Re: [PATCH 08/19] mmc: sdhi: Enable the driver on all ARM platforms

[Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>]

Hello.

On 29-10-2013 13:52, Laurent Pinchart wrote:

>>> Renesas ARM platforms are transitioning from single-platform to
>>> multi-platform kernels using the new ARCH_SHMOBILE_MULTI. Make the
>>> driver available on all ARM platforms to enable it on both ARCH_SHMOBILE
>>> and ARCH_SHMOBILE_MULTI and increase build testing coverage.

>>> Cc: Chris Ball <cjb@laptop.org>
>>> Cc: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
>>> Cc: Ian Molton <ian@mnementh.co.uk>
>>> Cc: linux-mmc@vger.kernel.org
>>> Signed-off-by: Laurent Pinchart
>>> <laurent.pinchart+renesas@ideasonboard.com>
[...]

>>> diff --git a/drivers/mmc/host/tmio_mmc_dma.c
>>> b/drivers/mmc/host/tmio_mmc_dma.c index 65edb4a..535bc35 100644
>>> --- a/drivers/mmc/host/tmio_mmc_dma.c
>>> +++ b/drivers/mmc/host/tmio_mmc_dma.c
>>> @@ -28,7 +28,7 @@ void tmio_mmc_enable_dma(struct tmio_mmc_host *host,
>>> bool enable)>
>>>   	if (!host->chan_tx || !host->chan_rx)
>>>   	
>>>   		return;
>>>
>>> -#if defined(CONFIG_SUPERH) || defined(CONFIG_ARCH_SHMOBILE)
>>> +#if defined(CONFIG_SUPERH) || defined(CONFIG_ARM)

>> I'm not sure about this one. In principle DMA so far is only used on SDHI
>> with TMIO. But this #if was for a theoretical case, when a TMIO MMC IP
>> inside an MFD is also used with DMA. Bus since I had no indormation about
>> whether the CTL_DMA_ENABLE register was SDHI specific or not, I put it
>> under an #if for the time being. In any case, I don't think making it
>> #ifdef CONFIG_ARM makes much sense. We can either remove the #if
>> completely, or keep it to limit the scope of this write to sh-mobile
>> arches.

> SUPERH || ARCH_SHMOBILE covers all the platforms this driver currently builds
> on. Now that we're adding ARCH_SHMOBILE_MULTI the #if needs to cover that case
> as well. I'm fine with limiting the CTL_DMA_ENABLE write to SUPERH only (which
> would modify the driver's behaviour)

    I'm afraid that would break the driver's ability to work in DMA mode on 
SH-Mobile SoCs.

> or enabling it unconditionally, but I
> don't think adding a defined(CONFIG_ARCH_SHMOBILE_MULTI) to the above #if
> makes sense, unless there's a plan to add support for DMA for non-SH
> (including both SUPERH and ARCH_SHMOBILE) platforms.

    Not only the plan -- I have already posted the patches to do it for 
R8A777x, and Simon has queued them for 3.13.

>>>   	/* Switch DMA mode on or off - SuperH specific? */
>>>   	sd_ctrl_write16(host, CTL_DMA_ENABLE, enable ? 2 : 0);
>>>
>>>   #endif

WBR, Sergei