linux-kernel - Re: Are media drivers abusing of GFP_DMA? - was: Re: [LSF/MM TOPIC NOTES] x86 ZONE

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Message-ID: <20180507121916.4eb7f5b2@vento.lan>
Date:   Mon, 7 May 2018 12:19:16 -0300
From:   Mauro Carvalho Chehab <mchehab+samsung@...nel.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Fabien Dessenne <fabien.dessenne@...com>,
        Jean-Christophe Trotin <jean-christophe.trotin@...com>,
        Yasunari Takiguchi <Yasunari.Takiguchi@...y.com>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        "Luis R. Rodriguez" <mcgrof@...nel.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org
Subject: Re: Are media drivers abusing of GFP_DMA? - was: Re: [LSF/MM TOPIC
 NOTES] x86 ZONE_DMA love

Em Mon, 07 May 2018 16:26:08 +0300
Laurent Pinchart <laurent.pinchart@...asonboard.com> escreveu:

> Hi Mauro,
> 
> On Saturday, 5 May 2018 19:08:15 EEST Mauro Carvalho Chehab wrote:
> > There was a recent discussion about the use/abuse of GFP_DMA flag when
> > allocating memories at LSF/MM 2018 (see Luis notes enclosed).
> > 
> > The idea seems to be to remove it, using CMA instead. Before doing that,
> > better to check if what we have on media is are valid use cases for it, or
> > if it is there just due to some misunderstanding (or because it was
> > copied from some other code).
> > 
> > Hans de Goede sent us today a patch stopping abuse at gspca, and I'm
> > also posting today two other patches meant to stop abuse of it on USB
> > drivers. Still, there are 4 platform drivers using it:
> > 
> > 	$ git grep -l -E "GFP_DMA\\b" drivers/media/
> > 	drivers/media/platform/omap3isp/ispstat.c
> > 	drivers/media/platform/sti/bdisp/bdisp-hw.c
> > 	drivers/media/platform/sti/hva/hva-mem.c
> > 	drivers/media/spi/cxd2880-spi.c
> > 
> > Could you please check if GFP_DMA is really needed there, or if it is
> > just because of some cut-and-paste from some other place?  
> 
> I started looking at that for the omap3isp driver but Sakari beat me at 
> submitting a patch. GFP_DMA isn't needed for omap3isp.
> 
Thank you both for looking into it.

Regards,
Mauro



Thanks,
Mauro