[PATCH] drm/stm: ltdc: add clut mode support

[Philippe CORNU]

+ Peter

Hi Peter,

CLUT support on STM32 has been removed thanks to your clean up patch 
named "drm: stm: remove dead code and pointless local lut storage" 
(https://patchwork.freedesktop.org/patch/166898/)

This below patch puts back the clut mode support using the new drm gamma 
api.

May I ask you please a short review on this patch?

Many thanks,
Philippe :-)


On 10/26/2017 01:17 PM, Philippe Cornu wrote:
> Add the 8-bit clut mode support at crtc level.
> Useful for low memory footprint user interfaces but also for
> 8-bit old games (including color shifting visual effects).
> Tested with fbdev FBIOPUTCMAP & drm DRM_IOCTL_MODE_SETGAMMA
> ioctls.
> 
> Signed-off-by: Philippe Cornu <philippe.cornu at st.com>
> ---
>   drivers/gpu/drm/stm/ltdc.c | 30 ++++++++++++++++++++++++++++++
>   1 file changed, 30 insertions(+)
> 
> diff --git a/drivers/gpu/drm/stm/ltdc.c b/drivers/gpu/drm/stm/ltdc.c
> index 7be6710..d5c8a42 100644
> --- a/drivers/gpu/drm/stm/ltdc.c
> +++ b/drivers/gpu/drm/stm/ltdc.c
> @@ -174,6 +174,8 @@
>   
>   #define LXCFBLNR_CFBLN	GENMASK(10, 0)	/* Color Frame Buffer Line Number */
>   
> +#define CLUT_SIZE	256
> +
>   #define CONSTA_MAX	0xFF		/* CONSTant Alpha MAX= 1.0 */
>   #define BF1_PAXCA	0x600		/* Pixel Alpha x Constant Alpha */
>   #define BF1_CA		0x400		/* Constant Alpha */
> @@ -362,6 +364,28 @@ static irqreturn_t ltdc_irq(int irq, void *arg)
>    * DRM_CRTC
>    */
>   
> +static void ltdc_crtc_update_clut(struct drm_crtc *crtc)
> +{
> +	struct ltdc_device *ldev = crtc_to_ltdc(crtc);
> +	struct drm_color_lut *lut;
> +	u32 val;
> +	int i;
> +
> +	if (!crtc || !crtc->state)
> +		return;
> +
> +	if (!crtc->state->color_mgmt_changed || !crtc->state->gamma_lut)
> +		return;
> +
> +	lut = (struct drm_color_lut *)crtc->state->gamma_lut->data;
> +
> +	for (i = 0; i < CLUT_SIZE; i++, lut++) {
> +		val = ((lut->red << 8) & 0xff0000) | (lut->green & 0xff00) |
> +			(lut->blue >> 8) | (i << 24);
> +		reg_write(ldev->regs, LTDC_L1CLUTWR, val);
> +	}
> +}
> +
>   static void ltdc_crtc_atomic_enable(struct drm_crtc *crtc,
>   				    struct drm_crtc_state *old_state)
>   {
> @@ -485,6 +509,8 @@ static void ltdc_crtc_atomic_flush(struct drm_crtc *crtc,
>   
>   	DRM_DEBUG_ATOMIC("\n");
>   
> +	ltdc_crtc_update_clut(crtc);
> +
>   	/* Commit shadow registers = update planes at next vblank */
>   	reg_set(ldev->regs, LTDC_SRCR, SRCR_VBR);
>   
> @@ -532,6 +558,7 @@ void ltdc_crtc_disable_vblank(struct drm_device *ddev, unsigned int pipe)
>   	.reset = drm_atomic_helper_crtc_reset,
>   	.atomic_duplicate_state = drm_atomic_helper_crtc_duplicate_state,
>   	.atomic_destroy_state = drm_atomic_helper_crtc_destroy_state,
> +	.gamma_set = drm_atomic_helper_legacy_gamma_set,
>   };
>   
>   /*
> @@ -764,6 +791,9 @@ static int ltdc_crtc_init(struct drm_device *ddev, struct drm_crtc *crtc)
>   
>   	drm_crtc_helper_add(crtc, &ltdc_crtc_helper_funcs);
>   
> +	drm_mode_crtc_set_gamma_size(crtc, CLUT_SIZE);
> +	drm_crtc_enable_color_mgmt(crtc, 0, false, CLUT_SIZE);
> +
>   	DRM_DEBUG_DRIVER("CRTC:%d created\n", crtc->base.id);
>   
>   	/* Add planes. Note : the first layer is used by primary plane */
>