drm/mgag200: Use helpers for programming gamma ramps

Replace mgag200's code for programming the hardware gamma LUT with
DRM helpers. Either load a provided gamma ramp or program a default.
Set the individual entries with a callback.

Each gamma value is given as 3 individual 16-bit values for red,
green and blue. The driver reduces them to 8 bit to make them fit
into hardware registers.

v2:
- fix coding style

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Jocelyn Falempe <jfalempe@redhat.com>
Link: https://lore.kernel.org/r/20250520094203.30545-4-tzimmermann@suse.de

5 files changed, 44 insertions, 58 deletions

diff --git a/drivers/gpu/drm/mgag200/mgag200_drv.h b/drivers/gpu/drm/mgag200/mgag200_drv.h
index 819a7e9381e3..f4bf40cd7c88 100644
--- a/drivers/gpu/drm/mgag200/mgag200_drv.h
+++ b/drivers/gpu/drm/mgag200/mgag200_drv.h
@@ -382,10 +382,10 @@ int mgag200_primary_plane_helper_get_scanout_buffer(struct drm_plane *plane,
 	.destroy = drm_plane_cleanup, \
 	DRM_GEM_SHADOW_PLANE_FUNCS
 
-void mgag200_crtc_set_gamma_linear(struct mga_device *mdev, const struct drm_format_info *format);
-void mgag200_crtc_set_gamma(struct mga_device *mdev,
-			    const struct drm_format_info *format,
-			    struct drm_color_lut *lut);
+void mgag200_crtc_fill_gamma(struct mga_device *mdev, const struct drm_format_info *format);
+void mgag200_crtc_load_gamma(struct mga_device *mdev,
+			     const struct drm_format_info *format,
+			     struct drm_color_lut *lut);
 
 enum drm_mode_status mgag200_crtc_helper_mode_valid(struct drm_crtc *crtc,
 						    const struct drm_display_mode *mode);
diff --git a/drivers/gpu/drm/mgag200/mgag200_g200er.c b/drivers/gpu/drm/mgag200/mgag200_g200er.c
index c20ed0ab50ec..23debc70dc54 100644
--- a/drivers/gpu/drm/mgag200/mgag200_g200er.c
+++ b/drivers/gpu/drm/mgag200/mgag200_g200er.c
@@ -200,9 +200,9 @@ static void mgag200_g200er_crtc_helper_atomic_enable(struct drm_crtc *crtc,
 	mgag200_g200er_reset_tagfifo(mdev);
 
 	if (crtc_state->gamma_lut)
-		mgag200_crtc_set_gamma(mdev, format, crtc_state->gamma_lut->data);
+		mgag200_crtc_load_gamma(mdev, format, crtc_state->gamma_lut->data);
 	else
-		mgag200_crtc_set_gamma_linear(mdev, format);
+		mgag200_crtc_fill_gamma(mdev, format);
 
 	mgag200_enable_display(mdev);
 }
diff --git a/drivers/gpu/drm/mgag200/mgag200_g200ev.c b/drivers/gpu/drm/mgag200/mgag200_g200ev.c
index 78be964eb97c..f8796e2b7a0f 100644
--- a/drivers/gpu/drm/mgag200/mgag200_g200ev.c
+++ b/drivers/gpu/drm/mgag200/mgag200_g200ev.c
@@ -201,9 +201,9 @@ static void mgag200_g200ev_crtc_helper_atomic_enable(struct drm_crtc *crtc,
 	mgag200_g200ev_set_hiprilvl(mdev);
 
 	if (crtc_state->gamma_lut)
-		mgag200_crtc_set_gamma(mdev, format, crtc_state->gamma_lut->data);
+		mgag200_crtc_load_gamma(mdev, format, crtc_state->gamma_lut->data);
 	else
-		mgag200_crtc_set_gamma_linear(mdev, format);
+		mgag200_crtc_fill_gamma(mdev, format);
 
 	mgag200_enable_display(mdev);
 }
diff --git a/drivers/gpu/drm/mgag200/mgag200_g200se.c b/drivers/gpu/drm/mgag200/mgag200_g200se.c
index 7a32d3b1d226..e80da12ba1fe 100644
--- a/drivers/gpu/drm/mgag200/mgag200_g200se.c
+++ b/drivers/gpu/drm/mgag200/mgag200_g200se.c
@@ -332,9 +332,9 @@ static void mgag200_g200se_crtc_helper_atomic_enable(struct drm_crtc *crtc,
 	mgag200_g200se_set_hiprilvl(mdev, adjusted_mode, format);
 
 	if (crtc_state->gamma_lut)
-		mgag200_crtc_set_gamma(mdev, format, crtc_state->gamma_lut->data);
+		mgag200_crtc_load_gamma(mdev, format, crtc_state->gamma_lut->data);
 	else
-		mgag200_crtc_set_gamma_linear(mdev, format);
+		mgag200_crtc_fill_gamma(mdev, format);
 
 	mgag200_enable_display(mdev);
 }
diff --git a/drivers/gpu/drm/mgag200/mgag200_mode.c b/drivers/gpu/drm/mgag200/mgag200_mode.c
index 6067d08aeee3..951d715dea30 100644
--- a/drivers/gpu/drm/mgag200/mgag200_mode.c
+++ b/drivers/gpu/drm/mgag200/mgag200_mode.c
@@ -13,6 +13,7 @@
 
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
+#include <drm/drm_color_mgmt.h>
 #include <drm/drm_damage_helper.h>
 #include <drm/drm_edid.h>
 #include <drm/drm_format_helper.h>
@@ -30,35 +31,37 @@
  * This file contains setup code for the CRTC.
  */
 
-void mgag200_crtc_set_gamma_linear(struct mga_device *mdev,
-				   const struct drm_format_info *format)
+static void mgag200_set_gamma_lut(struct drm_crtc *crtc, unsigned int index,
+				  u16 red, u16 green, u16 blue)
 {
-	int i;
+	struct drm_device *dev = crtc->dev;
+	struct mga_device *mdev = to_mga_device(dev);
+	u8 i8 = index & 0xff;
+	u8 r8 = red >> 8;
+	u8 g8 = green >> 8;
+	u8 b8 = blue >> 8;
+
+	if (drm_WARN_ON_ONCE(dev, index != i8))
+		return; /* driver bug */
+
+	WREG8(DAC_INDEX + MGA1064_INDEX, i8);
+	WREG8(DAC_INDEX + MGA1064_COL_PAL, r8);
+	WREG8(DAC_INDEX + MGA1064_COL_PAL, g8);
+	WREG8(DAC_INDEX + MGA1064_COL_PAL, b8);
+}
 
-	WREG8(DAC_INDEX + MGA1064_INDEX, 0);
+void mgag200_crtc_fill_gamma(struct mga_device *mdev,
+			     const struct drm_format_info *format)
+{
+	struct drm_crtc *crtc = &mdev->crtc;
 
 	switch (format->format) {
 	case DRM_FORMAT_RGB565:
-		/* Use better interpolation, to take 32 values from 0 to 255 */
-		for (i = 0; i < MGAG200_LUT_SIZE / 8; i++) {
-			WREG8(DAC_INDEX + MGA1064_COL_PAL, i * 8 + i / 4);
-			WREG8(DAC_INDEX + MGA1064_COL_PAL, i * 4 + i / 16);
-			WREG8(DAC_INDEX + MGA1064_COL_PAL, i * 8 + i / 4);
-		}
-		/* Green has one more bit, so add padding with 0 for red and blue. */
-		for (i = MGAG200_LUT_SIZE / 8; i < MGAG200_LUT_SIZE / 4; i++) {
-			WREG8(DAC_INDEX + MGA1064_COL_PAL, 0);
-			WREG8(DAC_INDEX + MGA1064_COL_PAL, i * 4 + i / 16);
-			WREG8(DAC_INDEX + MGA1064_COL_PAL, 0);
-		}
+		drm_crtc_fill_gamma_565(crtc, mgag200_set_gamma_lut);
 		break;
 	case DRM_FORMAT_RGB888:
 	case DRM_FORMAT_XRGB8888:
-		for (i = 0; i < MGAG200_LUT_SIZE; i++) {
-			WREG8(DAC_INDEX + MGA1064_COL_PAL, i);
-			WREG8(DAC_INDEX + MGA1064_COL_PAL, i);
-			WREG8(DAC_INDEX + MGA1064_COL_PAL, i);
-		}
+		drm_crtc_fill_gamma_888(crtc, mgag200_set_gamma_lut);
 		break;
 	default:
 		drm_warn_once(&mdev->base, "Unsupported format %p4cc for gamma correction\n",
@@ -67,36 +70,19 @@ void mgag200_crtc_set_gamma_linear(struct mga_device *mdev,
 	}
 }
 
-void mgag200_crtc_set_gamma(struct mga_device *mdev,
-			    const struct drm_format_info *format,
-			    struct drm_color_lut *lut)
+void mgag200_crtc_load_gamma(struct mga_device *mdev,
+			     const struct drm_format_info *format,
+			     struct drm_color_lut *lut)
 {
-	int i;
-
-	WREG8(DAC_INDEX + MGA1064_INDEX, 0);
+	struct drm_crtc *crtc = &mdev->crtc;
 
 	switch (format->format) {
 	case DRM_FORMAT_RGB565:
-		/* Use better interpolation, to take 32 values from lut[0] to lut[255] */
-		for (i = 0; i < MGAG200_LUT_SIZE / 8; i++) {
-			WREG8(DAC_INDEX + MGA1064_COL_PAL, lut[i * 8 + i / 4].red >> 8);
-			WREG8(DAC_INDEX + MGA1064_COL_PAL, lut[i * 4 + i / 16].green >> 8);
-			WREG8(DAC_INDEX + MGA1064_COL_PAL, lut[i * 8 + i / 4].blue >> 8);
-		}
-		/* Green has one more bit, so add padding with 0 for red and blue. */
-		for (i = MGAG200_LUT_SIZE / 8; i < MGAG200_LUT_SIZE / 4; i++) {
-			WREG8(DAC_INDEX + MGA1064_COL_PAL, 0);
-			WREG8(DAC_INDEX + MGA1064_COL_PAL, lut[i * 4 + i / 16].green >> 8);
-			WREG8(DAC_INDEX + MGA1064_COL_PAL, 0);
-		}
+		drm_crtc_load_gamma_565_from_888(crtc, lut, mgag200_set_gamma_lut);
 		break;
 	case DRM_FORMAT_RGB888:
 	case DRM_FORMAT_XRGB8888:
-		for (i = 0; i < MGAG200_LUT_SIZE; i++) {
-			WREG8(DAC_INDEX + MGA1064_COL_PAL, lut[i].red >> 8);
-			WREG8(DAC_INDEX + MGA1064_COL_PAL, lut[i].green >> 8);
-			WREG8(DAC_INDEX + MGA1064_COL_PAL, lut[i].blue >> 8);
-		}
+		drm_crtc_load_gamma_888(crtc, lut, mgag200_set_gamma_lut);
 		break;
 	default:
 		drm_warn_once(&mdev->base, "Unsupported format %p4cc for gamma correction\n",
@@ -642,9 +628,9 @@ void mgag200_crtc_helper_atomic_flush(struct drm_crtc *crtc, struct drm_atomic_s
 		const struct drm_format_info *format = mgag200_crtc_state->format;
 
 		if (crtc_state->gamma_lut)
-			mgag200_crtc_set_gamma(mdev, format, crtc_state->gamma_lut->data);
+			mgag200_crtc_load_gamma(mdev, format, crtc_state->gamma_lut->data);
 		else
-			mgag200_crtc_set_gamma_linear(mdev, format);
+			mgag200_crtc_fill_gamma(mdev, format);
 	}
 }
 
@@ -665,9 +651,9 @@ void mgag200_crtc_helper_atomic_enable(struct drm_crtc *crtc, struct drm_atomic_
 		funcs->pixpllc_atomic_update(crtc, old_state);
 
 	if (crtc_state->gamma_lut)
-		mgag200_crtc_set_gamma(mdev, format, crtc_state->gamma_lut->data);
+		mgag200_crtc_load_gamma(mdev, format, crtc_state->gamma_lut->data);
 	else
-		mgag200_crtc_set_gamma_linear(mdev, format);
+		mgag200_crtc_fill_gamma(mdev, format);
 
 	mgag200_enable_display(mdev);
 }