Re: [RFC] mmc: core: add the capability for broken voltage

[Adrian Hunter <adrian.hunter@intel.com>]

On 17/01/12 11:05, Kyungmin Park wrote:
> On 1/17/12, Adrian Hunter <adrian.hunter@intel.com> wrote:
>> On 16/01/12 10:49, Jaehoon Chung wrote:
>>> This patch is added the MMC_CAP2_BROKEN_VOLTAGE.
>>>
>>> if the voltage didn't satisfy between min_uV and max_uV,
>>
>> Why is the fixed voltage not in the acceptable range for the card?
>> Doesn't that risk breaking the card?
> Hi Adrian,
> 
> I don't know, they uses the not supported voltage. but it's worked
> properly for long time.

I wonder if there is a generic problem here that this fix hides.
It would be nice to have an explanation.  Do you know:
	- what is the fixed voltage?
	- is it supplying VCC or VCCQ?
	- what is the contents of the OCR register?

> Galaxy S2 also uses the same voltage as ours.
> 
> I also think the modify the regulator framework to support voltage
> change at fixed regulator. but it's not good idea and doesn't match
> the regulator concept. so modify the sdhci codes to support our
> boards.
> 
> Thank you,
> Kyungmin Park
>>
>>> try to change the voltage in core.c.
>>> When change the voltage, maybe use the regulator_set_voltage().
>>>
>>> In regulator_set_voltage(), check the below condition.
>>>
>>> 	/* sanity check */
>>> 	if (!rdev->desc->ops->set_voltage &&
>>> 	    !rdev->desc->ops->set_voltage_sel) {
>>> 		ret = -EINVAL;
>>> 		goto out;
>>> 	}
>>>
>>> If Some-board should use the fixed-regulator, always return -EINVAL.
>>> Then, eMMC didn't initialize always.
>>>
>>> So if use the fixed-regulator or etc, we need to add the
>>> MMC_CAP2_BROKEN_VOLTAGE.
>>>
>>> Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
>>> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
>>> ---
>>>  drivers/mmc/core/core.c  |    4 ++++
>>>  include/linux/mmc/host.h |    1 +
>>>  2 files changed, 5 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
>>> index bec0bf2..6848789 100644
>>> --- a/drivers/mmc/core/core.c
>>> +++ b/drivers/mmc/core/core.c
>>> @@ -1121,6 +1121,10 @@ int mmc_regulator_set_ocr(struct mmc_host *mmc,
>>>  		 * might not allow this operation
>>>  		 */
>>>  		voltage = regulator_get_voltage(supply);
>>> +
>>> +		if (mmc->caps2 & MMC_CAP2_BROKEN_VOLTAGE)
>>> +			min_uV = max_uV = voltage;
>>> +
>>>  		if (voltage < 0)
>>>  			result = voltage;
>>>  		else if (voltage < min_uV || voltage > max_uV)
>>> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
>>> index dd13e05..5659aee 100644
>>> --- a/include/linux/mmc/host.h
>>> +++ b/include/linux/mmc/host.h
>>> @@ -257,6 +257,7 @@ struct mmc_host {
>>>  #define MMC_CAP2_HS200_1_2V_SDR	(1 << 6)        /* can support */
>>>  #define MMC_CAP2_HS200		(MMC_CAP2_HS200_1_8V_SDR | \
>>>  				 MMC_CAP2_HS200_1_2V_SDR)
>>> +#define MMC_CAP2_BROKEN_VOLTAGE	(1 << 7)	/* Use the broken voltage */
>>>
>>>  	mmc_pm_flag_t		pm_caps;	/* supported pm features */
>>>  	unsigned int        power_notify_type;
>>> --
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>>
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>