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Commit c76abab5 authored by Ayan Kumar Halder's avatar Ayan Kumar Halder
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drm: Use horizontal and vertical chroma subsampling factor while calculating... 


drm: Use horizontal and vertical chroma subsampling factor while calculating offsets in the physical address of framebuffer

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: default avatarAyan Kumar halder <ayan.halder@arm.com>
Reviewed-by: default avatarLiviu Dudau <liviu.dudau@arm.com>
Link: https://patchwork.kernel.org/patch/10569263/
parent 065e8c8f

drivers/gpu/drm/drm_fb_cma_helper.c

+9 −2
Original line number Diff line number Diff line
@@ -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;

}