Re: [PATCH v1, 1/1] drm/mediatek: add lut diff flag for new gamma hardware support

[CK Hu]

Hi, Yongqiang:

On Wed, 2022-04-20 at 21:06 +0800, Yongqiang Niu wrote:
> From: Yongqiang Niu <yongqiang.niu@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
> 
> mt8183 gamma module usage is different with before soc,
> gamma odd(index start from 0) lut value set to hardware
> register should be
> the difference of current lut value with last lut value.
> 
> gamma function support both increase and decrease lut.

How to set decrease lut?

Original lut:
12 10 8 6 4 2

Does diff lut look like this?
12 [2] 8 [2] 4 [2]

How does hardware know that this is increase lut or decrease lut?

> chrome os app set increase lut normally.
> 
> for increase lut example, chrome os user space set lut
> like this(only r chanel for example):
> 2 4 6 8 10 12.
> 1) mt8183 gamma driver should set the gamma lut to hardware
> register like this:
> 2 [2] 6 [8] 10 [2]

2 [2] 6 [2] 10 [2]

> the value with [] is the difference value
> 2) gamma hardware will restore the lut when apply gamma
> function to display

I don't know why do you mention the 'restore', any modification is
related to this?

> 
> Signed-off-by: Yongqiang Niu <
> yongqiang.niu@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx>
> ---
>  drivers/gpu/drm/mediatek/mtk_disp_aal.c   |  4 ++-
>  drivers/gpu/drm/mediatek/mtk_disp_drv.h   |  2 +-
>  drivers/gpu/drm/mediatek/mtk_disp_gamma.c | 34 +++++++++++++++++++
> ----
>  3 files changed, 32 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/gpu/drm/mediatek/mtk_disp_aal.c
> b/drivers/gpu/drm/mediatek/mtk_disp_aal.c
> index f46d4ab73d6a..e6378b074a17 100644
> --- a/drivers/gpu/drm/mediatek/mtk_disp_aal.c
> +++ b/drivers/gpu/drm/mediatek/mtk_disp_aal.c
> @@ -23,6 +23,7 @@
>  
>  struct mtk_disp_aal_data {
>  	bool has_gamma;
> +	bool lut_diff;
>  };
>  
>  /**
> @@ -66,7 +67,7 @@ void mtk_aal_gamma_set(struct device *dev, struct
> drm_crtc_state *state)
>  	struct mtk_disp_aal *aal = dev_get_drvdata(dev);
>  
>  	if (aal->data && aal->data->has_gamma)
> -		mtk_gamma_set_common(aal->regs, state);
> +		mtk_gamma_set_common(aal->regs, state, aal->data-
> >lut_diff);

gamma in aal does not support diff lut, so this would make things
simple.

mtk_gamma_set_common(aal->regs, state, false);

Regards,
CK

>  }
>  
>  void mtk_aal_start(struct device *dev)
> @@ -148,6 +149,7 @@ static int mtk_disp_aal_remove(struct
> platform_device *pdev)
>  
>  static const struct mtk_disp_aal_data mt8173_aal_driver_data = {
>  	.has_gamma = true,
> +	.lut_diff = false,
>  };
>  
>  static const struct of_device_id mtk_disp_aal_driver_dt_match[] = {
> diff --git a/drivers/gpu/drm/mediatek/mtk_disp_drv.h
> b/drivers/gpu/drm/mediatek/mtk_disp_drv.h
> index 86c3068894b1..3380651c6707 100644
> --- a/drivers/gpu/drm/mediatek/mtk_disp_drv.h
> +++ b/drivers/gpu/drm/mediatek/mtk_disp_drv.h
> @@ -51,7 +51,7 @@ void mtk_gamma_config(struct device *dev, unsigned
> int w,
>  		      unsigned int h, unsigned int vrefresh,
>  		      unsigned int bpc, struct cmdq_pkt *cmdq_pkt);
>  void mtk_gamma_set(struct device *dev, struct drm_crtc_state
> *state);
> -void mtk_gamma_set_common(void __iomem *regs, struct drm_crtc_state
> *state);
> +void mtk_gamma_set_common(void __iomem *regs, struct drm_crtc_state
> *state, bool lut_diff);
>  void mtk_gamma_start(struct device *dev);
>  void mtk_gamma_stop(struct device *dev);
>  
> diff --git a/drivers/gpu/drm/mediatek/mtk_disp_gamma.c
> b/drivers/gpu/drm/mediatek/mtk_disp_gamma.c
> index 3a5815ab4079..fec2e9a5b60d 100644
> --- a/drivers/gpu/drm/mediatek/mtk_disp_gamma.c
> +++ b/drivers/gpu/drm/mediatek/mtk_disp_gamma.c
> @@ -27,6 +27,7 @@
>  
>  struct mtk_disp_gamma_data {
>  	bool has_dither;
> +	bool lut_diff;
>  };
>  
>  /*
> @@ -53,12 +54,13 @@ void mtk_gamma_clk_disable(struct device *dev)
>  	clk_disable_unprepare(gamma->clk);
>  }
>  
> -void mtk_gamma_set_common(void __iomem *regs, struct drm_crtc_state
> *state)
> +void mtk_gamma_set_common(void __iomem *regs, struct drm_crtc_state
> *state, bool lut_diff)
>  {
>  	unsigned int i, reg;
>  	struct drm_color_lut *lut;
>  	void __iomem *lut_base;
>  	u32 word;
> +	u32 diff[3] = {0};
>  
>  	if (state->gamma_lut) {
>  		reg = readl(regs + DISP_GAMMA_CFG);
> @@ -67,9 +69,20 @@ void mtk_gamma_set_common(void __iomem *regs,
> struct drm_crtc_state *state)
>  		lut_base = regs + DISP_GAMMA_LUT;
>  		lut = (struct drm_color_lut *)state->gamma_lut->data;
>  		for (i = 0; i < MTK_LUT_SIZE; i++) {
> -			word = (((lut[i].red >> 6) & LUT_10BIT_MASK) <<
> 20) +
> -				(((lut[i].green >> 6) & LUT_10BIT_MASK)
> << 10) +
> -				((lut[i].blue >> 6) & LUT_10BIT_MASK);
> +
> +			if (!lut_diff || (i % 2 == 0)) {
> +				word = (((lut[i].red >> 6) &
> LUT_10BIT_MASK) << 20) +
> +					(((lut[i].green >> 6) &
> LUT_10BIT_MASK) << 10) +
> +					((lut[i].blue >> 6) &
> LUT_10BIT_MASK);
> +			} else {
> +				diff[0] = abs((lut[i].red >> 6) -
> (lut[i - 1].red >> 6));
> +				diff[1] = abs((lut[i].green >> 6) -
> (lut[i - 1].green >> 6));
> +				diff[2] = abs((lut[i].blue >> 6) -
> (lut[i - 1].blue >> 6));
> +
> +				word = ((diff[0] & LUT_10BIT_MASK) <<
> 20) +
> +					((diff[1] & LUT_10BIT_MASK) <<
> 10) +
> +					(diff[2] & LUT_10BIT_MASK);
> +			}
>  			writel(word, (lut_base + i * 4));
>  		}
>  	}
> @@ -78,8 +91,12 @@ void mtk_gamma_set_common(void __iomem *regs,
> struct drm_crtc_state *state)
>  void mtk_gamma_set(struct device *dev, struct drm_crtc_state *state)
>  {
>  	struct mtk_disp_gamma *gamma = dev_get_drvdata(dev);
> +	bool lut_diff = false;
> +
> +	if (gamma->data)
> +		lut_diff = gamma->data->lut_diff;
>  
> -	mtk_gamma_set_common(gamma->regs, state);
> +	mtk_gamma_set_common(gamma->regs, state, lut_diff);
>  }
>  
>  void mtk_gamma_config(struct device *dev, unsigned int w,
> @@ -176,10 +193,15 @@ static const struct mtk_disp_gamma_data
> mt8173_gamma_driver_data = {
>  	.has_dither = true,
>  };
>  
> +static const struct mtk_disp_gamma_data mt8183_gamma_driver_data = {
> +	.lut_diff = true,
> +};
> +
>  static const struct of_device_id mtk_disp_gamma_driver_dt_match[] =
> {
>  	{ .compatible = "mediatek,mt8173-disp-gamma",
>  	  .data = &mt8173_gamma_driver_data},
> -	{ .compatible = "mediatek,mt8183-disp-gamma"},
> +	{ .compatible = "mediatek,mt8183-disp-gamma",
> +	  .data = &mt8183_gamma_driver_data},
>  	{},
>  };
>  MODULE_DEVICE_TABLE(of, mtk_disp_gamma_driver_dt_match);