[igt-dev] [v2] tests/kms_color: Fix CRC mismatch issues with ctm test

[Lionel Landwerlin]

On 25/03/2019 06:36, Shankar, Uma wrote:
>
>> -----Original Message-----
>> From: Landwerlin, Lionel G
>> Sent: Monday, March 25, 2019 7:11 AM
>> To: Shankar, Uma <uma.shankar at intel.com>; igt-dev at lists.freedesktop.org
>> Cc: Syrjala, Ville <ville.syrjala at intel.com>; Lankhorst, Maarten
>> <maarten.lankhorst at intel.com>
>> Subject: Re: [igt-dev] [v2] tests/kms_color: Fix CRC mismatch issues with ctm test
>>
>> When degamma & gamma LUTs are disabled & CTM is enabled, i915 programs a
>> linear table in the degamma/gamma LUTs :
>>
>> https://cgit.freedesktop.org/drm/drm-
>> intel/tree/drivers/gpu/drm/i915/intel_color.c#n463
>> https://cgit.freedesktop.org/drm/drm-
>> intel/tree/drivers/gpu/drm/i915/intel_color.c#n495
>>
>> All the values programmed are in u16 range which is also what userspace can
>> program (this applies to BDW/SKL/KBL).
>> What is it that the kernel is able to program but not userspace?
> Hi Lionel,
> Issue is with representing 1.0 which needs a 3.16 kind of representation. So directly doing it in
> Kernel to program linear luts using below:
> for (i = 0; i < lut_size; i++) {
> 			u32 v = (i * (1 << 16)) / (lut_size - 1);
> 			I915_WRITE(PRE_CSC_GAMC_DATA(pipe), v);
> 		}
> takes care of the corner case. The ABI is getting extended and we will need higher
> precision luts, but for now due to lack of it,  putting the same to be done in driver.
>
> Regards,
> Uma Shankar


Hi Uma,

This is for GLK right?
What about the failures on KBL/SKL?

There the hardware doesn't have fixed point values.

Thanks,

-Lionel


>
>> -Lionel
>>
>> On 24/03/2019 17:55, Uma Shankar wrote:
>>> Due to Gamma/Degamma limitation with precision (lack of exact 1.0
>>> representation) due to ABI restriction, applying 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.
>>>
>>> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=108147
>>> Signed-off-by: Uma Shankar <uma.shankar at intel.com>
>>> ---
>>>    tests/kms_color.c | 16 ++++++++++++++--
>>>    1 file changed, 14 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/tests/kms_color.c b/tests/kms_color.c index
>>> decf3c2..93560d4 100644
>>> --- a/tests/kms_color.c
>>> +++ b/tests/kms_color.c
>>> @@ -696,8 +696,15 @@ 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);
>>> +		}
>>> +
>>>    		disable_ctm(primary->pipe);
>>>    		igt_display_commit(&data->display);
>>>
>>> @@ -1005,6 +1012,11 @@ run_tests_for_pipe(data_t *data, enum pipe p)
>>>    		 * produce with an 8 bits per color framebuffer. */
>>>    		igt_require(!IS_CHERRYVIEW(data->devid));
>>>
>>> +		/* Disable and let default luts be applied by kernel */
>>> +		disable_degamma(primary->pipe);
>>> +		disable_gamma(primary->pipe);
>>> +		igt_display_commit(&data->display);
>>> +
>>>    		igt_assert(test_pipe_ctm(data, primary, red_green_blue,
>>>    					 full_rgb, ctm));
>>>    	}