linux-kernel - Re: OMAPFB: CMA allocation failures

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Date:	Wed, 30 Oct 2013 14:19:32 +0200
From:	Tomi Valkeinen <tomi.valkeinen@...com>
To:	Ивайло Димитров 
	<freemangordon@....bg>
CC:	Minchan Kim <minchan@...nel.org>, <pavel@....cz>, <sre@...ian.org>,
	<pali.rohar@...il.com>, <pc+n900@...f.org>,
	<linux-kernel@...r.kernel.org>, <linux-mm@...ck.org>
Subject: Re: OMAPFB: CMA allocation failures

On 2013-10-29 14:47, Ивайло Димитров wrote:

> However, back to omapfb - my understanding is that the way it uses CMA (in its current form) is
> prone to allocation failures way beyond acceptable. 
> 
> Tomi, what do you think about adding module parameters to allow pre-allocating framebuffer memory
> from CMA during boot? Or re-implement VRAM allocator to use CMA? As a good side-effect 
> OMAPFB_GET_VRAM_INFO will no longer return fake values.

I really dislike the idea of adding the omap vram allocator back. Then
again, if the CMA doesn't work, something has to be done.

Pre-allocating is possible, but that won't work if there's any need to
re-allocating the framebuffers. Except if the omapfb would retain and
manage the pre-allocated buffers, but that would just be more or less
the old vram allocator again.

So, as I see it, the best option would be to have the standard dma_alloc
functions get the memory for omapfb from a private pool, which is not
used for anything else.

I wonder if that's possible already? It sounds quite trivial to me.

 Tomi

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