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

Jaehoon Chung
2014-08-27T03:48:17Z

Hi, Doug,

On 08/26/2014 12:25 AM, Doug Anderson wrote:
> 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 think you're mis-understanding for it.
Right, It's described at exynos5420, but it's not connected.
Exynos4 series are also described, but we used the broken card detection scheme and power used one of "always-on" powers.
Because Card-detection rail need to enable as "always-on".

We don't need to consider this. I checked the circuit, this patch didn't need.

exynos5 also used the gpio-pin for card-detection. And we can use the slot-gpio API.

Best Regards,
Jaehoon Chung

>
> 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.
>