Re: [PATCH] drm/omap: fix tiled buffer stride calculations

From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
To: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: Jyri Sarha <jsarha@ti.com>, dri-devel@lists.freedesktop.org
Subject: Re: [PATCH] drm/omap: fix tiled buffer stride calculations
Date: Thu, 18 May 2017 15:32:45 +0300	[thread overview]
Message-ID: <5891985.kG72mX4jGs@avalon> (raw)
In-Reply-To: <a534d2b3-72d8-a7a2-dc57-a956cd94d275@ti.com>

Hi Tomi,

On Thursday 18 May 2017 14:34:09 Tomi Valkeinen wrote:
> On 18/05/17 14:25, Laurent Pinchart wrote:
> > On Thursday 18 May 2017 14:14:35 Tomi Valkeinen wrote:
> >> On 18/05/17 13:59, Laurent Pinchart wrote:
> >>> On Thursday 18 May 2017 13:28:26 Tomi Valkeinen wrote:
> >>>> omap_gem uses page alignment for buffer stride. The related
> >>>> calculations
> >>>> are a bit off, though, as byte stride of 4096 gets aligned to 8192,
> >>>> instead of 4096. This patch fixes those calculations.
> >>>> 
> >>>> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
> >>>> ---
> >>>> 
> >>>>  drivers/gpu/drm/omapdrm/omap_gem.c | 4 ++--
> >>>>  1 file changed, 2 insertions(+), 2 deletions(-)
> >>>> 
> >>>> diff --git a/drivers/gpu/drm/omapdrm/omap_gem.c
> >>>> b/drivers/gpu/drm/omapdrm/omap_gem.c index 13abf221d153..4c41000ff4c4
> >>>> 100644
> >>>> --- a/drivers/gpu/drm/omapdrm/omap_gem.c
> >>>> +++ b/drivers/gpu/drm/omapdrm/omap_gem.c
> >>>> @@ -182,7 +182,7 @@ static void evict_entry(struct drm_gem_object *obj,
> >>>>  	size_t size = PAGE_SIZE * n;
> >>>>  	loff_t off = mmap_offset(obj) +
> >>>>  			(entry->obj_pgoff << PAGE_SHIFT);
> >>>> -	const int m = 1 + ((omap_obj->width << fmt) / PAGE_SIZE);
> >>>> +	const int m = 1 + (((omap_obj->width - 1) << fmt) /
> >>>> PAGE_SIZE);
> >>> 
> >>> How about
> >>> 
> >>> 	int m = round_up(omap_obj->width << fmt, PAGE_SIZE);
> >>> 
> >>> instead of open-coding it ? I find that a bit easier to understand.
> >> 
> >> That should be:
> >> 
> >> round_up(omap_obj->width << fmt, PAGE_SIZE) / PAGE_SIZE;
> > 
> > Sorry, I meant DIV_ROUND_UP, not round_up.
> 
> Ah, of course. Not my day... =)
> 
> From: Tomi Valkeinen <tomi.valkeinen@ti.com>
> Date: Thu, 18 May 2017 11:51:51 +0300
> Subject: [PATCH] drm/omap: fix tiled buffer stride calculations
> 
> omap_gem uses page alignment for buffer stride. The related calculations
> are a bit off, though, as byte stride of 4096 gets aligned to 8192,
> instead of 4096.
> 
> This patch changes the code to use DIV_ROUND_UP(), which fixes those
> calculations and makes them more readable.
> 
> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@ti.com>

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> diff --git a/drivers/gpu/drm/omapdrm/omap_gem.c
> b/drivers/gpu/drm/omapdrm/omap_gem.c index 13abf221d153..5c5c86ddd6f4
> 100644
> --- a/drivers/gpu/drm/omapdrm/omap_gem.c
> +++ b/drivers/gpu/drm/omapdrm/omap_gem.c
> @@ -182,7 +182,7 @@ static void evict_entry(struct drm_gem_object *obj,
>  	size_t size = PAGE_SIZE * n;
>  	loff_t off = mmap_offset(obj) +
>  			(entry->obj_pgoff << PAGE_SHIFT);
> -	const int m = 1 + ((omap_obj->width << fmt) / PAGE_SIZE);
> +	const int m = DIV_ROUND_UP(omap_obj->width << fmt, PAGE_SIZE);
> 
>  	if (m > 1) {
>  		int i;
> @@ -424,7 +424,7 @@ static int fault_2d(struct drm_gem_object *obj,
>  	 * into account in some of the math, so figure out virtual stride
>  	 * in pages
>  	 */
> -	const int m = 1 + ((omap_obj->width << fmt) / PAGE_SIZE);
> +	const int m = DIV_ROUND_UP(omap_obj->width << fmt, PAGE_SIZE);
> 
>  	/* We don't use vmf->pgoff since that has the fake offset: */
>  	pgoff = (vmf->address - vma->vm_start) >> PAGE_SHIFT;

-- 
Regards,

Laurent Pinchart

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