drm/ofdrm: Use helpers for programming gamma ramps

Replace ofdrm'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: Javier Martinez Canillas <javierm@redhat.com>
Link: https://lore.kernel.org/r/20250520094203.30545-5-tzimmermann@suse.de

diff --git a/drivers/gpu/drm/sysfb/ofdrm.c b/drivers/gpu/drm/sysfb/ofdrm.c
index fddfe8bea9f7f3d60cb412153c0b52a98c778a62..c9415f0cb3ed3ead08c6f7a233584a6158593096 100644 (file)
--- a/drivers/gpu/drm/sysfb/ofdrm.c
+++ b/drivers/gpu/drm/sysfb/ofdrm.c
@@ -8,6 +8,7 @@
 #include <drm/clients/drm_client_setup.h>
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_state_helper.h>
+#include <drm/drm_color_mgmt.h>
 #include <drm/drm_connector.h>
 #include <drm/drm_damage_helper.h>
 #include <drm/drm_device.h>
@@ -644,36 +645,36 @@ static void ofdrm_qemu_cmap_write(struct ofdrm_device *odev, unsigned char index
        writeb(b, data);
 }
 
-static void ofdrm_device_set_gamma_linear(struct ofdrm_device *odev,
-                                         const struct drm_format_info *format)
+static void ofdrm_set_gamma_lut(struct drm_crtc *crtc, unsigned int index,
+                               u16 red, u16 green, u16 blue)
+{
+       struct drm_device *dev = crtc->dev;
+       struct ofdrm_device *odev = ofdrm_device_of_dev(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 */
+
+       odev->funcs->cmap_write(odev, i8, r8, g8, b8);
+}
+
+static void ofdrm_device_fill_gamma(struct ofdrm_device *odev,
+                                   const struct drm_format_info *format)
 {
        struct drm_device *dev = &odev->sysfb.dev;
-       int i;
+       struct drm_crtc *crtc = &odev->crtc;
 
        switch (format->format) {
        case DRM_FORMAT_RGB565:
        case DRM_FORMAT_RGB565 | DRM_FORMAT_BIG_ENDIAN:
-               /* Use better interpolation, to take 32 values from 0 to 255 */
-               for (i = 0; i < OFDRM_GAMMA_LUT_SIZE / 8; i++) {
-                       unsigned char r = i * 8 + i / 4;
-                       unsigned char g = i * 4 + i / 16;
-                       unsigned char b = i * 8 + i / 4;
-
-                       odev->funcs->cmap_write(odev, i, r, g, b);
-               }
-               /* Green has one more bit, so add padding with 0 for red and blue. */
-               for (i = OFDRM_GAMMA_LUT_SIZE / 8; i < OFDRM_GAMMA_LUT_SIZE / 4; i++) {
-                       unsigned char r = 0;
-                       unsigned char g = i * 4 + i / 16;
-                       unsigned char b = 0;
-
-                       odev->funcs->cmap_write(odev, i, r, g, b);
-               }
+               drm_crtc_fill_gamma_565(crtc, ofdrm_set_gamma_lut);
                break;
        case DRM_FORMAT_XRGB8888:
        case DRM_FORMAT_BGRX8888:
-               for (i = 0; i < OFDRM_GAMMA_LUT_SIZE; i++)
-                       odev->funcs->cmap_write(odev, i, i, i, i);
+               drm_crtc_fill_gamma_888(crtc, ofdrm_set_gamma_lut);
                break;
        default:
                drm_warn_once(dev, "Unsupported format %p4cc for gamma correction\n",
@@ -682,42 +683,21 @@ static void ofdrm_device_set_gamma_linear(struct ofdrm_device *odev,
        }
 }
 
-static void ofdrm_device_set_gamma(struct ofdrm_device *odev,
-                                  const struct drm_format_info *format,
-                                  struct drm_color_lut *lut)
+static void ofdrm_device_load_gamma(struct ofdrm_device *odev,
+                                   const struct drm_format_info *format,
+                                   struct drm_color_lut *lut)
 {
        struct drm_device *dev = &odev->sysfb.dev;
-       int i;
+       struct drm_crtc *crtc = &odev->crtc;
 
        switch (format->format) {
        case DRM_FORMAT_RGB565:
        case DRM_FORMAT_RGB565 | DRM_FORMAT_BIG_ENDIAN:
-               /* Use better interpolation, to take 32 values from lut[0] to lut[255] */
-               for (i = 0; i < OFDRM_GAMMA_LUT_SIZE / 8; i++) {
-                       unsigned char r = lut[i * 8 + i / 4].red >> 8;
-                       unsigned char g = lut[i * 4 + i / 16].green >> 8;
-                       unsigned char b = lut[i * 8 + i / 4].blue >> 8;
-
-                       odev->funcs->cmap_write(odev, i, r, g, b);
-               }
-               /* Green has one more bit, so add padding with 0 for red and blue. */
-               for (i = OFDRM_GAMMA_LUT_SIZE / 8; i < OFDRM_GAMMA_LUT_SIZE / 4; i++) {
-                       unsigned char r = 0;
-                       unsigned char g = lut[i * 4 + i / 16].green >> 8;
-                       unsigned char b = 0;
-
-                       odev->funcs->cmap_write(odev, i, r, g, b);
-               }
+               drm_crtc_load_gamma_565_from_888(crtc, lut, ofdrm_set_gamma_lut);
                break;
        case DRM_FORMAT_XRGB8888:
        case DRM_FORMAT_BGRX8888:
-               for (i = 0; i < OFDRM_GAMMA_LUT_SIZE; i++) {
-                       unsigned char r = lut[i].red >> 8;
-                       unsigned char g = lut[i].green >> 8;
-                       unsigned char b = lut[i].blue >> 8;
-
-                       odev->funcs->cmap_write(odev, i, r, g, b);
-               }
+               drm_crtc_load_gamma_888(crtc, lut, ofdrm_set_gamma_lut);
                break;
        default:
                drm_warn_once(dev, "Unsupported format %p4cc for gamma correction\n",
@@ -753,9 +733,9 @@ static void ofdrm_crtc_helper_atomic_flush(struct drm_crtc *crtc, struct drm_ato
                const struct drm_format_info *format = sysfb_crtc_state->format;
 
                if (crtc_state->gamma_lut)
-                       ofdrm_device_set_gamma(odev, format, crtc_state->gamma_lut->data);
+                       ofdrm_device_load_gamma(odev, format, crtc_state->gamma_lut->data);
                else
-                       ofdrm_device_set_gamma_linear(odev, format);
+                       ofdrm_device_fill_gamma(odev, format);
        }
 }