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Subject[PATCH] drm/stm: ltdc: add clut mode support
Date
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@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 */
--
1.9.1
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