Re: [PATCH] Revert "mmc: dw_mmc: Add check for IDMAC configuration"

Chris Ball
2012-09-19T06:03:06Z

Hi,

On Mon, Sep 17 2012, Will Newton wrote:
> On Tue, Sep 11, 2012 at 3:23 AM, Seungwon Jeon <tgih.jun@samsung.com> wrote:
>> This reverts commit 94c6cee91(Add check for IDMAC configuration).
>> Synopsys says that only if internal dmac is not present, optional
>> external dma interface is present. When internal dmac is present,
>> '0' value in DMA_INTERFACE of HCON is reasonable. DMA_INTERFACE
>> indicates external dma interface. And idmac initialization is
>> prohibited now. So, let's revert this commit.
>>
>> CC: Girish K S <girish.shivananjappa@linaro.org>
>> Signed-off-by: Seungwon Jeon <tgih.jun@samsung.com>
>> ---
>> drivers/mmc/host/dw_mmc.c | 15 ++-------------
>> 1 files changed, 2 insertions(+), 13 deletions(-)
>
> I think this revert is a good idea. The original patch tries to check
> whether IDMAC is supported and falls back to PIO, but it is not clear
> to me that HCON gives you the appropriate information to do this (at
> least in my version of the manual, I have not tried to clarify this
> with Synopsys). Also falling back to PIO mode seems like it would
> provide pretty awful performance, I would not expect to see instances
> of this block with no DMA support anywhere other than FPGA so
> configuring with IDMAC without it's presence would be a serious
> misconfiguration in any case.
>
> Acked-by: Will Newton <will.newton@imgtec.com>

Thanks, pushed to mmc-next for 3.7.

- Chris.
--
Chris Ball <cjb@laptop.org> <http://printf.net/>
One Laptop Per Child