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

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

On 17/01/12 11:53, Kyungmin Park wrote:
> On 1/17/12, Adrian Hunter <adrian.hunter@intel.com> wrote:
>> 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?
> Now 2.8V is supplied by gpio so make it fixed regulator
>> 	- is it supplying VCC or VCCQ?
> VDD in our schematic.

Is it the NAND core voltage or the I/O voltage?

>> 	- what is the contents of the OCR register?
> In sdhci_set_power(). it returns SDHCI_POWER_180, SDHCI_POWER_300, and
> SDHCI_POWER_330.
> In probe time, it return the SDHCI_POWER_330, and but fixed regulator
> returns the 2.8V so it calls regulator_set_voltage. and return -EINVAL
> since it's fixed regulator.
> 
> Of course we can make workaround, set fixed regulator voltage as 3.3V.
> Even though actual voltage is 2.8V. so it's ambiguous.
> 
> that's reason introduces the new quirk.
> 
> Thank you,
> Kyungmin Park
>>
>>> 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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>>>
>>
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>