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

[Adrian Hunter]

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@xxxxxxxxxxxxxx>
>>>>> ---
>>>>> ÂÂ drivers/mmc/host/sdhci.c | 20 +++++++++++++++-----
>>>>> ÂÂ drivers/mmc/host/sdhci.h |Â 2 ++
>>>>> ÂÂ 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,
>>>>> ÂÂ void sdhci_set_power(struct sdhci_host *host, unsigned char mode,
>>>>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ unsigned short vdd)
>>>>> ÂÂ {
>>>>> -ÂÂÂ if (IS_ERR(host->mmc->supply.vmmc))
>>>>> +ÂÂÂ if (IS_ERR(host->mmc->supply.vmmc) ||
>>>>> +ÂÂÂÂÂÂÂÂÂÂÂ (host->quirks2 & SDHCI_QUIRK2_INTERNAL_PWR_CTL))
>>>>
>>>> I think you should provide your own ->set_power() instead of this
>>>>
>>>
>>> will do
>>>
>>>>> ÂÂÂÂÂÂÂÂÂÂ sdhci_set_power_noreg(host, mode, vdd);
>>>>> ÂÂÂÂÂÂ else
>>>>> ÂÂÂÂÂÂÂÂÂÂ sdhci_set_power_reg(host, mode, vdd);
>>>>> @@ -2009,7 +2010,9 @@ int sdhci_start_signal_voltage_switch(struct
>>>>> mmc_host *mmc,
>>>>> ÂÂÂÂÂÂÂÂÂÂ ctrl &= ~SDHCI_CTRL_VDD_180;
>>>>> ÂÂÂÂÂÂÂÂÂÂ sdhci_writew(host, ctrl, SDHCI_HOST_CONTROL2);
>>>>> ÂÂ -ÂÂÂÂÂÂÂ if (!IS_ERR(mmc->supply.vqmmc)) {
>>>>> +ÂÂÂÂÂÂÂ if (!IS_ERR(mmc->supply.vqmmc) &&
>>>>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ !(host->quirks2 &
>>>>> +ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ 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.
>>>
>>>>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ ret = mmc_regulator_set_vqmmc(mmc, ios);
>>>>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ if (ret) {
>>>>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ 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,
>>>>> ÂÂÂÂÂÂ case MMC_SIGNAL_VOLTAGE_180:
>>>>> ÂÂÂÂÂÂÂÂÂÂ if (!(host->flags & SDHCI_SIGNALING_180))
>>>>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ return -EINVAL;
>>>>> -ÂÂÂÂÂÂÂ if (!IS_ERR(mmc->supply.vqmmc)) {
>>>>> +ÂÂÂÂÂÂÂ if (!IS_ERR(mmc->supply.vqmmc) &&
>>>>> +ÂÂÂÂÂÂÂÂÂÂÂ !(host->quirks2 & SDHCI_QUIRK2_INTERNAL_PWR_CTL)) {
>>>>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ ret = mmc_regulator_set_vqmmc(mmc, ios);
>>>>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ if (ret) {
>>>>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ pr_warn("%s: Switching to 1.8V signalling voltage
>>>>> failed\n",
>>>>> @@ -3485,7 +3489,10 @@ int sdhci_setup_host(struct sdhci_host *host)
>>>>> ÂÂÂÂÂÂÂ * the host can take the appropriate action if regulators are not
>>>>> ÂÂÂÂÂÂÂ * available.
>>>>> ÂÂÂÂÂÂÂ */
>>>>> -ÂÂÂ ret = mmc_regulator_get_supply(mmc);
>>>>> +ÂÂÂ if (!(host->quirks2 & SDHCI_QUIRK2_INTERNAL_PWR_CTL))
>>>>
>>>> Since we expect mmc_regulator_get_supply() to have been called, this could
>>>> be:
>>>>
>>>> ÂÂÂÂÂif (!mmc->supply.vmmc) {
>>>> ÂÂÂÂÂÂÂÂ ret = mmc_regulator_get_supply(mmc);
>>>> ÂÂÂÂÂÂÂÂ enable_vqmmc = true;
>>>> ÂÂÂÂÂ} else {
>>>> ÂÂÂÂÂÂÂÂ ret = 0;
>>>> ÂÂÂÂÂ}
>>>>>> +ÂÂÂÂÂÂÂ ret = mmc_regulator_get_supply(mmc);
>>>>> +ÂÂÂ else
>>>>> +ÂÂÂÂÂÂÂ ret = 0;
>>>>> ÂÂÂÂÂÂ if (ret)
>>>>> ÂÂÂÂÂÂÂÂÂÂ return ret;
>>>>> ÂÂ @@ -3736,7 +3743,10 @@ int sdhci_setup_host(struct sdhci_host *host)
>>>>> ÂÂ ÂÂÂÂÂ /* If vqmmc regulator and no 1.8V signalling, then there's no
>>>>> UHS */
>>>>> ÂÂÂÂÂÂ if (!IS_ERR(mmc->supply.vqmmc)) {
>>>>> -ÂÂÂÂÂÂÂ ret = regulator_enable(mmc->supply.vqmmc);
>>>>> +ÂÂÂÂÂÂÂ if (!(host->quirks2 & SDHCI_QUIRK2_INTERNAL_PWR_CTL))
>>>>
>>>> And this could be:
>>>>
>>>> ÂÂÂÂÂÂÂÂ if (enable_vqmmc)
>>>> ÂÂÂÂÂÂÂÂÂÂÂÂ ret = regulator_enable(mmc->supply.vqmmc);
>>>> ÂÂÂÂÂÂÂÂ else
>>>> ÂÂÂÂÂÂÂÂÂÂÂÂ ret = 0;
>>>> ÂÂ> 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.
>>
>> ÂÂÂÂif (host->vqmmc_enabled)
>> ÂÂÂÂÂÂÂ regulator_disable(mmc->supply.vqmmc);
>>
> 
> Ok, so we will be adding a new flag "vqmmc_enabled" in sdhci_host, ryt ?

Yes

> 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.
>>
>>>>
>>>>> +ÂÂÂÂÂÂÂÂÂÂÂ ret = regulator_enable(mmc->supply.vqmmc);
>>>>> +ÂÂÂÂÂÂÂ else
>>>>> +ÂÂÂÂÂÂÂÂÂÂÂ ret = 0;
>>>>> ÂÂÂÂÂÂÂÂÂÂ if (!regulator_is_supported_voltage(mmc->supply.vqmmc, 1700000,
>>>>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ 1950000))
>>>>> ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ 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 {
>>>>> ÂÂÂ * obtainable timeout.
>>>>> ÂÂÂ */
>>>>> ÂÂ #define SDHCI_QUIRK2_DISABLE_HW_TIMEOUTÂÂÂÂÂÂÂÂÂÂÂ (1<<17)
>>>>> +/* Regulator voltage changes are being done from platform layer */
>>>>> +#define SDHCI_QUIRK2_INTERNAL_PWR_CTLÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ (1<<18)
>>>>
>>>> So maybe the quirk is not needed.
>>>>
>>>>> ÂÂ ÂÂÂÂÂ int irq;ÂÂÂÂÂÂÂ /* Device IRQ */
>>>>> ÂÂÂÂÂÂ void __iomem *ioaddr;ÂÂÂ /* Mapped address */
>>>>>
>>>>
>>>
>>> Thanks for the review & suggestions!
>>> Vijay
>>>
>>
>