linux-kernel - Re: [PATCH v3 0/6] add virt-dma support for imx-sdma

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Date:   Mon, 11 Jun 2018 13:01:17 +0200
From:   Lucas Stach <l.stach@...gutronix.de>
To:     Robin Gong <yibin.gong@....com>, vkoul@...nel.org,
        s.hauer@...gutronix.de, dan.j.williams@...el.com
Cc:     dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, linux-imx@....com
Subject: Re: [PATCH v3 0/6] add virt-dma support for imx-sdma

Hi Robin,

this series breaks serial DMA for me. I wasn't able to dig in deeper
yet. Please let me know if you can test/reproduce at your side, if not
I'll try to find some time to collect some more debug info.

Regards,
Lucas

Am Montag, den 11.06.2018, 22:59 +0800 schrieb Robin Gong:
> 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 v2:
>   1. include Sascha's patch to make the main patch easier to review.
>      Thanks Sacha.
>   2. remove useless 'desc'/'chan' in struct sdma_channe.
> 
> Change from v1:
>   1. split v1 patch into 5 patches.
>   2. remove some unnecessary condition check.
>   3. remove unnecessary '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(-)
> 
> -- 
> 2.7.4
> 
> 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
> 
> Sascha Hauer (1):
>   dmaengine: imx-sdma: factor out a struct sdma_desc from struct
>     sdma_channel
> 
>  drivers/dma/Kconfig    |   1 +
>  drivers/dma/imx-sdma.c | 391 ++++++++++++++++++++++++++++---------------------
>  2 files changed, 226 insertions(+), 166 deletions(-)
>