[alsa-devel] [RFC PATCH 00/11] ARM: s3c64xx: Let amba-pl08x driver handle DMA

Linus Walleij linus.walleij at linaro.org
Mon Jun 17 16:06:25 CEST 2013

On Sun, Jun 16, 2013 at 10:54 PM, Tomasz Figa <tomasz.figa at gmail.com> wrote:

> One of the biggest roadblocks on the way of S3C64xx to DeviceTree support
> is its DMA driver, which is completely platform-specific and provides
> private API (s3c-dma), not even saying that its design is completely
> against multiplatform-awareness.
> The DMA controller present on this SoC series is a custom variant
> of ARM PrimeCell PL080 modified by Samsung to add some extra features.
> It is mostly compatible with original PL080, except:
>  - CH_CONTROL2 register is added between CH_CONTROL and CH_CONFIG,
>  - offset of CH_CONFIG register is different,
>  - transfer size field is moved from CH_CONTROL to CH_CONTROL2,
>  - transfer size field is extended to 24 bits, allowing much bigger
>      single transfer,
>  - LLI consists of one more word, to account for CH_CONTROL2 register.
> Since all the rest is fully compatible with standard PL080 there is no
> point in having separate driver just for this single variant, so I decided
> to look into adding support for it to the amba-pl08x driver.
> There was already some attempt to achieve this before, but this was before
> Russel's big rework of the driver to use virtual channels, making the old
> patches being not much of use.
> This RFC series is a proof of concept that I managed to make during last
> days of hacking. Except one patch adding clkdev lookup to clock driver
> (which is being replaced with a CCF-compliant driver ATM), this is enough
> to get memcpy and slave transfers to work on S3C64xx.
> I have tested this on Mini6410 and SMDK6410 boards using dmatest for
> memcpy and Samsung I2S with madplay/aplay for slave transfers.
> Unfortunately I do not have access to other platforms with PL08x so
> I could not test for any regressions introduced on them.
> Credits for two patches go to Alban Bedel, who made a series fixing this
> driver to make it usable with audio drivers. I rebased his patches on top
> of mine and corrected coding style a bit.
> OK, that's all. Any comments are welcome. Feel free to start throwing eggs
> and tomatoes if you find this awful, but I won't be upset if I get some
> Tested-by or Acked-by as well. ;)

I've waited for a long time for this to happen, thank you very much for
doing this.

Linus Walleij

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