drm/nouveau/kms/nv50-: Fix disabling dithering

While we expose the ability to turn off hardware dithering for nouveau,
we actually make the mistake of turning it on anyway, due to
dithering_depth containing a non-zero value if our dithering depth isn't
also set to 6 bpc.

So, fix it by never enabling dithering when it's disabled.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Ben Skeggs <bskeggs@redhat.com>
Acked-by: Dave Airlie <airlied@gmail.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200627194657.156514-6-lyude@redhat.com

diff --git a/drivers/gpu/drm/nouveau/dispnv50/head.c b/drivers/gpu/drm/nouveau/dispnv50/head.c
index 8f64556..ed68195 100644 (file)
--- a/drivers/gpu/drm/nouveau/dispnv50/head.c
+++ b/drivers/gpu/drm/nouveau/dispnv50/head.c
@@ -84,18 +84,20 @@ nv50_head_atomic_check_dither(struct nv50_head_atom *armh,
 {
        u32 mode = 0x00;
 
-       if (asyc->dither.mode == DITHERING_MODE_AUTO) {
-               if (asyh->base.depth > asyh->or.bpc * 3)
-                       mode = DITHERING_MODE_DYNAMIC2X2;
-       } else {
-               mode = asyc->dither.mode;
-       }
+       if (asyc->dither.mode) {
+               if (asyc->dither.mode == DITHERING_MODE_AUTO) {
+                       if (asyh->base.depth > asyh->or.bpc * 3)
+                               mode = DITHERING_MODE_DYNAMIC2X2;
+               } else {
+                       mode = asyc->dither.mode;
+               }
 
-       if (asyc->dither.depth == DITHERING_DEPTH_AUTO) {
-               if (asyh->or.bpc >= 8)
-                       mode |= DITHERING_DEPTH_8BPC;
-       } else {
-               mode |= asyc->dither.depth;
+               if (asyc->dither.depth == DITHERING_DEPTH_AUTO) {
+                       if (asyh->or.bpc >= 8)
+                               mode |= DITHERING_DEPTH_8BPC;
+               } else {
+                       mode |= asyc->dither.depth;
+               }
        }
 
        asyh->dither.enable = mode;