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: <20180820132407.GY907@e110455-lin.cambridge.arm.com>
Date:   Mon, 20 Aug 2018 14:24:07 +0100
From:   Liviu Dudau <liviu.dudau@....com>
To:     Ayan Halder <ayan.halder@....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 01:38:59PM +0100, Ayan Halder wrote:
> 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.

Worth waiting for another review before pushing.

Best regards,
Liviu

> 
> > 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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