[Intel-gfx] [v3] drm/i915: Fix Limited Range Color Handling

[Shankar, Uma]

>-----Original Message-----
>From: Ville Syrjälä [mailto:ville.syrjala at linux.intel.com]
>Sent: Tuesday, January 30, 2018 8:53 PM
>To: Shankar, Uma <uma.shankar at intel.com>
>Cc: intel-gfx at lists.freedesktop.org; Lin, Johnson <johnson.lin at intel.com>;
>Syrjala, Ville <ville.syrjala at intel.com>; Lankhorst, Maarten
><maarten.lankhorst at intel.com>
>Subject: Re: [Intel-gfx] [v3] drm/i915: Fix Limited Range Color Handling
>
>On Tue, Jan 30, 2018 at 08:49:22PM +0530, Uma Shankar wrote:
>> From: Johnson Lin <johnson.lin at intel.com>
>>
>> Some panels support limited range output (16-235) compared to full
>> range RGB values (0-255). Also userspace can control the RGB range
>> using "Broadcast RGB" property. Currently the code to handle full
>> range to limited range is broken. This patch fixes the same by
>> properly scaling down all the full range co-efficients with limited
>> range scaling factor.
>>
>> v2: Fixed Ville's review comments.
>>
>> v3: Changed input to const and used correct data types as
>>     suggested by Ville
>>
>> Signed-off-by: Johnson Lin <johnson.lin at intel.com>
>> Signed-off-by: Uma Shankar <uma.shankar at intel.com>
>> Reviewed-by: Ville Syrjä <ville.syrjala at linux.intel.com>
>
>Name fail.
>

Have updated this.

>> ---
>>  drivers/gpu/drm/i915/intel_color.c | 31
>> ++++++++++++++++---------------
>>  1 file changed, 16 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_color.c
>> b/drivers/gpu/drm/i915/intel_color.c
>> index 333a23b..3b708a9 100644
>> --- a/drivers/gpu/drm/i915/intel_color.c
>> +++ b/drivers/gpu/drm/i915/intel_color.c
>> @@ -84,26 +84,27 @@ static bool crtc_state_is_legacy_gamma(struct
>> drm_crtc_state *state)
>>
>>  /*
>>   * When using limited range, multiply the matrix given by userspace
>> by
>> - * the matrix that we would use for the limited range. We do the
>> - * multiplication in U2.30 format.
>> + * the matrix that we would use for the limited range.
>>   */
>> -static void ctm_mult_by_limited(uint64_t *result, int64_t *input)
>> +static void ctm_mult_by_limited(u64 *result, const u64 *input)
>>  {
>>  	int i;
>>
>> -	for (i = 0; i < 9; i++)
>> -		result[i] = 0;
>> +	for (i = 0; i < 9; i++) {
>> +		u64 user_coeff = input[i];
>> +		uint32_t limited_coeff = CTM_COEFF_LIMITED_RANGE;
>
>You forgot s/uint32_t/u32/ here...

This file is using this extensively, have changed this function though. I guess it will
need a bigger cleanup.

>
>> +		uint32_t abs_coeff = clamp_val(
>
>and here. And aving a newline here seems weird.

Have updated this and re-sent a new patch.

Thanks & Regards,
Uma Shankar
>
>> +						CTM_COEFF_ABS(user_coeff),
>> +						0,
>> +						CTM_COEFF_4_0 - 1) >> 2;
>>
>> -	for (i = 0; i < 3; i++) {
>> -		int64_t user_coeff = input[i * 3 + i];
>> -		uint64_t limited_coeff = CTM_COEFF_LIMITED_RANGE >> 2;
>> -		uint64_t abs_coeff = clamp_val(CTM_COEFF_ABS(user_coeff),
>> -					       0,
>> -					       CTM_COEFF_4_0 - 1) >> 2;
>> -
>> -		result[i * 3 + i] = (limited_coeff * abs_coeff) >> 27;
>> -		if (CTM_COEFF_NEGATIVE(user_coeff))
>> -			result[i * 3 + i] |= CTM_COEFF_SIGN;
>> +		/*
>> +		 * By scaling every co-efficient with limited range (16-235)
>> +		 * vs full range (0-255) the final o/p will be scaled down to
>> +		 * fit in the limited range supported by the panel.
>> +		 */
>> +		result[i] = mul_u32_u32(limited_coeff, abs_coeff) >> 30;
>> +		result[i] |= user_coeff & CTM_COEFF_SIGN;
>>  	}
>>  }
>>
>> --
>> 1.9.1
>>
>> _______________________________________________
>> Intel-gfx mailing list
>> Intel-gfx at lists.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/intel-gfx
>
>--
>Ville Syrjälä
>Intel OTC