linux-kernel - Re: [PATCH] drm: Use horizontal and vertical chroma subsampling factor while calculating offsets in the physical address of framebuffer

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Message-ID: <20180820123859.GA2054@arm.com>
Date:   Mon, 20 Aug 2018 13:38:59 +0100
From:   Ayan Halder <ayan.halder@....com>
To:     Liviu Dudau <liviu.dudau@....com>
Cc:     airlied@...ux.ie, linux-kernel@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, seanpaul@...omium.org, nd@....com
Subject: Re: [PATCH] drm: Use horizontal and vertical chroma subsampling
 factor while calculating offsets in the physical address of framebuffer

On Mon, Aug 20, 2018 at 12:03:19PM +0100, Liviu Dudau wrote:
> On Fri, Aug 17, 2018 at 06:33:04PM +0100, Ayan Kumar Halder wrote:
> > 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 the
> 
> drop the extraneous "the" at the end of the line.
> 
> > while calculating the byte position coresponding to the x and y co-ordinates, one needs to be
> 
> and drop the extraneous "be" at the end of this line.
> 
> > divide it with the sampling factor.
> > 
> > Signed-off-by: Ayan Kumar halder <ayan.halder@....com>
> 
> Otherwise, it looks good to me!
> 
> Reviewed-by: Liviu Dudau <liviu.dudau@....com>
>
Thanks Liviu. I will update the commit message and push this in
drm-misc-next.

> Best regards,
> Liviu
> 
> > ---
> >  drivers/gpu/drm/drm_fb_cma_helper.c | 11 +++++++++--
> >  1 file changed, 9 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/drm_fb_cma_helper.c b/drivers/gpu/drm/drm_fb_cma_helper.c
> > index b127061..47e0e2f 100644
> > --- 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;
> >  }
> > -- 
> > 2.7.4
> > 
> 
> -- 
> ====================
> | I would like to |
> | fix the world,  |
> | but they're not |
> | giving me the   |
>  \ source code!  /
>   ---------------
>     ??\_(???)_/??
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