drm: Use horizontal and vertical chroma subsampling factor while calculating offsets...

For multi-planar formats, while calculating offsets in planes with index greater than 0
(ie second plane, third plane, etc), one needs to divide (src_x * cpp) with horizontal
chroma subsampling factor and (src_y * pitch) with vertical chroma subsampling factor.

The reason being that the planes contain subsampled (ie reduced) data (by a factor of 2) and thus
while calculating the byte position coresponding to the x and y co-ordinates, one needs to
divide it with the sampling factor.

Signed-off-by: Ayan Kumar halder <ayan.halder@arm.com>
Reviewed-by: Liviu Dudau <liviu.dudau@arm.com>
Link: https://patchwork.kernel.org/patch/10569263/

diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c b/drivers/gpu/drm/drm_fb_cma_helper.c
index b127061..47e0e2f 100644 (file)
--- a/drivers/gpu/drm/drm_fb_cma_helper.c
+++ b/drivers/gpu/drm/drm_fb_cma_helper.c
@@ -86,14 +86,21 @@ dma_addr_t drm_fb_cma_get_gem_addr(struct drm_framebuffer *fb,
 {
        struct drm_gem_cma_object *obj;
        dma_addr_t paddr;
+       u8 h_div = 1, v_div = 1;
 
        obj = drm_fb_cma_get_gem_obj(fb, plane);
        if (!obj)
                return 0;
 
        paddr = obj->paddr + fb->offsets[plane];
-       paddr += fb->format->cpp[plane] * (state->src_x >> 16);
-       paddr += fb->pitches[plane] * (state->src_y >> 16);
+
+       if (plane > 0) {
+               h_div = fb->format->hsub;
+               v_div = fb->format->vsub;
+       }
+
+       paddr += (fb->format->cpp[plane] * (state->src_x >> 16)) / h_div;
+       paddr += (fb->pitches[plane] * (state->src_y >> 16)) / v_div;
 
        return paddr;
 }