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SubjectRe: [PATCH RFC 1/2] mmc: sdhci: Allow platform controlled voltage switching
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On 7/17/2018 1:00 PM, Adrian Hunter wrote:
> On 17/07/18 08:14, Vijay Viswanath wrote:
>>
>>
>> On 7/10/2018 4:37 PM, Adrian Hunter wrote:
>>> On 21/06/18 15:23, Vijay Viswanath wrote:
>>>> Some controllers can have internal mechanism to inform the SW that it
>>>> is ready for voltage switching. For such controllers, changing voltage
>>>> before the HW is ready can result in various issues.
>>>>
>>>> Add a quirk, which can be used by drivers of such controllers.
>>>>
>>>> Signed-off-by: Vijay Viswanath <vviswana@codeaurora.org>
>>>> ---
>>>>   drivers/mmc/host/sdhci.c | 20 +++++++++++++++-----
>>>>   drivers/mmc/host/sdhci.h |  2 ++
>>>>   2 files changed, 17 insertions(+), 5 deletions(-)
>>>>
>>>> diff --git a/drivers/mmc/host/sdhci.c b/drivers/mmc/host/sdhci.c
>>>> index 1c828e0..f0346d4 100644
>>>> --- a/drivers/mmc/host/sdhci.c
>>>> +++ b/drivers/mmc/host/sdhci.c
>>>> @@ -1615,7 +1615,8 @@ void sdhci_set_power_noreg(struct sdhci_host *host,
>>>> unsigned char mode,
>>>>   void sdhci_set_power(struct sdhci_host *host, unsigned char mode,
>>>>                unsigned short vdd)
>>>>   {
>>>> -    if (IS_ERR(host->mmc->supply.vmmc))
>>>> +    if (IS_ERR(host->mmc->supply.vmmc) ||
>>>> +            (host->quirks2 & SDHCI_QUIRK2_INTERNAL_PWR_CTL))
>>>
>>> I think you should provide your own ->set_power() instead of this
>>>
>>
>> will do
>>
>>>>           sdhci_set_power_noreg(host, mode, vdd);
>>>>       else
>>>>           sdhci_set_power_reg(host, mode, vdd);
>>>> @@ -2009,7 +2010,9 @@ int sdhci_start_signal_voltage_switch(struct
>>>> mmc_host *mmc,
>>>>           ctrl &= ~SDHCI_CTRL_VDD_180;
>>>>           sdhci_writew(host, ctrl, SDHCI_HOST_CONTROL2);
>>>>   -        if (!IS_ERR(mmc->supply.vqmmc)) {
>>>> +        if (!IS_ERR(mmc->supply.vqmmc) &&
>>>> +                !(host->quirks2 &
>>>> +                    SDHCI_QUIRK2_INTERNAL_PWR_CTL)) {
>>>
>>> And your own ->start_signal_voltage_switch()
>>>
>>
>> sdhci_msm_start_signal_voltage_switch() would be an exact copy of
>> sdhci_start_signal_voltage_switch()..... will incorporate this if not using
>> quirk.
>>
>>>>               ret = mmc_regulator_set_vqmmc(mmc, ios);
>>>>               if (ret) {
>>>>                   pr_warn("%s: Switching to 3.3V signalling voltage
>>>> failed\n",
>>>> @@ -2032,7 +2035,8 @@ int sdhci_start_signal_voltage_switch(struct
>>>> mmc_host *mmc,
>>>>       case MMC_SIGNAL_VOLTAGE_180:
>>>>           if (!(host->flags & SDHCI_SIGNALING_180))
>>>>               return -EINVAL;
>>>> -        if (!IS_ERR(mmc->supply.vqmmc)) {
>>>> +        if (!IS_ERR(mmc->supply.vqmmc) &&
>>>> +            !(host->quirks2 & SDHCI_QUIRK2_INTERNAL_PWR_CTL)) {
>>>>               ret = mmc_regulator_set_vqmmc(mmc, ios);
>>>>               if (ret) {
>>>>                   pr_warn("%s: Switching to 1.8V signalling voltage
>>>> failed\n",
>>>> @@ -3485,7 +3489,10 @@ int sdhci_setup_host(struct sdhci_host *host)
>>>>        * the host can take the appropriate action if regulators are not
>>>>        * available.
>>>>        */
>>>> -    ret = mmc_regulator_get_supply(mmc);
>>>> +    if (!(host->quirks2 & SDHCI_QUIRK2_INTERNAL_PWR_CTL))
>>>
>>> Since we expect mmc_regulator_get_supply() to have been called, this could
>>> be:
>>>
>>>     if (!mmc->supply.vmmc) {
>>>         ret = mmc_regulator_get_supply(mmc);
>>>         enable_vqmmc = true;
>>>     } else {
>>>         ret = 0;
>>>     }
>>>>> +        ret = mmc_regulator_get_supply(mmc);
>>>> +    else
>>>> +        ret = 0;
>>>>       if (ret)
>>>>           return ret;
>>>>   @@ -3736,7 +3743,10 @@ int sdhci_setup_host(struct sdhci_host *host)
>>>>         /* If vqmmc regulator and no 1.8V signalling, then there's no UHS */
>>>>       if (!IS_ERR(mmc->supply.vqmmc)) {
>>>> -        ret = regulator_enable(mmc->supply.vqmmc);
>>>> +        if (!(host->quirks2 & SDHCI_QUIRK2_INTERNAL_PWR_CTL))
>>>
>>> And this could be:
>>>
>>>         if (enable_vqmmc)
>>>             ret = regulator_enable(mmc->supply.vqmmc);
>>>         else
>>>             ret = 0;
>>>  > However, you still need to ensure regulator_disable(mmc->supply.vqmmc) is
>>> only called if regulator_enable() was called.
>> I missed this. Will cover it.
>>
>> Also I missed one more place where we are doing regulator_disable. During
>> sdhci-msm unbinding, we would end up doing an extra regulator disable
>> (thanks Evan for pointing it out) in sdhci_remove_host.
>>
>> To avoid the quirk( or having any flag), it would require copying the code
>> of sdhci_start_signal_voltage_switch() and sdhci_remove_host() and creating
>
> You do not need to duplicate sdhci_remove_host(), just change it so that it
> only disables what was enabled i.e.
>
> if (host->vqmmc_enabled)
> regulator_disable(mmc->supply.vqmmc);
>

Ok, so we will be adding a new flag "vqmmc_enabled" in sdhci_host, ryt ?
Just wanted to clarify

>> 2 new functions in sdhci_msm layer which would do the exact same as above,
>> with just the regulator parts removed.
>>
>> This looks messy (considering any future changes to the 2 sdhci API will
>> need to be copied to their duplicate sdhci_msm API) and a bit overkill to
>> avoid quirk. At the same time, I don't know how useful such a quirk would be
>> to other platform drivers.
>>
>> Please let me know your view/suggestions.
>
> Let's try without the quirk.
>
>>>
>>>> +            ret = regulator_enable(mmc->supply.vqmmc);
>>>> +        else
>>>> +            ret = 0;
>>>>           if (!regulator_is_supported_voltage(mmc->supply.vqmmc, 1700000,
>>>>                               1950000))
>>>>               host->caps1 &= ~(SDHCI_SUPPORT_SDR104 |
>>>> diff --git a/drivers/mmc/host/sdhci.h b/drivers/mmc/host/sdhci.h
>>>> index 23966f8..3b0c97a 100644
>>>> --- a/drivers/mmc/host/sdhci.h
>>>> +++ b/drivers/mmc/host/sdhci.h
>>>> @@ -450,6 +450,8 @@ struct sdhci_host {
>>>>    * obtainable timeout.
>>>>    */
>>>>   #define SDHCI_QUIRK2_DISABLE_HW_TIMEOUT            (1<<17)
>>>> +/* Regulator voltage changes are being done from platform layer */
>>>> +#define SDHCI_QUIRK2_INTERNAL_PWR_CTL                (1<<18)
>>>
>>> So maybe the quirk is not needed.
>>>
>>>>         int irq;        /* Device IRQ */
>>>>       void __iomem *ioaddr;    /* Mapped address */
>>>>
>>>
>>
>> Thanks for the review & suggestions!
>> Vijay
>>
>

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