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

[Peter Rosin]

On 2017-11-07 16:53, Philippe CORNU wrote:
> + Peter
> 
> Hi Peter,
> 
> CLUT support on STM32 has been removed thanks to your clean up patch 

Support is a bit strong for what I thought was a dead function, or
are you saying that it used to work before my series? Really sorry
if that is the case!

Anyway, the function I removed seemed to indicate that the hardware
could handle a separate clut for each layer, but your new version
does not. Why is that?

Cheers,
peda

> 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 */