On Monday 17 of June 2013 16:06:25 Linus Walleij wrote:
On Sun, Jun 16, 2013 at 10:54 PM, Tomasz Figa tomasz.figa@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.
You're welcome. Thanks for your review.
Best regards, Tomasz