Re: [PATCH V2 3/3] mmc: dw_mmc: Dont cut off vqmmc and vmmc

Doug Anderson
2014-08-25T15:25:02Z

Jaehoon,

On Mon, Aug 25, 2014 at 1:50 AM, Jaehoon Chung <jh80.chung@samsung.com> wrote:
> On 08/25/2014 05:13 PM, Ulf Hansson wrote:
>> On 22 August 2014 20:27, Sonny Rao <sonnyrao@chromium.org> wrote:
>>> On Fri, Aug 22, 2014 at 8:31 AM, Ulf Hansson <ulf.hansson@linaro.org> wrote:
>>>> On 22 August 2014 15:47, Yuvaraj Kumar C D <yuvaraj.cd@gmail.com> wrote:
>>>>> Exynos 5250 and 5420 based boards uses built-in CD# line for card
>>>>> detection.But unfortunately CD# line is on the same voltage rails
>>>>> as of I/O voltage rails. When we cut off vqmmc,the consequent card
>>>>> detection will break in these boards.
>
> I didn't know that use CD# line for card detect.
> And if CD# voltage rails and I/O voltage rail are same voltage, it doesn't make sense.
> Which card is used with same voltages? (eMMC? SD? SDIO?)
>
> Well, I have checked Exynos5250 and 5420, but it looks like not same rails.

I'm not sure I totally understood what you said. In my manual I have
a table titled "Table 2-1 Exynos 5420 Pin List". Look in this table
for XMMC2CDN and XMMC2DATA_0. Look to the right of the table and
you'll see the power domain. For both it shows VDDQ_MMC2. If that
doesn't mean that the two are in the same voltage domain then I don't
know what does. Can you point to any examples where they have
different voltage domains?

I agree that what exynos does is not sensible, but that's what it is.

>>>> I am not sure I follow here.
>>>>
>>>> Is the card detect mechanism handled internally by the dw_mmc controller?
>>>
>>> Yes
>
> What card detect mechanism?

The dw_mmc controller has a way to read the card detect, right?
That's internal to the controller. The alternative would be to use a
generic GPIO for card detect.