Re: [PATCH v2 0/5] add virt-dma support for imx-sdma

[Sascha Hauer]

On Fri, Jun 08, 2018 at 09:44:45PM +0800, Robin Gong wrote:
> The legacy sdma driver has below limitations or drawbacks:
>   1. Hardcode the max BDs number as "PAGE_SIZE / sizeof(*)", and alloc
>      one page size for one channel regardless of only few BDs needed
>      most time. But in few cases, the max PAGE_SIZE maybe not enough.
>   2. One SDMA channel can't stop immediatley once channel disabled which
>      means SDMA interrupt may come in after this channel terminated.There
>      are some patches for this corner case such as commit "2746e2c389f9",
>      but not cover non-cyclic.
> 
> The common virt-dma overcomes the above limitations. It can alloc bd
> dynamically and free bd once this tx transfer done. No memory wasted or
> maximum limititation here, only depends on how many memory can be requested
> from kernel. For No.2, such issue can be workaround by checking if there
> is available descript("sdmac->desc") now once the unwanted interrupt
> coming. At last the common virt-dma is easier for sdma driver maintain.
> 
> Change from v1:
>   1. split v1 patch into 5 patches.
>   2. remove some unnecessary condition check.
>   3. remove unneccessary 'pending' list.
> 
> Robin Gong (5):
>   dmaengine: imx-sdma: add virt-dma support
>   Revert "dmaengine: imx-sdma: fix pagefault when channel is disabled
>     during interrupt"
>   dmaengine: imx-sdma: remove usless lock
>   dmaengine: imx-sdma: remove the maximum limation for bd numbers
>   dmaengine: imx-sdma: add sdma_transfer_init to decrease code overlap
> 
>  drivers/dma/Kconfig    |   1 +
>  drivers/dma/imx-sdma.c | 392 ++++++++++++++++++++++++++++---------------------
>  2 files changed, 227 insertions(+), 166 deletions(-)

Please put the attached patch in front of your series. It makes the
virt-dma support patch smaller and thus easier to review.

Sascha

--------------------------------8<----------------------------------