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

[Kyungmin Park <kyungmin.park@samsung.com>]

On 1/17/12, Adrian Hunter <adrian.hunter@intel.com> wrote:
> 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?
In case of eMMC v4.41, it uses the same voltage, VDD is used for MMC
I/O block and controller and another VDDF is used for flash.
>
>>> 	- 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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>>
>
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