drm/mgag200: Fix LUT programming for 16bpp

Since there are only 32 (64) distinct color values for each color
in 16bpp Matrox hardware expects those in a 'dense' manner, ie in
the first 32 (64) entries of the respective color.

Signed-off-by: Egbert Eich <eich@suse.de>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/drivers/gpu/drm/mgag200/mgag200_mode.c b/drivers/gpu/drm/mgag200/mgag200_mode.c
index c8983f92bc67..503a414cbdad 100644
--- a/drivers/gpu/drm/mgag200/mgag200_mode.c
+++ b/drivers/gpu/drm/mgag200/mgag200_mode.c
@@ -29,6 +29,7 @@ static void mga_crtc_load_lut(struct drm_crtc *crtc)
         struct mga_crtc *mga_crtc = to_mga_crtc(crtc);
         struct drm_device *dev = crtc->dev;
         struct mga_device *mdev = dev->dev_private;
+        struct drm_framebuffer *fb = crtc->fb;
         int i;
 
         if (!crtc->enabled)
@@ -36,6 +37,28 @@ static void mga_crtc_load_lut(struct drm_crtc *crtc)
 
         WREG8(DAC_INDEX + MGA1064_INDEX, 0);
 
+        if (fb && fb->bits_per_pixel == 16) {
+                int inc = (fb->depth == 15) ? 8 : 4;
+                u8 r, b;
+                for (i = 0; i < MGAG200_LUT_SIZE; i += inc) {
+                        if (fb->depth == 16) {
+                                if (i > (MGAG200_LUT_SIZE >> 1)) {
+                                        r = b = 0;
+                                } else {
+                                        r = mga_crtc->lut_r[i << 1];
+                                        b = mga_crtc->lut_b[i << 1];
+                                }
+                        } else {
+                                r = mga_crtc->lut_r[i];
+                                b = mga_crtc->lut_b[i];
+                        }
+                        /* VGA registers */
+                        WREG8(DAC_INDEX + MGA1064_COL_PAL, r);
+                        WREG8(DAC_INDEX + MGA1064_COL_PAL, mga_crtc->lut_g[i]);
+                        WREG8(DAC_INDEX + MGA1064_COL_PAL, b);
+                }
+                return;
+        }
         for (i = 0; i < MGAG200_LUT_SIZE; i++) {
                 /* VGA registers */
                 WREG8(DAC_INDEX + MGA1064_COL_PAL, mga_crtc->lut_r[i]);