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

From: Sascha Hauer
Date: Fri Jun 08 2018 - 04:43:24 EST

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.