[igt-dev] [PATCH i-g-t] tests/i915/kms_big_fb: trigger async flip with a dummy flip

[Murthy, Arun R]

> On 6/28/2022 4:34 PM, Arun R Murthy wrote:
> > In oder to trigger the async flip, a dummy flip is required after sync
> > flip so as to update the watermarks for async in KMD which happens as
> > part of this dummy flip. Thereafter async memory update will act as a
> > trigger register.
> > Capturing the CRC is done after the async flip as async flip at some
> > times can consume fairly a vblank period time.
> >
> > Signed-off-by: Arun R Murthy <arun.r.murthy at intel.com>
> > ---
> >   tests/i915/kms_big_fb.c | 29 +++++++++++++++++++----------
> >   1 file changed, 19 insertions(+), 10 deletions(-)
> >
> > diff --git a/tests/i915/kms_big_fb.c b/tests/i915/kms_big_fb.c index
> > d50fde45..6caf3c31 100644
> > --- a/tests/i915/kms_big_fb.c
> > +++ b/tests/i915/kms_big_fb.c
> > @@ -465,7 +465,7 @@ static bool test_pipe(data_t *data)
> >   static bool
> >   max_hw_stride_async_flip_test(data_t *data)
> >   {
> > -	uint32_t ret, startframe;
> > +	uint32_t ret, frame;
> >   	const uint32_t w = data->output->config.default_mode.hdisplay,
> >   		       h = data->output->config.default_mode.vdisplay;
> >   	igt_plane_t *primary;
> > @@ -519,7 +519,19 @@ max_hw_stride_async_flip_test(data_t *data)
> >
> DRM_MODE_ATOMIC_ALLOW_MODESET, NULL);
> >
> >   		igt_wait_for_vblank(data->drm_fd, data-
> >display.pipes[primary->pipe->pipe].crtc_offset);
> > -		startframe = kmstest_get_vblank(data->drm_fd, data->pipe,
> 0) + 1;
> > +		/*
> > +		 * In older platforms (<= Gen10), async address update bit is
> double buffered.
> > +		 * So flip timestamp can be verified only from the second flip.
> > +		 * The first async flip just enables the async address update.
> > +		 * In platforms greater than DISPLAY13 the first async flip will
> be discarded
> > +		 * in order to change the watermark levels as per the
> optimization. Hence the
> > +		 * subsequent async flips will actually do the asynchronous
> flips.
> > +		 */
> > +		ret = drmModePageFlip(data->drm_fd, data->output-
> >config.crtc->crtc_id,
> > +						      data->big_fb_flip[i].fb_id,
> > +
> DRM_MODE_PAGE_FLIP_ASYNC, NULL);
> > +		igt_wait_for_vblank(data->drm_fd, data-
> >display.pipes[primary->pipe->pipe].crtc_offset);
> > +		frame = kmstest_get_vblank(data->drm_fd, data->pipe, 0) +
> 1;
> 
> Hi,
> 
> Should this be added inside a gen check similar to kms_async_flips?

Yes sorry missed it!

> 
> >
> >   		for (int j = 0; j < 2; j++) {
> >   			do {
> > @@ -528,23 +540,20 @@ max_hw_stride_async_flip_test(data_t *data)
> >
> DRM_MODE_PAGE_FLIP_ASYNC, NULL);
> >   			} while (ret == -EBUSY);
> >   			igt_assert(ret == 0);
> > +			igt_pipe_crc_get_for_frame(data->drm_fd, data-
> >pipe_crc,
> > +					   frame, &compare_crc);
> >
> > +			frame = kmstest_get_vblank(data->drm_fd, data-
> >pipe, 0) + 1;
> >   			do {
> >   				ret = drmModePageFlip(data->drm_fd, data-
> >output->config.crtc->crtc_id,
> >   						      data->big_fb.fb_id,
> >
> DRM_MODE_PAGE_FLIP_ASYNC, NULL);
> >   			} while (ret == -EBUSY);
> >   			igt_assert(ret == 0);
> > +			igt_pipe_crc_get_for_frame(data->drm_fd, data-
> >pipe_crc,
> > +					   frame, &async_crc);
> 
> We should be moving this IMHO. By waiting for vblank after each async flip
> to capture CRC, what is the intended result? Seems to be completely
> changing the existing test logic.

We are getting the vblank count and based on that getting the crc. Now we know for async flip at
certain times it can consume a time equivalent to a vblank period. So in those scenarios getting crc
based on the vblank goes for a toss. Hence capturing the vblank start time stamp at the beginning
of each flip.

> 
> Also, seems like we are overwriting the CRC captured for j = 0, as comparison
> is done outside this loop. Is this done on purpose?

Now with the changing the vblank start frame capture being added before the async flip, CRC can
be captured outside the loop as well, but makes no sense. To maintain this order moving the CRC
Capture also after each frame.

Thanks and Regards,
Arun R Murthy
--------------------