linux-kernel - Re: [PATCH v2 1/3] mmc: sdhci: add support for using external DMA devices

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Message-ID: <22591bc4-ea34-dcc6-a3d5-8a75e890ff2b@rock-chips.com>
Date:   Fri, 30 Nov 2018 09:15:24 +0800
From:   Shawn Lin <shawn.lin@...k-chips.com>
To:     Chunyan Zhang <zhang.lyra@...il.com>,
        Adrian Hunter <adrian.hunter@...el.com>
Cc:     shawn.lin@...k-chips.com, Chunyan Zhang <zhang.chunyan@...aro.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        linux-mmc@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>, Mark Brown <broonie@...nel.org>,
        kishon@...com, nsekhar@...com
Subject: Re: [PATCH v2 1/3] mmc: sdhci: add support for using external DMA
 devices

On 2018/11/29 17:59, Chunyan Zhang wrote:
> Hi Adrian,
> 
> On Thu, 29 Nov 2018 at 15:36, Adrian Hunter <adrian.hunter@...el.com> wrote:
>>
>> On 29/11/18 8:22 AM, Chunyan Zhang wrote:
>>> On Tue, 20 Nov 2018 at 21:41, Adrian Hunter <adrian.hunter@...el.com> wrote:
>>>>
>>>> On 12/11/18 9:26 AM, Chunyan Zhang wrote:
>>>>> Some standard SD host controllers can support both external dma
>>>>> controllers as well as ADMA/SDMA in which the SD host controller
>>>>> acts as DMA master. TI's omap controller is the case as an example.
>>>>>
>>>>> Currently the generic SDHCI code supports ADMA/SDMA integrated in
>>>>> the host controller but does not have any support for external DMA
>>>>> controllers implemented using dmaengine, meaning that custom code is
>>>>> needed for any systems that use an external DMA controller with SDHCI.
>>>>
>>>> I still think you probably need to reset the DMA if there are transfer
>>>> errors - perhaps you could comment on that.  Also there are some comments below.
>>>
>>> With regard to "transfer error", do you mean if
>>> sdhci_external_dma_setup() failed?
>>
>> No, I mean any error interrupt that can leave the DMA uncompleted.  For
>> SDHCI, resetting the data circuit cleans that up, but presumably something
>> is needed for external DMA?
> 
> Yes, it should need a dmaengine_terminate_all().
> 

No, dmaengine_terminate_all is deprecated for quite a long time.
Please use dmaengine_terminate_{async, sync}() instead.

See Documentation/dmaengine/client.txt


> How about adding that at here (I will wrap it up of course):
> https://elixir.bootlin.com/linux/v4.19.5/source/drivers/mmc/host/sdhci.c#L2553
> 
> Is there somewhere else I'm missing?
> 
> Thanks,
> Chunyan
> 
>