On 4 April 2013 11:44, Prasanna NAVARATNA <prasanna.navaratna@xxxxxxxxx> wrote:
> Kevin Liu <kliu5 <at> marvell.com> writes:
>
>>
>> host->ocr has been reset in power off but not restored after power up
>> in resume. And operation voltage will be set to the highest after resume
>> back. This patch fix these two bugs.
>>
>> Signed-off-by: Kevin Liu <kliu5 <at> marvell.com>
>> ---
>> drivers/mmc/core/core.c | 3 ++-
>> include/linux/mmc/host.h | 1 +
>> 2 files changed, 3 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/mmc/core/core.c b/drivers/mmc/core/core.c
>> index 08a3cf2..b8c3d41 100644
>> --- a/drivers/mmc/core/core.c
>> +++ b/drivers/mmc/core/core.c
>> <at> <at> -1523,6 +1523,7 <at> <at> void mmc_power_off(struct
> mmc_host *host)
>> * Reset ocr mask to be the highest possible voltage supported for
>> * this mmc host. This value will be used at next power up.
>> */
>> + host->ocr_bak = host->ocr;
>> host->ocr = 1 << (fls(host->ocr_avail) - 1);
>>
>> if (!mmc_host_is_spi(host)) {
>> <at> <at> -2666,7 +2667,7 <at> <at> int mmc_resume_host(struct
> mmc_host *host)
>> if (host->bus_ops && !host->bus_dead) {
>> if (!mmc_card_keep_power(host)) {
>> mmc_power_up(host);
>> - mmc_select_voltage(host, host->ocr);
>> + host->ocr = mmc_select_voltage(host, host->ocr_bak);
>> /*
>> * Tell runtime PM core we just powered up the card,
>> * since it still believes the card is powered off.
>> diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
>> index d6f20cc..6e355d1 100644
>> --- a/include/linux/mmc/host.h
>> +++ b/include/linux/mmc/host.h
>> <at> <at> -309,6 +309,7 <at> <at> struct mmc_host {
>>
>> struct mmc_ios ios; /* current io bus settings
> */
>> u32 ocr; /* the current OCR setting
> */
>> + u32 ocr_bak; /* save current OCR setting
> */
>>
>> /* group bitfields together to minimize padding */
>> unsigned int use_spi_crc:1;
>
>
> Hello Kevin,
>
> Any update on this patch?
>
> I have seen an issue where during initialization, core will get card's ocr
> and match with host ocr available and select the appropriate voltage (3.0V)
You may think this is done correct, but it is not. Host drivers does
in general not change voltage in MMC_POWER_ON state, which is what is
required if the new negotiated ocr mask shall be used. According to
the mmc/sd spec voltage level changes requires a full power cycle
sequence which is not done from the protocol layer, and which is why
host drivers also should not consider changing voltages at
MMC_POWER_ON state.
Note that debugfs is then also not telling the truth about the voltage
level being used.
> But during suspend, maximum supported voltage from host is saved back and
> when resuming back requesting for highest voltage of host (3.3V).
> It doesn't care about card's OCR.
In practice, it is same voltage level that has been used all the time,
except for those host driver that do change levels in MMC_POWER_ON
mode.
Kind regards
Ulf Hansson
>
> This patch fixes it. Looks valid for me.
>
> Thanks & Regards,
> Prasanna NAVARATNA
>
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