Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1627248

Re: [PATCH] [RFC] gpu: host1x: shut up warning about DMA API misuse

Show all headers | View raw

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
according to speedtest.net.

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH] [RFC] gpu: host1x: shut up warning about DMA API misuse Arnd Bergmann <arnd@arndb.de> - 2017-04-19 20:30 +0200
  Re: [PATCH] [RFC] gpu: host1x: shut up warning about DMA API misuse Mikko Perttunen <cyndis@kapsi.fi> - 2017-04-20 09:10 +0200
    Re: [PATCH] [RFC] gpu: host1x: shut up warning about DMA API misuse Arnd Bergmann <arnd@arndb.de> - 2017-04-20 10:30 +0200
      Re: [PATCH] [RFC] gpu: host1x: shut up warning about DMA API misuse Mikko Perttunen <cyndis@kapsi.fi> - 2017-04-20 11:50 +0200
        Re: [PATCH] [RFC] gpu: host1x: shut up warning about DMA API misuse Arnd Bergmann <arnd@arndb.de> - 2017-04-20 12:10 +0200
          Re: [PATCH] [RFC] gpu: host1x: shut up warning about DMA API misuse Mikko Perttunen <cyndis@kapsi.fi> - 2017-04-20 12:20 +0200
      Re: [PATCH] [RFC] gpu: host1x: shut up warning about DMA API misuse Russell King - ARM Linux <linux@armlinux.org.uk> - 2017-04-20 11:50 +0200
        Re: [PATCH] [RFC] gpu: host1x: shut up warning about DMA API misuse Arnd Bergmann <arnd@arndb.de> - 2017-04-20 12:10 +0200

csiph-web