Re: [PATCH] mmc: sdhci-tegra: Set DMA mask

From	Stephen Warren <swarren@wwwdotorg.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH] mmc: sdhci-tegra: Set DMA mask
Date	2016-02-24 18:10 +0100
Message-ID	<r5L6O-7D3-9@gated-at.bofh.it> (permalink)
References	<r5DLX-2n7-1@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On 02/24/2016 02:11 AM, Alexandre Courbot wrote:
> On T210, the sdhci controller can address more than 32 bits of address
> space. Failing to express this fact results in the use of bounce
> buffers and affects performance.
>
> Signed-off-by: Alexandre Courbot <acourbot@nvidia.com>
> ---
> I am pretty sure this one is wrong in some way, but just to get the ball
> rolling as the use of bounce buffers is currently quite heavy on Jetson TX1.
>
> Thierry, Stephen, could you confirm that I got the DMA masks correctly? I
> am not sure about the actual addressable size on TX1, and also suspect TK1 can
> also address more than 32 bits.

I don't actually know what the HW capabilities are. You had best track 
down one of NVIDIA's HW designers/integrators; hopefully the can provide 
all kinds of gory details.

One thing I will say: in U-Boot, we deliberately clip usable RAM size to 
2GiB so that the PA of all RAM fits into 32 bits, specifically because 
of IO controllers that can only address 32 bits. It is possible this was 
only required on earlier chips and T210 fixed it though; I don't know. 
Equally, I suppose the restriction might only apply to a subset of IO 
controllers (USB would be another one relevant to U-Boot).

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[PATCH] mmc: sdhci-tegra: Set DMA mask Alexandre Courbot <acourbot@nvidia.com> - 2016-02-24 10:20 +0100
  Re: [PATCH] mmc: sdhci-tegra: Set DMA mask Arnd Bergmann <arnd@arndb.de> - 2016-02-24 13:40 +0100
    Re: [PATCH] mmc: sdhci-tegra: Set DMA mask Alexandre Courbot <gnurou@gmail.com> - 2016-02-25 11:00 +0100
      Re: [PATCH] mmc: sdhci-tegra: Set DMA mask Arnd Bergmann <arnd@arndb.de> - 2016-02-25 16:00 +0100
        Re: [PATCH] mmc: sdhci-tegra: Set DMA mask Alexandre Courbot <gnurou@gmail.com> - 2016-02-26 08:30 +0100
          Re: [PATCH] mmc: sdhci-tegra: Set DMA mask Arnd Bergmann <arnd@arndb.de> - 2016-02-26 12:40 +0100
            Re: [PATCH] mmc: sdhci-tegra: Set DMA mask Alexandre Courbot <acourbot@nvidia.com> - 2016-03-01 05:30 +0100
  Re: [PATCH] mmc: sdhci-tegra: Set DMA mask Stephen Warren <swarren@wwwdotorg.org> - 2016-02-24 18:10 +0100

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