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Message-ID: <82109d4a-6e3c-eb80-6843-75bf7c89c113@intel.com>
Date: Tue, 17 Jul 2018 12:54:43 +0300
From: Adrian Hunter <adrian.hunter@...el.com>
To: Vijay Viswanath <vviswana@...eaurora.org>, 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 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@...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 ?
>>
>> 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.
>
>>> 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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>>
>
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