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Date: Tue, 17 Jul 2018 14:10:21 +0530
From: Vijay Viswanath <vviswana@...eaurora.org>
To: Adrian Hunter <adrian.hunter@...el.com>, ulf.hansson@...aro.org,
robh+dt@...nel.org, mark.rutland@....com
Cc: linux-mmc@...r.kernel.org, linux-kernel@...r.kernel.org,
shawn.lin@...k-chips.com, linux-arm-msm@...r.kernel.org,
georgi.djakov@...aro.org, devicetree@...r.kernel.org,
asutoshd@...eaurora.org, stummala@...eaurora.org,
venkatg@...eaurora.org, jeremymc@...hat.com,
bjorn.andersson@...aro.org, riteshh@...eaurora.org,
vbadigan@...eaurora.org, dianders@...gle.com,
sayalil@...eaurora.org, Evan Green <evgreen@...omium.org>
Subject: Re: [PATCH RFC 1/2] mmc: sdhci: Allow platform controlled voltage
switching
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@...eaurora.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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