Re: [PATCH V2 1/2] mmc: sdhci-msm: Add support to store supported vdd-io voltages

[Jeremy McNicoll]

On 2018-03-02 10:23 AM, Doug Anderson wrote:
> Hi,
>
> On Sun, Feb 11, 2018 at 10:01 PM, Vijay Viswanath
> <vviswana@xxxxxxxxxxxxxx> wrote:
> > During probe check whether the vdd-io regulator of sdhc platform device
> > can support 1.8V and 3V and store this information as a capability of
> > platform device.
> >
> > Signed-off-by: Vijay Viswanath <vviswana@xxxxxxxxxxxxxx>
> > ---
> >   drivers/mmc/host/sdhci-msm.c | 38 ++++++++++++++++++++++++++++++++++++++
> >   1 file changed, 38 insertions(+)
> >
> > diff --git a/drivers/mmc/host/sdhci-msm.c b/drivers/mmc/host/sdhci-msm.c
> > index c283291..5c23e92 100644
> > --- a/drivers/mmc/host/sdhci-msm.c
> > +++ b/drivers/mmc/host/sdhci-msm.c
> > @@ -23,6 +23,7 @@
> >   #include <linux/iopoll.h>
> >
> >   #include "sdhci-pltfm.h"
> > +#include <linux/regulator/consumer.h>
>
> This is a strange sort order for this include file.  Why is it after
> the local include?
>
>
> >   #define CORE_MCI_VERSION               0x50
> >   #define CORE_VERSION_MAJOR_SHIFT       28
> > @@ -81,6 +82,9 @@
> >   #define CORE_HC_SELECT_IN_HS400        (6 << 19)
> >   #define CORE_HC_SELECT_IN_MASK (7 << 19)
> >
> > +#define CORE_3_0V_SUPPORT      (1 << 25)
> > +#define CORE_1_8V_SUPPORT      (1 << 26)
> > +
>
> Is there something magical about 25 and 26?  This is a new caps field,
> so I'd have expected 0 and 1.
>
>
> >   #define CORE_CSR_CDC_CTLR_CFG0         0x130
> >   #define CORE_SW_TRIG_FULL_CALIB                BIT(16)
> >   #define CORE_HW_AUTOCAL_ENA            BIT(17)
> > @@ -148,6 +152,7 @@ struct sdhci_msm_host {
> >          u32 curr_io_level;
> >          wait_queue_head_t pwr_irq_wait;
> >          bool pwr_irq_flag;
> > +       u32 caps_0;
> >   };
> >
> >   static unsigned int msm_get_clock_rate_for_bus_mode(struct sdhci_host *host,
> > @@ -1313,6 +1318,35 @@ static void sdhci_msm_writeb(struct sdhci_host *host, u8 val, int reg)
> >                  sdhci_msm_check_power_status(host, req_type);
> >   }
> >
> > +static int sdhci_msm_set_regulator_caps(struct sdhci_msm_host *msm_host)
> > +{
> > +       struct mmc_host *mmc = msm_host->mmc;
> > +       struct regulator *supply = mmc->supply.vqmmc;
> > +       int i, count;
> > +       u32 caps = 0, vdd_uV;
> > +
> > +       if (!IS_ERR(mmc->supply.vqmmc)) {
> > +               count = regulator_count_voltages(supply);
> > +               if (count < 0)
> > +                       return count;
> > +               for (i = 0; i < count; i++) {
> > +                       vdd_uV = regulator_list_voltage(supply, i);
> > +                       if (vdd_uV <= 0)
> > +                               continue;
> > +                       if (vdd_uV > 2700000)
> > +                               caps |= CORE_3_0V_SUPPORT;
> > +                       if (vdd_uV < 1950000)
> > +                               caps |= CORE_1_8V_SUPPORT;
> > +               }
>
> Shouldn't you be using regulator_is_supported_voltage() rather than
> open coding?  Also: I've never personally worked on a device where it
> was used, but there is definitely a concept floating about of a
> voltage level of 1.2V.  Maybe should copy the ranges from
> mmc_regulator_set_vqmmc()?
>
>
> Also: seems like you should have some way to deal with "caps" ending
> up w/ no bits set.  IIRC you can have a regulator that can be enabled
> / disabled but doesn't list a voltage, so if someone messed up their
> device tree you could end up in this case.  Should you print a
> warning?  ...or treat it as if we support "3.0V"?  ...or ?  I guess it
> depends on how do you want patch #2 to behave in that case.

Both, initialize it to sane value and print something.  This way at
least you have a good chance of booting and not hard hanging and you
are given a reasonable message indicating what needs to be fixed.

-jeremy

> > +       }
>
> How should things behave if vqmmc is an error?  In that case is it
> important to not set "CORE_IO_PAD_PWR_SWITCH_EN" in patch set #2?
> ...or should you set "CORE_IO_PAD_PWR_SWITCH_EN" but then make sure
> you don't set "CORE_IO_PAD_PWR_SWITCH"?
>
>
> > +       msm_host->caps_0 |= caps;
> > +       pr_debug("%s: %s: supported caps: 0x%08x\n", mmc_hostname(mmc),
> > +                       __func__, caps);
> > +
> > +       return 0;
> > +}
> > +
> > +
> >   static const struct of_device_id sdhci_msm_dt_match[] = {
> >          { .compatible = "qcom,sdhci-msm-v4" },
> >          {},
> > @@ -1530,6 +1564,10 @@ static int sdhci_msm_probe(struct platform_device *pdev)
> >          ret = sdhci_add_host(host);
> >          if (ret)
> >                  goto pm_runtime_disable;
> > +       ret = sdhci_msm_set_regulator_caps(msm_host);
> > +       if (ret)
> > +               dev_err(&pdev->dev, "%s: Failed to set regulator caps: %d\n",
> > +                               __func__, ret);
>
> Why do you need __func__ here?  You're already using dev_err(), that
> gives an idea of where we are.
>
>
> >          pm_runtime_mark_last_busy(&pdev->dev);
> >          pm_runtime_put_autosuspend(&pdev->dev);
> > --
> >   Qualcomm India Private Limited, on behalf of Qualcomm Innovation Center, Inc.
> > Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project.
> >
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