Re: [Intel-gfx] [PATCH 11/11] drm/i915: Create resized LUTs for ivb+ split gamma mode

["Nautiyal, Ankit K" <ankit.k.nautiyal@intel.com>]

On 11/4/2022 3:12 PM, Ville Syrjälä wrote:
> On Fri, Nov 04, 2022 at 10:49:39AM +0530, Nautiyal, Ankit K wrote:
>> Patch looks good to me.
>>
>> Minor suggestions inline:
>>
>> On 10/26/2022 5:09 PM, Ville Syrjala wrote:
>>> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>>>
>>> Currently when opeating in split gamma mode we do the
>> nitpick: 'operating' typo.
>>> "skip ever other sw LUT entry" trick in the low level
>>> LUT programming/readout functions. That is very annoying
>>> and a big hinderance to revamping the color management
>>> uapi.
>>>
>>> Let's get rid of that problem by making half sized copies
>>> of the software LUTs and plugging those into the internal
>>> {pre,post}_csc_lut attachment points (instead of the sticking
>>> the uapi provide sw LUTs there directly).
>>>
>>> With this the low level stuff will operate purely in terms
>>> the hardware LUT sizes, and all uapi nonsense is contained
>>> to the atomic check phase. The one thing we do lose is
>>> intel_color_assert_luts() since we no longer have a way to
>>> check that the uapi LUTs were correctly used when generating
>>> the internal copies. But that seems like a price worth paying.
>>>
>>> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
>>> ---
>>>    drivers/gpu/drm/i915/display/intel_color.c | 81 +++++++++++++++++-----
>>>    1 file changed, 64 insertions(+), 17 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/i915/display/intel_color.c b/drivers/gpu/drm/i915/display/intel_color.c
>>> index 33871bfacee7..d48904f90e3a 100644
>>> --- a/drivers/gpu/drm/i915/display/intel_color.c
>>> +++ b/drivers/gpu/drm/i915/display/intel_color.c
>>> @@ -597,6 +597,30 @@ create_linear_lut(struct drm_i915_private *i915, int lut_size)
>>>    	return blob;
>>>    }
>>>    
>>> +static struct drm_property_blob *
>>> +create_resized_lut(struct drm_i915_private *i915,
>>> +		   const struct drm_property_blob *blob_in, int lut_out_size)
>>> +{
>>> +	int i, lut_in_size = drm_color_lut_size(blob_in);
>>> +	struct drm_property_blob *blob_out;
>>> +	const struct drm_color_lut *lut_in;
>>> +	struct drm_color_lut *lut_out;
>>> +
>>> +	blob_out = drm_property_create_blob(&i915->drm,
>>> +					    sizeof(lut_out[0]) * lut_out_size,
>>> +					    NULL);
>>> +	if (IS_ERR(blob_out))
>>> +		return blob_out;
>>> +
>>> +	lut_in = blob_in->data;
>>> +	lut_out = blob_out->data;
>>> +
>>> +	for (i = 0; i < lut_out_size; i++)
>>> +		lut_out[i] = lut_in[i * (lut_in_size - 1) / (lut_out_size - 1)];
>>> +
>>> +	return blob_out;
>>> +}
>>> +
>>>    static void i9xx_load_lut_8(struct intel_crtc *crtc,
>>>    			    const struct drm_property_blob *blob)
>>>    {
>>> @@ -723,19 +747,14 @@ static void ivb_load_lut_10(struct intel_crtc *crtc,
>>>    			    u32 prec_index)
>>>    {
>>>    	struct drm_i915_private *i915 = to_i915(crtc->base.dev);
>>> -	int hw_lut_size = ivb_lut_10_size(prec_index);
>>>    	const struct drm_color_lut *lut = blob->data;
>>>    	int i, lut_size = drm_color_lut_size(blob);
>>>    	enum pipe pipe = crtc->pipe;
>>>    
>>> -	for (i = 0; i < hw_lut_size; i++) {
>>> -		/* We discard half the user entries in split gamma mode */
>>> -		const struct drm_color_lut *entry =
>>> -			&lut[i * (lut_size - 1) / (hw_lut_size - 1)];
>>> -
>>> +	for (i = 0; i < lut_size; i++) {
>>>    		intel_de_write_fw(i915, PREC_PAL_INDEX(pipe), prec_index++);
>>>    		intel_de_write_fw(i915, PREC_PAL_DATA(pipe),
>>> -				  ilk_lut_10(entry));
>>> +				  ilk_lut_10(&lut[i]));
>>>    	}
>>>    
>>>    	/*
>>> @@ -751,7 +770,6 @@ static void bdw_load_lut_10(struct intel_crtc *crtc,
>>>    			    u32 prec_index)
>>>    {
>>>    	struct drm_i915_private *i915 = to_i915(crtc->base.dev);
>>> -	int hw_lut_size = ivb_lut_10_size(prec_index);
>>>    	const struct drm_color_lut *lut = blob->data;
>>>    	int i, lut_size = drm_color_lut_size(blob);
>>>    	enum pipe pipe = crtc->pipe;
>>> @@ -759,14 +777,9 @@ static void bdw_load_lut_10(struct intel_crtc *crtc,
>>>    	intel_de_write_fw(i915, PREC_PAL_INDEX(pipe),
>>>    			  prec_index | PAL_PREC_AUTO_INCREMENT);
>>>    
>>> -	for (i = 0; i < hw_lut_size; i++) {
>>> -		/* We discard half the user entries in split gamma mode */
>>> -		const struct drm_color_lut *entry =
>>> -			&lut[i * (lut_size - 1) / (hw_lut_size - 1)];
>>> -
>>> +	for (i = 0; i < lut_size; i++)
>>>    		intel_de_write_fw(i915, PREC_PAL_DATA(pipe),
>>> -				  ilk_lut_10(entry));
>>> -	}
>>> +				  ilk_lut_10(&lut[i]));
>>>    
>>>    	/*
>>>    	 * Reset the index, otherwise it prevents the legacy palette to be
>>> @@ -1343,7 +1356,7 @@ void intel_color_assert_luts(const struct intel_crtc_state *crtc_state)
>>>    			    crtc_state->pre_csc_lut != i915->display.color.glk_linear_degamma_lut);
>>>    		drm_WARN_ON(&i915->drm,
>>>    			    crtc_state->post_csc_lut != crtc_state->hw.gamma_lut);
>>> -	} else {
>>> +	} else if (crtc_state->gamma_mode != GAMMA_MODE_MODE_SPLIT) {
>>>    		drm_WARN_ON(&i915->drm,
>>>    			    crtc_state->pre_csc_lut != crtc_state->hw.degamma_lut &&
>>>    			    crtc_state->pre_csc_lut != crtc_state->hw.gamma_lut);
>>> @@ -1564,6 +1577,38 @@ static u32 ivb_csc_mode(const struct intel_crtc_state *crtc_state)
>>>    	return CSC_POSITION_BEFORE_GAMMA;
>>>    }
>>>    
>>> +static int ivb_assign_luts(struct intel_crtc_state *crtc_state)
>>> +{
>>> +	struct drm_i915_private *i915 = to_i915(crtc_state->uapi.crtc->dev);
>>> +	struct drm_property_blob *degamma_lut, *gamma_lut;
>>> +
>>> +	if (crtc_state->gamma_mode != GAMMA_MODE_MODE_SPLIT) {
>>> +		ilk_assign_luts(crtc_state);
>>> +		return 0;
>>> +	}
>>> +
>>> +	drm_WARN_ON(&i915->drm, drm_color_lut_size(crtc_state->hw.degamma_lut) != 1024);
>>> +	drm_WARN_ON(&i915->drm, drm_color_lut_size(crtc_state->hw.gamma_lut) != 1024);
>> Does it make sense to use some macro for LUT size for split gamma case
>> and regular case?
>>
>> Same thing perhaps can be used in ivb_lut_10_size?
> I don't think macros would be really helpful. I guess I
> could have used ivb_lut_10_size() for the create_resized_lut()
> calls below. And these WARNs I guess could have just used
> device info stuff instead.

Using ivb_lut_10_size() should be good enough, I think.

In any case, this is a just a minor suggestion. Patch looks good to me.

With the small typo fixed in commit message:

Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>


Regards,

Ankit


> Or I could just drop them entirely
> since they aren't really checking anything super important, and
> the create_resized_lut() would work with any input LUT size anyway.
>
> Thinking a bit further we could certainly consider extending
> the ivb_lut_10_size()/glk_degamma_lut_size() approach to cover
> all the gamma modes. Though I think it would probably make sense
> to implement that as some kind of struct based approach where we
> describe each LUT format in a struct. Would also be more in line
> with what we've been thinking for the uapi revamp.
>