[igt-dev] [Intel-gfx] [PATCH i-g-t v2] tests/kms_crtc_background_color: overhaul for latest ABI proposal (v2)

[Matt Roper]

On Tue, Nov 13, 2018 at 11:43:12PM +0000, Lionel Landwerlin wrote:
> On 13/11/2018 23:22, Matt Roper wrote:
> > It's worth noting that we don't seem to be able to test this feature
> > with CRC's.  Originally we wanted to draw a color into a plane's FB
> > (with Cairo) and then compare the CRC to turning off all planes and just
> > setting the CRTC background to the same color.  However the precision
> > and rounding of the color components causes the CRC's to come out
> > differently, even though the end result is visually identical.  So at
> > the moment this test is mainly useful for visual inspection in
> > interactive mode.
> Hey Matt,
> Out of curiosity, are the CRCs different only when with 16bpc? Or with 8bpc
> too?

Both 8 and 16 give different CRC's.  I suspect it's because cairo
handles the color values (which get passed as double) slightly
differently internally, although I haven't ruled out a slight inaccuracy
on the hardware side.  Given the alpha problems on gen9/gen10, it
wouldn't surprise me if it turns out that our hardware is also treating
a 10bpc component of 0x3ff as 0.999 rather than 1.0.


Matt

> 
> Thanks,
> 
> -
> Lionel
> 
> 
> 

-- 
Matt Roper
Graphics Software Engineer
IoTG Platform Enabling & Development
Intel Corporation
(916) 356-2795