Re: [Linux-kernel] [RFC PATCH 5/7] mmc: sh_mobile_sdhi: Add UHS-I mode support

Ulf Hansson
2015-05-05T08:47:10Z

On 5 May 2015 at 10:35, Ben Dooks <ben.dooks-4yDnlxn2s6sWdaTGBSpHTA@public.gmane.org> wrote:
> On 05/05/15 10:56, Ulf Hansson wrote:
>> On 30 April 2015 at 14:32, Ben Hutchings <ben.hutchings-4yDnlxn2s6sWdaTGBSpHTA@public.gmane.org> wrote:
>>> Implement voltage switch, supporting modes up to SDR-50.
>>>
>>> Based on work by Shinobu Uehara, Rob Taylor, William Towle and Ian Molton.
>>>
>>> This uses two voltage regulators, one external and one on the pfc.
>>
>> Why two? If there is a parent child relation ship, that should be
>> handled through the regulator tree, right!? Please elaborate.
>
> The card main power is separate from the IO line voltages.
>
> To get to the high-speed, card power is left at 3.3V and the IO
> voltage is changed to 1.8V.
>
> In the systems we have the power gate is separate from the controls
> for the IO but not integrated into the MMC controller itself.

Okay, that's what I was expecting and hoping for :-)

Then you need to rework $subject patch according to below.

1) Use mmc_regulator_get_supply() to fetch both the I/O voltage
regulator (vqmmc) and the main power regulator (vmmc).Your "vqmmc_ref"
regulator should thus be renamed to "vmmc".
2) The vmmc regulator should not be handled from the
->start_signal_voltage_switch() callback, since it's only vqmmc
voltage levels that should be changed from there.
3) The voltage levels changes for vmmc shall be handled via the
->set_ios() callback.

I suggest you go and have a look in drivers/mmc/host/mmci.c, that
should provide you with a good inspiration.

Kind regards
Uffe
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