Re: [igt-dev] [v4] tests/kms_color: Fix CRC mismatch issues with ctm test

[Daniel Vetter <daniel@ffwll.ch>]

On Fri, Mar 29, 2019 at 02:49:15AM +0530, Uma Shankar wrote:
> Due to Gamma/Degamma limitation with precision (lack of
> exact 1.0 representation) due to ABI restriction, applying

Huh, why? That sounds like a conversion bug in our gamma table handler.
0xffff == 1.0 if we don't treat it like that that's a driver bug. The
gamma table is _not_ fixed point, but linear range from 0-0xffff. Which is
unlike the ctm (which due to an uapi accident has a really hilarious fixed
point with sign bit format).

Please don't paper over driver bugs :-)
-Daniel

> linear gamma affects crc. This patch fixes the same by making
> ctm tests independant of gamma/degamma.
> 
> v2: Disable degamma/gamma programming for ctm max test as it
> leads to crc mimsmatch. Limiting it to this test case alone as
> other tests need it to be enabled, hence not touching those
> scenarios.
> 
> v3: Fixed a fumble with compilation.
> 
> v4: Disabling degamma and gamma for ctm max tests, after the logic
> in kernel has been updated by Ville's series.
> 
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=108147
> Signed-off-by: Uma Shankar <uma.shankar@intel.com>
> ---
>  tests/kms_color.c | 15 +++++++++++++--
>  1 file changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/tests/kms_color.c b/tests/kms_color.c
> index decf3c2..0951ffc 100644
> --- a/tests/kms_color.c
> +++ b/tests/kms_color.c
> @@ -696,8 +696,19 @@ static bool test_pipe_ctm(data_t *data,
>  		igt_assert(fb_modeset_id);
>  		igt_plane_set_fb(primary, &fb_modeset);
>  
> -		set_degamma(data, primary->pipe, degamma_linear);
> -		set_gamma(data, primary->pipe, gamma_linear);
> +		/*
> +		 * Don't program LUT's for max CTM cases as limitation of
> +		 * representing 1.0 due to ABI limits causes crc mismatch
> +		 */
> +		if (memcmp(before, after, sizeof(color_t))) {
> +			set_degamma(data, primary->pipe, degamma_linear);
> +			set_gamma(data, primary->pipe, gamma_linear);
> +		} else {
> +			/* Disable Degamma and Gamma for ctm max test */
> +			disable_degamma(primary->pipe);
> +			disable_gamma(primary->pipe);
> +		}
> +
>  		disable_ctm(primary->pipe);
>  		igt_display_commit(&data->display);
>  
> -- 
> 1.9.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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