Re: [v9][PATCH 03/11] drm/i915/display: Add func to compare hw/sw gamma lut

From: "Sharma, Swati2" <swati2.sharma@intel.com>
To: Jani Nikula <jani.nikula@intel.com>, intel-gfx@lists.freedesktop.org
Cc: daniel.vetter@ffwll.ch, ankit.k.nautiyal@intel.com
Subject: Re: [v9][PATCH 03/11] drm/i915/display: Add func to compare hw/sw gamma lut
Date: Mon, 9 Sep 2019 19:23:53 +0530	[thread overview]
Message-ID: <4ac855fd-0a05-db42-28b8-ed1c65b2428a@intel.com> (raw)
In-Reply-To: <87o9066cr1.fsf@intel.com>

On 30-Aug-19 6:17 PM, Jani Nikula wrote:
> On Fri, 30 Aug 2019, Swati Sharma <swati2.sharma@intel.com> wrote:
>> Add func intel_color_lut_equal() to compare hw/sw gamma
>> lut values. Since hw/sw gamma lut sizes and lut entries comparison
>> will be different for different gamma modes, add gamma mode dependent
>> checks.
>>
>> v3: -Rebase
>> v4: -Renamed intel_compare_color_lut() to intel_color_lut_equal() [Jani]
>>      -Added the default label above the correct label [Jani]
>>      -Corrected smatch warn "variable dereferenced before check"
>>       [Dan Carpenter]
>> v5: -Added condition (!blob1 && !blob2) return true [Jani]
>> v6: -Made patch11 as patch3 [Jani]
>> v8: -Split patch 3 into 4 patches
>>      -Optimized blob check condition [Ville]
>> v9: -Exclude spilt gamma mode (bdw and ivb platforms)
>>       as there is exception in way gamma values are written in
>>       hardware [Ville]
>>      -Added exception made in commit [Uma]
>>      -Dropeed else, character limit and indentation [Uma]
>>      -Added multi segmented gama mode for icl+ platforms [Uma]
>>
>> Signed-off-by: Swati Sharma <swati2.sharma@intel.com>
>> ---
>>   drivers/gpu/drm/i915/display/intel_color.c | 104 +++++++++++++++++++++++++++++
>>   drivers/gpu/drm/i915/display/intel_color.h |   6 ++
>>   2 files changed, 110 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/display/intel_color.c b/drivers/gpu/drm/i915/display/intel_color.c
>> index dcc65d7..141efb0 100644
>> --- a/drivers/gpu/drm/i915/display/intel_color.c
>> +++ b/drivers/gpu/drm/i915/display/intel_color.c
>> @@ -1470,6 +1470,110 @@ int intel_color_get_gamma_bit_precision(const struct intel_crtc_state *crtc_stat
>>   	return 0;
>>   }
>>   
>> +static inline bool err_check(struct drm_color_lut *sw_lut,
> 
> Please drop the inline throughout in .c files. For static functions the
> compiler will make the best call what to do here.
> 
>> +			     struct drm_color_lut *hw_lut, u32 err)
>> +{
>> +	return ((abs((long)hw_lut->red - sw_lut->red)) <= err) &&
>> +		((abs((long)hw_lut->blue - sw_lut->blue)) <= err) &&
>> +		((abs((long)hw_lut->green - sw_lut->green)) <= err);
>> +}
>> +
>> +static inline bool intel_color_lut_entry_equal(struct drm_color_lut *sw_lut,
>> +					       struct drm_color_lut *hw_lut,
>> +					       int hw_lut_size, u32 err)
>> +{
>> +	int i;
>> +
>> +	for (i = 0; i < hw_lut_size; i++) {
>> +		if (!err_check(&hw_lut[i], &sw_lut[i], err))
>> +			return false;
>> +	}
>> +
>> +	return true;
>> +}
>> +
>> +static inline bool intel_color_lut_entry_equal_multi(struct drm_color_lut *sw_lut,
>> +						     struct drm_color_lut *hw_lut,
>> +						     u32 err)
>> +{
>> +	int i;
>> +
>> +	for (i = 0; i < 9; i++) {
>> +		if (!err_check(&hw_lut[i], &sw_lut[i], err))
>> +			return false;
>> +	}
>> +
>> +	for (i = 1; i <  257; i++) {
>> +		if (!err_check(&hw_lut[8 + i], &sw_lut[i * 8], err))
>> +			return false;
>> +	}
>> +
>> +	for (i = 0; i < 256; i++) {
>> +		if (!err_check(&hw_lut[265 + i], &sw_lut[i * 8 * 128], err))
>> +			return false;
>> +	}
>> +
>> +	return true;
>> +}
>> +
>> +bool intel_color_lut_equal(struct drm_property_blob *blob1,
>> +			   struct drm_property_blob *blob2,
>> +			   u32 gamma_mode, u32 bit_precision)
>> +{
>> +	struct drm_color_lut *sw_lut, *hw_lut;
>> +	int sw_lut_size, hw_lut_size;
>> +	u32 err;
>> +
>> +	if (!blob1 != !blob2)
>> +		return false;
>> +
>> +	if (!blob1)
>> +		return true;
>> +
>> +	sw_lut_size = drm_color_lut_size(blob1);
>> +	hw_lut_size = drm_color_lut_size(blob2);
> 
> Basically the code here shouldn't assume one is hw state and the other
> is sw state...
> 
>> +
>> +	/* check sw and hw lut size */
>> +	switch (gamma_mode) {
>> +	case GAMMA_MODE_MODE_8BIT:
>> +	case GAMMA_MODE_MODE_10BIT:
>> +		if (sw_lut_size != hw_lut_size)
>> +			return false;
>> +		break;
>> +	case GAMMA_MODE_MODE_12BIT_MULTI_SEGMENTED:
>> +		if ((sw_lut_size != 262145) || (hw_lut_size != 521))
>> +			return false;
> 
> The readout code should result in a blob similar to the hardware
> state. Assuming distinct hw and sw, you'll bypass fastset on icl
> whenever multisegmented gamma is enabled! See
> intel_crtc_check_fastset().
> 
> Ville also pointed out that on fastboot, the state read out from the
> hardware is presented to the userspace, resulting in a bogus 521 lut
> size.
> 
> So the readout code for multisegmented gamma has to come up with some
> intermediate entries that aren't preserved in hardware. Not unlike the
> precision is lost in hardware. Those may be read out by the userspace
> after fastboot. The compare code has to ignore those interpolated
> values, and only look at the values that have been read from the
> hardware.
> 
Hi Jani,
As you stated readout code should result in a blob similar to hardware
state and readout code for multi-seg gamma has to come up with 
"intermediate values". Do these intermediate values need to be some
logical values or any junk values while creating a hw blob?

> This means intel_color_lut_entry_equal_multi() as-is does not fly.
> 
> ---
> 
> More importantly, this also means the patch can't be merged, and what
> could have been straightforward stuff for earlier gens and legacy gamma
> keeps being blocked by the more complicated stuff. So despite what I
> said in private, I'm afraid the best course of action is indeed to
> refactor the series to not include multi-segmented gamma, save it for a
> follow-up series.
> 
> For example, do the absolute minimal series to add GMCH platform gamma
> checks. Could even be without CHV for starters. Add the infrastructure,
> get it working, get it off our hands. After that, focus on the next.
> 
> BR,
> Jani.
> 
> 
>> +		break;
>> +	default:
>> +		MISSING_CASE(gamma_mode);
>> +			return false;
>> +	}
>> +
>> +	sw_lut = blob1->data;
>> +	hw_lut = blob2->data;
>> +
>> +	err = 0xffff >> bit_precision;
>> +
>> +	/* check sw and hw lut entry to be equal */
>> +	switch (gamma_mode) {
>> +	case GAMMA_MODE_MODE_8BIT:
>> +	case GAMMA_MODE_MODE_10BIT:
>> +		if (!intel_color_lut_entry_equal(sw_lut, hw_lut,
>> +						 hw_lut_size, err))
>> +			return false;
>> +		break;
>> +	case GAMMA_MODE_MODE_12BIT_MULTI_SEGMENTED:
>> +		if (!intel_color_lut_entry_equal_multi(sw_lut, hw_lut, err))
>> +			return false;
>> +		break;
>> +	default:
>> +		MISSING_CASE(gamma_mode);
>> +			return false;
>> +	}
>> +
>> +	return true;
>> +}
>> +
>>   void intel_color_init(struct intel_crtc *crtc)
>>   {
>>   	struct drm_i915_private *dev_priv = to_i915(crtc->base.dev);
>> diff --git a/drivers/gpu/drm/i915/display/intel_color.h b/drivers/gpu/drm/i915/display/intel_color.h
>> index 0226d3a..173727a 100644
>> --- a/drivers/gpu/drm/i915/display/intel_color.h
>> +++ b/drivers/gpu/drm/i915/display/intel_color.h
>> @@ -6,8 +6,11 @@
>>   #ifndef __INTEL_COLOR_H__
>>   #define __INTEL_COLOR_H__
>>   
>> +#include <linux/types.h>
>> +
>>   struct intel_crtc_state;
>>   struct intel_crtc;
>> +struct drm_property_blob;
>>   
>>   void intel_color_init(struct intel_crtc *crtc);
>>   int intel_color_check(struct intel_crtc_state *crtc_state);
>> @@ -15,5 +18,8 @@
>>   void intel_color_load_luts(const struct intel_crtc_state *crtc_state);
>>   void intel_color_get_config(struct intel_crtc_state *crtc_state);
>>   int intel_color_get_gamma_bit_precision(const struct intel_crtc_state *crtc_state);
>> +bool intel_color_lut_equal(struct drm_property_blob *blob1,
>> +			   struct drm_property_blob *blob2,
>> +			   u32 gamma_mode, u32 bit_precision);
>>   
>>   #endif /* __INTEL_COLOR_H__ */
> 


-- 
~Swati Sharma
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