, Aug 06, 2020 at 12:05:05AM +0530, Bhanuprakash Modem wrote:
> > > We should avoid using drmModePageFlip as it'll only be used for
> > > legacy drivers, instead, use igt_display_commit_atomic() API to
> > > page flip for atomic display code path.
> > >
> > > v2:
> > > * Look for the page flip event not for the vblank event (Nicholas)
> >
> > Where have you done this change to wait for page flip event instead of
> > vblank event?
> > I thought we would need to change the function get_vblank_event_ns() for
> > this, I dont see
> > that change below, may be I am missing something?
> [Bhanu] I think no need to change the logic in get_vblank_event_ns(). May be we can have extra check (like "ev.base.type == event") to make sure we are reading the correct event.
> 
> Call flow:
> 1) drmWaitVBlank --> get_vblank_event_ns(): will get the DRM_EVENT_VBLANK event timestamp
> 2) igt_display_commit_atomic(DRM_MODE_PAGE_FLIP_EVENT) --> get_vblank_event_ns(): will get the DRM_EVENT_FLIP_COMPLETE event timestamp

Okay yes this makes sense now, would be better to explain this call flow in the get_vblank_event_ns()
function header somewhere and yes good idea to make its name generic, get_kernel_event_ns()
and explain that it could be either vblank event or flip event with the above call flow.
And also explain why we should care here for flip event rather than vblank.
Because vblank is triggered after each frame but depending on vblank evasion time
flip might or might not happen in that same frame, so capture flip event.

Manasi

> 
> Yeah, we can rename the get_vblank_event_ns() in a generic way like get_event_ns()
> >
> > @Nicholas, have you tested the AMD stack with the page flip event
> > timestamp deltas
> > instead of the vblank event timetsmap deltas and does that work?
> >
> > Manasi
> >
> > > * Fix to flip with different FBs (Bhanu)
> > >
> > > Cc: Harry Wentland <harry.wentland@amd.com>
> > > Cc: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
> > > Cc: Manasi Navare <manasi.d.navare@intel.com>
> > > Signed-off-by: Bhanuprakash Modem <bhanuprakash.modem@intel.com>
> > > ---
> > >  tests/kms_vrr.c | 45 +++++++++++++++++----------------------------
> > >  1 file changed, 17 insertions(+), 28 deletions(-)
> > >
> > > diff --git a/tests/kms_vrr.c b/tests/kms_vrr.c
> > > index 559ef203..b433a12e 100644
> > > --- a/tests/kms_vrr.c
> > > +++ b/tests/kms_vrr.c
> > > @@ -47,6 +47,7 @@ typedef struct range {
> > >  typedef struct data {
> > >  igt_display_t display;
> > >  int drm_fd;
> > > +igt_plane_t *primary;
> > >  igt_fb_t fb0;
> > >  igt_fb_t fb1;
> > >  } data_t;
> > > @@ -126,11 +127,11 @@ static range_t get_vrr_range(data_t *data,
> > igt_output_t *output)
> > >  }
> > >
> > >  /* Returns a suitable vrr test frequency. */
> > > -static uint32_t get_test_rate_ns(data_t *data, igt_output_t *output)
> > > +static uint64_t get_test_rate_ns(data_t *data, igt_output_t *output)
> > >  {
> > >  drmModeModeInfo *mode = igt_output_get_mode(output);
> > >  range_t range;
> > > -uint32_t vtest;
> > > +uint64_t vtest;
> > >
> > >  /*
> > >   * The frequency with the fastest convergence speed should be
> > > @@ -165,7 +166,6 @@ static void set_vrr_on_pipe(data_t *data, enum pipe
> > pipe, bool enabled)
> > >  static void prepare_test(data_t *data, igt_output_t *output, enum pipe
> > pipe)
> > >  {
> > >  drmModeModeInfo mode = *igt_output_get_mode(output);
> > > -igt_plane_t *primary;
> > >  cairo_t *cr;
> > >
> > >  /* Reset output */
> > > @@ -189,8 +189,8 @@ static void prepare_test(data_t *data, igt_output_t
> > *output, enum pipe pipe)
> > >  igt_put_cairo_ctx(cr);
> > >
> > >  /* Take care of any required modesetting before the test begins. */
> > > -primary = igt_output_get_plane_type(output, DRM_PLANE_TYPE_PRIMARY);
> > > -igt_plane_set_fb(primary, &data->fb0);
> > > +data->primary = igt_output_get_plane_type(output,
> > DRM_PLANE_TYPE_PRIMARY);
> > > +igt_plane_set_fb(data->primary, &data->fb0);
> > >
> > >  igt_display_commit_atomic(&data->display,
> > >    DRM_MODE_ATOMIC_ALLOW_MODESET, NULL);
> > > @@ -210,32 +210,25 @@ wait_for_vblank(data_t *data, enum pipe pipe)
> > >  return get_vblank_event_ns(data);
> > >  }
> > >
> > > -/* Performs an asynchronous non-blocking page-flip on a pipe. */
> > > -static int
> > > -do_flip(data_t *data, enum pipe pipe_id, igt_fb_t *fb)
> > > +/* Performs an atomic non-blocking page-flip on a pipe. */
> > > +static void
> > > +do_flip(data_t *data, igt_fb_t *fb)
> > >  {
> > > -igt_pipe_t *pipe = &data->display.pipes[pipe_id];
> > > -int ret;
> > > +int ret = 0;
> > >
> > >  igt_set_timeout(1, "Scheduling page flip\n");
> > >
> > > -/*
> > > - * Only the legacy flip ioctl supports async flips.
> > > - * It's also non-blocking, but returns -EBUSY if flipping too fast.
> > > - * 2x monitor tests will need async flips in the atomic API.
> > > - */
> > > +igt_plane_set_fb(data->primary, fb);
> > > +
> > >  do {
> > > -ret = drmModePageFlip(data->drm_fd, pipe->crtc_id,
> > > -      fb->fb_id,
> > > -      DRM_MODE_PAGE_FLIP_EVENT |
> > > -      DRM_MODE_PAGE_FLIP_ASYNC,
> > > -      data);
> > > +igt_display_commit_atomic(&data->display,
> > > +  DRM_MODE_ATOMIC_NONBLOCK |
> > > +  DRM_MODE_PAGE_FLIP_EVENT,
> > > +  data);
> > >  } while (ret == -EBUSY);
> > >
> > >  igt_assert_eq(ret, 0);
> > >  igt_reset_timeout();
> > > -
> > > -return 0;
> > >  }
> > >
> > >  /*
> > > @@ -246,11 +239,6 @@ do_flip(data_t *data, enum pipe pipe_id, igt_fb_t
> > *fb)
> > >   * can arbitrarily restrict the bounds further than the absolute
> > >   * min and max range. But VRR is really about extending the flip
> > >   * to prevent stuttering or to match a source content rate.
> > > - *
> > > - * The only way to "present" at a fixed rate like userspace in a vendor
> > > - * neutral manner is to do it with async flips. This avoids the need
> > > - * to wait for next vblank and it should eventually converge at the
> > > - * desired rate.
> > >   */
> > >  static uint32_t
> > >  flip_and_measure(data_t *data, igt_output_t *output, enum pipe pipe,
> > > @@ -269,7 +257,7 @@ flip_and_measure(data_t *data, igt_output_t *output,
> > enum pipe pipe,
> > >  int64_t diff_ns;
> > >
> > >  front = !front;
> > > -do_flip(data, pipe, front ? &data->fb1 : &data->fb0);
> > > +do_flip(data, front ? &data->fb1 : &data->fb0);
> > >
> > >  vblank_ns = get_vblank_event_ns(data);
> > >  diff_ns = rate_ns - (vblank_ns - last_vblank_ns);
> > > @@ -359,6 +347,7 @@ test_basic(data_t *data, enum pipe pipe,
> > igt_output_t *output, uint32_t flags)
> > >       "Target VRR off threshold exceeded, result was %u%%\n",
> > >       result);
> > >
> > > +igt_plane_set_fb(data->primary, NULL);
> > >  igt_remove_fb(data->drm_fd, &data->fb1);
> > >  igt_remove_fb(data->drm_fd, &data->fb0);
> > >  }
> > > --
> > > 2.20.1
> > >
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