[Intel-gfx] [PATCH igt] igt/kms_flip: Calibrate timestamp errors

[Chris Wilson]

On Mon, Oct 24, 2016 at 11:14:31AM +0200, Daniel Vetter wrote:
> On Mon, Oct 24, 2016 at 09:54:52AM +0100, Chris Wilson wrote:
> Also with this patch we should be able to throw out the hacks for tv-out.
> I only added those because the reported mode-timings are massively off
> (due to the magic tv scaler thing) from the real timestamps we receive.
> Auto-detecting this is much better.

Not quite just yet, we need to split the timing tests into a subgroup
with a subtest per output so that we can skip one without skipping the
others. At the moment, this check makes it bail out on my ctg/ilk who
have a difference of about 50us between measured and expected vblank
interval on LVDS (which is nigh on impossible given our confidence in the
measurement, i.e. about 7 sigma).
 
> And another issue: Failing to match the reported mode timings is a driver
> bug.

Not quite, remember we override the user for fixed mode panels. But yes,
piglit also has a similar expectation that the dotclock we report (via
GetMscRate) in someway corresponds to actual vblank interval.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre