From: Russell King - ARM Linux <linux@armlinux.org.uk>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Mikko Perttunen <cyndis@kapsi.fi>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
dri-devel <dri-devel@lists.freedesktop.org>,
Mikko Perttunen <mperttunen@nvidia.com>,
Thierry Reding <thierry.reding@gmail.com>,
linux-tegra@vger.kernel.org,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH] [RFC] gpu: host1x: shut up warning about DMA API misuse
Date: Thu, 20 Apr 2017 10:49:32 +0100 [thread overview]
Message-ID: <20170420094932.GM17774@n2100.armlinux.org.uk> (raw)
In-Reply-To: <CAK8P3a3JJrA_4Zur47ngWmR7VeKBopJLNZCaqOPzzmnFoV3=Ew@mail.gmail.com>
On Thu, Apr 20, 2017 at 10:25:01AM +0200, Arnd Bergmann wrote:
> On Thu, Apr 20, 2017 at 9:02 AM, Mikko Perttunen <cyndis@kapsi.fi> wrote:
> > I think we have a "policy" on Tegra that the DMA API will never allocate
> > using the IOMMU (Thierry can elaborate on this), which is why I wrote the
> > code with that assumption. Essentially, we have made the DMA API into the
> > API that allocates CPU-visible memory.
>
> I don't think this can be a per-platform policy.
>
> > Considering that, I'm wondering if we can just have a temporary local
> > dma_addr_t and then cast that to phys_addr_t, combined with a good comment?
>
> That was my first approach, and it does address the warning, but
> I did not send it because it still felt too wrong.
Sounds to me like the warning is justified - it's saying that there's
something not right here which could be a problem. So I'd say, don't
fix the warning, it's doing its job, highlighting a potential problem
with the code.
(Consider hiding the warning and then running on a platform where the
assumptions are broken.)
--
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
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next prev parent reply other threads:[~2017-04-20 9:49 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-04-19 18:24 [PATCH] [RFC] gpu: host1x: shut up warning about DMA API misuse Arnd Bergmann
2017-04-20 7:02 ` Mikko Perttunen
2017-04-20 8:25 ` Arnd Bergmann
2017-04-20 9:44 ` Mikko Perttunen
2017-04-20 10:02 ` Arnd Bergmann
2017-04-20 10:14 ` Mikko Perttunen
2017-04-20 9:49 ` Russell King - ARM Linux [this message]
2017-04-20 10:05 ` Arnd Bergmann
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