Re: [PATCH V5 1/2] mmc: dw_mmc: exynos: Support eMMC's HS400 mode

[Jaehoon Chung <jh80.chung@samsung.com>]

Dear, Rob.

On 02/25/2015 11:38 PM, Rob Herring wrote:
> On Wed, Jan 28, 2015 at 8:41 PM, Alim Akhtar <alim.akhtar@samsung.com> wrote:
>> From: Seungwon Jeon <tgih.jun@samsung.com>
>>
>> Implements HS400 mode support for exynos host driver.
>> This also include some updates as new mode is added.
>>
>> Signed-off-by: Seungwon Jeon <tgih.jun@samsung.com>
>> Signed-off-by: Alim Akhtar <alim.akhtar@samsung.com>
>> [Alim: addressed review comments]
>> ---
>>  .../devicetree/bindings/mmc/exynos-dw-mshc.txt     |    7 +
>>  drivers/mmc/host/dw_mmc-exynos.c                   |  185 ++++++++++++++++----
>>  drivers/mmc/host/dw_mmc-exynos.h                   |   19 +-
>>  drivers/mmc/host/dw_mmc.c                          |   16 +-
>>  drivers/mmc/host/dw_mmc.h                          |    2 +
>>  5 files changed, 195 insertions(+), 34 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/mmc/exynos-dw-mshc.txt b/Documentation/devicetree/bindings/mmc/exynos-dw-mshc.txt
>> index ee4fc05..aad9844 100644
>> --- a/Documentation/devicetree/bindings/mmc/exynos-dw-mshc.txt
>> +++ b/Documentation/devicetree/bindings/mmc/exynos-dw-mshc.txt
>> @@ -36,6 +36,8 @@ Required Properties:
>>    in transmit mode and CIU clock phase shift value in receive mode for double
>>    data rate mode operation. Refer notes below for the order of the cells and the
>>    valid values.
>> +* samsung,dw-mshc-hs400-timing: Specifies the value of CIU TX and RX clock phase
>> +  shift value for hs400 mode operation.
> 
> What are the units?

Do you means what is "sumsung,dw-mshci-hs400-timing" unit?
It's timing value for eMMC/SD/SDIO clock phase.(It's exynos specific value.)
Using timing value can shift the H/W clock phase.
If invalid timing value is set, eMMC/SD/SDIO can produce the CRC error.

Do you think it can't include into device-tree?
I want to know your thinking. let me know, plz.

Best Regards,
Jaehoon Chung

> 
> Rob
>