Re: [PATCH RFC 1/2] mmc: sdhci: Allow platform controlled voltage switching

[Vijay Viswanath <vviswana@codeaurora.org>]

On 7/17/2018 3:24 PM, Adrian Hunter wrote:
> On 17/07/18 12:45, Vijay Viswanath wrote:
>>
>>
>> On 7/17/2018 2:12 PM, Adrian Hunter wrote:
>>> On 17/07/18 11:40, Vijay Viswanath wrote:
>>>>
>>>>
>>>> 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 ?
>>>
>>> Yes
>>>
>>
>> Ok.
>> Any particular reason why we are avoiding quirk and instead adding a new flag ?
> 
> It moves more in the direction of letting drivers do what they want, rather
> than trying to make making SDHCI do everything.
> 

ok will incorporate the changes in next version.

>>
>>>> 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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>>
> 

Thanks,
Vijay