linux-kernel - Re: [PATCH v2] mmc: dw_mmc: Add external dma interface support

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Date:	Mon, 3 Aug 2015 21:23:15 +0800
From:	Shawn Lin <shawn.lin@...k-chips.com>
To:	Heiko Stübner <heiko@...ech.de>,
	linux-rockchip@...ts.infradead.org
Cc:	shawn.lin@...k-chips.com, Ulf Hansson <ulf.hansson@...aro.org>,
	Jaehoon Chung <jh80.chung@...sung.com>,
	Seungwon Jeon <tgih.jun@...sung.com>,
	addy ke <addy.ke@...k-chips.com>,
	Weijun Yang <Weijun.Yang@....com>,
	Kevin Hao <haokexin@...il.com>,
	Scott Branden <sbranden@...adcom.com>,
	Andrew Bresticker <abrestic@...omium.org>,
	Vincent Yang <vincent.yang.fujitsu@...il.com>,
	Stephen Boyd <sboyd@...eaurora.org>, dianders@...omium.org,
	linux-kernel@...r.kernel.org,
	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>,
	Alim Akhtar <alim.akhtar@...sung.com>,
	linux-mmc@...r.kernel.org, Jean Delvare <jdelvare@...e.de>
Subject: Re: [PATCH v2] mmc: dw_mmc: Add external dma interface support

On 2015/8/3 19:17, Heiko Stübner wrote:
> Hi Shawn,
>
> Am Montag, 3. August 2015, 11:27:19 schrieb Shawn Lin:
>> DesignWare MMC Controller can support two types of DMA
>> mode: external dma and internal dma. We get a RK312x platform
>> integrated dw_mmc and ARM pl330 dma controller. This patch add
>> edmac ops to suuport these platforms. I've tested it on RK312x
>> platform with edmac mode and RK3288 platform with idmac mode.
>>
>> Patch is based on next of git://git.linaro.org/people/ulf.hansson/mmc
>>
>> Signed-off-by: Shawn Lin <shawn.lin@...k-chips.com>
>>
>> ---
>>
>> Changes in v2:
>> - Fix typo of dev_info msg
>> - remove unused dmach from declaration of dw_mci_dma_slave
>>
>>   drivers/mmc/host/Kconfig        |  24 +++++-
>>   drivers/mmc/host/dw_mmc-pltfm.c |   4 +
>>   drivers/mmc/host/dw_mmc.c       | 169
>> ++++++++++++++++++++++++++++++++++++++-- include/linux/mmc/dw_mmc.h      |
>> 18 ++++-
>>   4 files changed, 205 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/mmc/host/Kconfig b/drivers/mmc/host/Kconfig
>> index 6a0f9c7..2a66b08 100644
>> --- a/drivers/mmc/host/Kconfig
>> +++ b/drivers/mmc/host/Kconfig
>> @@ -607,16 +607,36 @@ config MMC_DW
>>   	help
>>   	  This selects support for the Synopsys DesignWare Mobile Storage IP
>>   	  block, this provides host support for SD and MMC interfaces, in both
>> -	  PIO and external DMA modes.
>> +	  PIO, internal DMA mode and external DMA modes.
>> +
>> +choice
>> +	prompt "DesignWare MMC transfer mode"
>> +	depends on MMC_DW
>> +
>> +config MMC_DW_PIO
>> +	bool "Use PIO transfers only"
>> +	help
>> +	  Use PIO to transfer data between memory and the hardware.
>> +	  PIO is slower than DMA as it requires CPU instructions to
>> +	  move the data. This has been the traditional default for
>> +	  the DW MCI driver.
>>
>>   config MMC_DW_IDMAC
>>   	bool "Internal DMAC interface"
>> -	depends on MMC_DW
>>   	help
>>   	  This selects support for the internal DMAC block within the Synopsys
>>   	  Designware Mobile Storage IP block. This disables the external DMA
>>   	  interface.
>>
>> +config MMC_DW_EDMAC
>> +	bool "External DMAC interface"
>> +	help
>> +	  This selects support for the external DMAC block outside the Synopsys
>> +	  Designware Mobile Storage IP block. This disables the internal DMA
>> +	  interface.
>> +
>> +endchoice
>> +
> more a drive-by comment:
>
> This should definitly not be a "choice". We're in multiplatform times, where
> you can have support for a multitude of socs using dw_mmc in one kernel. And
> one might want to use pio, one might want to use the internal dma while
> another one might want to use the external dma.
>
> So which dma to use should definitly be decided at runtime and not at compile-
> time.

Thanks for comment, Heiko.
Definitly it should be decided at runtime. So more DT-bindings' patches 
should be
ACKed as well if we want to remove all the compile-time transfer mode.

Hi, Jaehoon Chung
Any suggestion?

>
> Heiko
>
>
>
>


-- 
Shawn Lin


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