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

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Date:   Mon, 11 Jun 2018 12:09:22 +0000
From:   Robin Gong <yibin.gong@....com>
To:     Lucas Stach <l.stach@...gutronix.de>
CC:     "vkoul@...nel.org" <vkoul@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        dl-linux-imx <linux-imx@....com>
Subject: Re: [PATCH v3 0/6] add virt-dma support for imx-sdma


Hi Lucas,
    Thank for your report, I tested it only on SPI, will update to you after try on uart tomorrow.

> 在 2018年6月11日，下午7:01，Lucas Stach <l.stach@...gutronix.de> 写道：
> 
> 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(-)
>>