Re: [igt-dev] [PATCH i-g-t] igt/tests/kms_dp_tiled_display.c : kms test file for display port tiled displays

["Ser, Simon" <simon.ser@intel.com>]

wOn Wed, 2019-08-14 at 15:05 -0700, Tolakanahalli Pradeep, Madhumitha wrote:
> On Wed, 2019-08-14 at 14:43 +0100, Ser, Simon wrote:
> > On Wed, 2019-08-07 at 18:10 -0700, Tolakanahalli Pradeep, Madhumitha
> > wrote:
> > > > > I believe tests in kms_flip do a similar check. The
> > > > > page_flip_handler
> > > > > function handles the page flip event (which is given the flip
> > > > > timestamp
> > > > > and sequence number). check_state verifies that the timestamp
> > > > > is
> > > > > close
> > > > > enough to what we expect (in our atomic check, maybe we can
> > > > > compare
> > > > > with strict equality).
> > > > > 
> > > > > Since we're dealing with multiple CRTCs, it may be a good idea
> > > > > to
> > > > > use
> > > > > drmEventContext.version = 3 with page_flip_handler2 so that we
> > > > > also
> > > > > get
> > > > > the CRTC in the page flip handler. Version 3 is a core DRM
> > > > > feature,
> > > > > all
> > > > > drivers support it given a recent enough kernel.
> > > > > 
> > > > > Rough pseudo-code:
> > > > > 
> > > > > 	/* When committing buffer, request a page flip */
> > > > > 	drmModeAtomicCommit(fd, req, DRM_MODE_ATOMIC_NONBLOCK |
> > > > > 			    DRM_MODE_PAGE_FLIP_EVENT, data);
> > > > 
> > > > Here we do the modese with igt_display_commit2 call that then
> > > > calls
> > > > drmModeAtomicCommit but
> > > > doesnt call it with Page flip, do we have another igt helper that
> > > > does a atomic commit with
> > > > page flip event?
> > > > 
> > > > Can we not just do atomic commit and get vblank events so for two
> > > > crtcs we get two events and compare
> > > > the timestamp and make sure they are close enough?
> > 
> > I believe doing an atomic commit with DRM_MODE_PAGE_FLIP_EVENT as
> > Madhumitha suggested should be enough.
> 
> Looks like using DRM_MODE_PAGE_FLIP_EVENT is giving me a errno 22,
> invalid argument.

Have you tried DRM_MODE_PAGE_FLIP_EVENT | DRM_MODE_ATOMIC_NONBLOCK?

Enabling verbose dmesg DRM logging can help figuring out why the kernel
sends "invalid ar"EINVAL:

    echo 0x00 | sudo tee /sys/module/drm/parameters/debug

> > > > Manasi
> > > > 
> > > > > 	static void page_flip_handler(int fd, unsigned seq,
> > > > > 				      unsigned tv_sec,
> > > > > 				      unsigned tv_usec,
> > > > > 				      unsigned crtc_id, void
> > > > > *data)
> > > > > 	{
> > > > > 		/* Compare params with the other page flip */
> > > > > 	}
> > > > > 
> > > > > 	/* When we get POLLIN in the DRM FD */
> > > > > 	drmEventContext event = {
> > > > > 		.version = 3,
> > > > > 		.page_flip_handler2 = page_flip_handler,
> > > > > 	};
> > > > > 	drmHandleEvent(fd, &event);
> > > > > 
> > > 
> > > I was trying to implement the above code with igt_display_commit2.
> > > Looks like I'm timing out while poll-ing for POLLIN.
> > > 
> > > Is there something I could be doing wrong? According to my
> > > understanding, igt_display_commit2 should cause a page-flip event
> > > right?
> > 
> > Hmm. Yeah, it should work, assuming you use DRM_MODE_PAGE_FLIP_EVENT
> > when doing the atomic commit. Can you push your code somewhere (e.g.
> > on
> > a GitLab fork) so that I can have a look?
> 
> Sure!
> Here is the link to my forked repository. The commit and polling is in
> igt_main().
> https://gitlab.freedesktop.org/mtolakan/igt-gpu-tools
> My suspicion is the commit is not asynchronous, which is why I am unble
> to capture the page flip event. Please do let me know what you think,
> thanks!
> 
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