Re: [PATCH V4 2/2] mmc: sdhci-msm: Use internal voltage control

[Ulf Hansson]

On Wed, 17 Jun 2020 at 14:46, Veerabhadrarao Badiganti
<vbadigan@xxxxxxxxxxxxxx> wrote:
>
> Thanks for comments Uffe.
>
> On 6/17/2020 3:04 PM, Ulf Hansson wrote:
> > On Tue, 16 Jun 2020 at 17:38, Veerabhadrarao Badiganti
> > <vbadigan@xxxxxxxxxxxxxx> wrote:
> >> On qcom SD host controllers voltage switching be done after the HW
> >> is ready for it. The HW informs its readiness through power irq.
> >> The voltage switching should happen only then.
> >>
> >> Use the internal voltage switching and then control the voltage
> >> switching using power irq.
> >>
> >> IO-bus supply of eMMC would be kept always-on. So set the load
> >> for this supply to configure it in LPM when eMMC is suspend state
> >>   and in HPM when eMMC is active.
> >>
> >> Co-developed-by: Asutosh Das <asutoshd@xxxxxxxxxxxxxx>
> >> Signed-off-by: Asutosh Das <asutoshd@xxxxxxxxxxxxxx>
> >> Co-developed-by: Vijay Viswanath <vviswana@xxxxxxxxxxxxxx>
> >> Signed-off-by: Vijay Viswanath <vviswana@xxxxxxxxxxxxxx>
> >> Co-developed-by: Veerabhadrarao Badiganti <vbadigan@xxxxxxxxxxxxxx>
> >> Signed-off-by: Veerabhadrarao Badiganti <vbadigan@xxxxxxxxxxxxxx>
> >> ---
> >>   drivers/mmc/host/sdhci-msm.c | 208 +++++++++++++++++++++++++++++++++++++++++--
> >>   1 file changed, 199 insertions(+), 9 deletions(-)
> >>
> >> diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
> >> index 15c42b059240..8297b2142748 100644
> >> --- a/drivers/mmc/host/sdhci-msm.c
> >> +++ b/drivers/mmc/host/sdhci-msm.c
> >> @@ -37,7 +37,9 @@
> >>   #define CORE_PWRCTL_IO_LOW     BIT(2)
> >>   #define CORE_PWRCTL_IO_HIGH    BIT(3)
> >>   #define CORE_PWRCTL_BUS_SUCCESS BIT(0)
> >> +#define CORE_PWRCTL_BUS_FAIL    BIT(1)
> >>   #define CORE_PWRCTL_IO_SUCCESS BIT(2)
> >> +#define CORE_PWRCTL_IO_FAIL     BIT(3)
> >>   #define REQ_BUS_OFF            BIT(0)
> >>   #define REQ_BUS_ON             BIT(1)
> >>   #define REQ_IO_LOW             BIT(2)
> >> @@ -127,6 +129,9 @@
> >>   /* Timeout value to avoid infinite waiting for pwr_irq */
> >>   #define MSM_PWR_IRQ_TIMEOUT_MS 5000
> >>
> >> +/* Max load for eMMC Vdd-io supply */
> >> +#define MMC_VQMMC_MAX_LOAD_UA  325000
> >> +
> >>   #define msm_host_readl(msm_host, host, offset) \
> >>          msm_host->var_ops->msm_readl_relaxed(host, offset)
> >>
> >> @@ -278,6 +283,7 @@ struct sdhci_msm_host {
> >>          bool uses_tassadar_dll;
> >>          u32 dll_config;
> >>          u32 ddr_config;
> >> +       bool vqmmc_enabled;
> >>   };
> >>
> >>   static const struct sdhci_msm_offset *sdhci_priv_msm_offset(struct sdhci_host *host)
> >> @@ -1346,6 +1352,88 @@ static void sdhci_msm_set_uhs_signaling(struct sdhci_host *host,
> >>                  sdhci_msm_hs400(host, &mmc->ios);
> >>   }
> >>
> >> +static int sdhci_msm_set_vmmc(struct mmc_host *mmc)
> >> +{
> >> +       if (IS_ERR(mmc->supply.vmmc))
> >> +               return 0;
> >> +
> >> +       return mmc_regulator_set_ocr(mmc, mmc->supply.vmmc, mmc->ios.vdd);
> >> +}
> >> +
> >> +static int msm_toggle_vqmmc(struct sdhci_msm_host *msm_host,
> >> +                             struct mmc_host *mmc, bool level)
> >> +{
> >> +       int ret;
> >> +       struct mmc_ios ios;
> >> +
> >> +       if (msm_host->vqmmc_enabled == level)
> >> +               return 0;
> >> +
> >> +       if (level) {
> >> +               /* Set the IO voltage regulator to default voltage level */
> >> +               if (msm_host->caps_0 & CORE_3_0V_SUPPORT)
> >> +                       ios.signal_voltage = MMC_SIGNAL_VOLTAGE_330;
> >> +               else if (msm_host->caps_0 & CORE_1_8V_SUPPORT)
> >> +                       ios.signal_voltage = MMC_SIGNAL_VOLTAGE_180;
> >> +
> >> +               if (msm_host->caps_0 & CORE_VOLT_SUPPORT) {
> >> +                       ret = mmc_regulator_set_vqmmc(mmc, &ios);
> >> +                       if (ret < 0) {
> >> +                               dev_err(mmc_dev(mmc), "%s: vqmmc set volgate failed: %d\n",
> >> +                                       mmc_hostname(mmc), ret);
> >> +                               goto out;
> >> +                       }
> >> +               }
> >> +               ret = regulator_enable(mmc->supply.vqmmc);
> >> +       } else {
> >> +               ret = regulator_disable(mmc->supply.vqmmc);
> >> +       }
> >> +
> >> +       if (ret)
> >> +               dev_err(mmc_dev(mmc), "%s: vqmm %sable failed: %d\n",
> >> +                       mmc_hostname(mmc), level ? "en":"dis", ret);
> >> +       else
> >> +               msm_host->vqmmc_enabled = level;
> >> +out:
> >> +       return ret;
> >> +}
> >> +
> >> +static int msm_config_vqmmc_mode(struct sdhci_msm_host *msm_host,
> >> +                             struct mmc_host *mmc, bool hpm)
> >> +{
> >> +       int load, ret;
> >> +
> >> +       load = hpm ? MMC_VQMMC_MAX_LOAD_UA : 0;
> >> +       ret = regulator_set_load(mmc->supply.vqmmc, load);
> >> +       if (ret)
> >> +               dev_err(mmc_dev(mmc), "%s: vqmmc set load failed: %d\n",
> >> +                       mmc_hostname(mmc), ret);
> >> +       return ret;
> >> +}
> >> +
> >> +static int sdhci_msm_set_vqmmc(struct sdhci_msm_host *msm_host,
> >> +                             struct mmc_host *mmc, bool level)
> >> +{
> >> +       int ret;
> >> +       bool always_on;
> >> +
> >> +       if (IS_ERR(mmc->supply.vqmmc)           ||
> > White space.
> >
> >> +           (mmc->ios.power_mode == MMC_POWER_UNDEFINED))
> >> +               return 0;
> >> +       /*
> >> +        * For eMMC don't turn off Vqmmc, Instead just configure it in LPM
> >> +        * and HPM modes by setting the right amonut of load.
> > /s/right amonut of load/corresponding load
> >
> >> +        */
> >> +       always_on = mmc->card && mmc_card_mmc(mmc->card);
> >> +
> >> +       if (always_on)
> >> +               ret = msm_config_vqmmc_mode(msm_host, mmc, level);
> >> +       else
> >> +               ret = msm_toggle_vqmmc(msm_host, mmc, level);
> > I am worried that this isn't really doing what you think it does.
> > always_on may not always be set for an eMMC.
> >
> > This is because the mmc->card doesn't get assigned until the
> > initialization of the eMMC has been completed. In other words, way
> > after VCC and VCCQ have been turned on and changed voltage levels.
> For the very first time, i have to enable the vqmmc.
> And second time on-wards I have to set load instead of turning vqmmc off
> / on.
>
> This condition helps me in doing exactly the same.
>
> This gets invoked first time when  mmc_power_up() is called.
> Yes, by that time card won't be initialized. So this check fails and
> allows to turn on the regulator instead of setting load.
>
> After that, this gets invoked only next time mmc_power_up/off() is called
> which is during mmc_suspend/resume.

I see.

That assumes the initialization always works at the first attempt, so
no re-try or power cycle gets done in some error/reset path.

>
> By this time card is initialized, it allows to set load.

Okay, I get it. Thanks for clarifying.

Perhaps you can add a small comment about this in the code, so we
don't forget the reasons why the code looks like this.

>
>
> > Moreover, mmc_card_mmc() is also about legacy MMC cards, not solely for eMMCs.
>
> Okay. But on qcom platform, we have support for only eMMC/SD/SDIO.
> So this mmc_card_mmc() meets my requirements!!! Allows only eMMC not SD
> & SDIO.

Well, eMMC is fairly similar to MMC, from a basic functionality point
of view. So, I am quite sure you can get it to work with your
controller, even if it's not officially supported.

>
> > If you want special treatment of an eMMC, I think it's better to use
> > the DT bindings Documentation/devicetree/bindings/mmc/mmc-card.txt. If
> > you have such a subnode, that indicates that there is an eMMC card
> > attached.

That said, if you don't like the pure DT based solution, as I
suggested above - at least extend mmc_card_mmc() with checking the
MMC_CAP_NONREMOVABLE flag.

[...]

Kind regards
Uffe