drm/fb: avoid setting 0 depth.

airlied · airlied · commit b6a36e5ddf84 · 2019-03-25T09:25:20.000+10:00
If the downscaling fails and we end up with a best_depth of 0, then ignore it. This actually works around a cascade of failure, but it the simplest fix for now. The scaling patch broke the udl driver, as the udl driver doesn't expose planes at all, so gets the two default 32-bit formats, but the udl driver then ask for 16bpp fbdev, and the scaling code falls over. This fixes the udl driver since the scaled depth support was added. Fixes: f4bd542 ("drm/fb-helper: Scale back depth to supported maximum") Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Reviewed-by: Linus Walleij <linus.walleij@linaro.org> Signed-off-by: Dave Airlie <airlied@redhat.com> Link: https://patchwork.freedesktop.org/patch/msgid/20190315014621.21816-2-airlied@gmail.com
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
@@ -1963,7 +1963,7 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper,
 				best_depth = fmt->depth;
 		}
 	}
-	if (sizes.surface_depth != best_depth) {
+	if (sizes.surface_depth != best_depth && best_depth) {
 		DRM_INFO("requested bpp %d, scaled depth down to %d",
 			 sizes.surface_bpp, best_depth);
 		sizes.surface_depth = best_depth;

Original file line number	Diff line number	Diff line change
`@@ -1963,7 +1963,7 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper,`
`1963`	`1963`	`best_depth = fmt->depth;`
`1964`	`1964`	`}`
`1965`	`1965`	`}`
`1966`		`- if (sizes.surface_depth != best_depth) {`
	`1966`	`+ if (sizes.surface_depth != best_depth && best_depth) {`
`1967`	`1967`	`DRM_INFO("requested bpp %d, scaled depth down to %d",`
`1968`	`1968`	`sizes.surface_bpp, best_depth);`
`1969`	`1969`	`sizes.surface_depth = best_depth;`