Re: [PATCH 3/9] regulator: mt6358: Merge VCN33_* regulators

[Chen-Yu Tsai]

On Fri, Jun 9, 2023 at 4:58 PM AngeloGioacchino Del Regno
<angelogioacchino.delregno@xxxxxxxxxxxxx> wrote:
>
> Il 09/06/23 10:30, Chen-Yu Tsai ha scritto:
> > The VCN33_BT and VCN33_WIFI regulators are actually the same regulator,
> > having the same voltage setting and output pin. There are simply two
> > enable bits that are ORed together to enable the regulator.
> >
> > Having two regulators representing the same output pin is misleading
> > from a design matching standpoint, and also error-prone in driver
> > implementations. If consumers try to set different voltages on either
> > regulator, the one set later would override the one set before. There
> > are ways around this, such as chaining them together and having the
> > downstream one act as a switch. But given there's only one output pin,
> > such a workaround doesn't match reality.
> >
> > Remove the VCN33_WIFI regulator. During the probe phase, have the driver
> > sync the enable status of VCN33_WIFI to VCN33_BT. Also drop the suffix
> > so that the regulator name matches the pin name in the datasheet.
> >
> > Signed-off-by: Chen-Yu Tsai <wenst@xxxxxxxxxxxx>
> > ---
> >   drivers/regulator/mt6358-regulator.c       | 65 +++++++++++++++++-----
> >   include/linux/regulator/mt6358-regulator.h |  6 +-
> >   2 files changed, 52 insertions(+), 19 deletions(-)
> >
> > diff --git a/drivers/regulator/mt6358-regulator.c b/drivers/regulator/mt6358-regulator.c
> > index c9e16bd092f6..faf6b0757019 100644
> > --- a/drivers/regulator/mt6358-regulator.c
> > +++ b/drivers/regulator/mt6358-regulator.c
> > @@ -277,7 +277,7 @@ static const unsigned int vcama_voltages[] = {
> >       2800000, 2900000, 3000000,
> >   };
> >
> > -static const unsigned int vcn33_bt_wifi_voltages[] = {
> > +static const unsigned int vcn33_voltages[] = {
> >       3300000, 3400000, 3500000,
> >   };
> >
> > @@ -321,7 +321,7 @@ static const u32 vcama_idx[] = {
> >       0, 7, 9, 10, 11, 12,
> >   };
> >
> > -static const u32 vcn33_bt_wifi_idx[] = {
> > +static const u32 vcn33_idx[] = {
> >       1, 2, 3,
> >   };
> >
> > @@ -566,12 +566,8 @@ static struct mt6358_regulator_info mt6358_regulators[] = {
> >                  MT6358_LDO_VCAMA1_CON0, 0, MT6358_VCAMA1_ANA_CON0, 0xf00),
> >       MT6358_LDO("ldo_vemc", VEMC, vmch_vemc_voltages, vmch_vemc_idx,
> >                  MT6358_LDO_VEMC_CON0, 0, MT6358_VEMC_ANA_CON0, 0x700),
> > -     MT6358_LDO("ldo_vcn33_bt", VCN33_BT, vcn33_bt_wifi_voltages,
> > -                vcn33_bt_wifi_idx, MT6358_LDO_VCN33_CON0_0,
> > -                0, MT6358_VCN33_ANA_CON0, 0x300),
> > -     MT6358_LDO("ldo_vcn33_wifi", VCN33_WIFI, vcn33_bt_wifi_voltages,
> > -                vcn33_bt_wifi_idx, MT6358_LDO_VCN33_CON0_1,
> > -                0, MT6358_VCN33_ANA_CON0, 0x300),
> > +     MT6358_LDO("ldo_vcn33", VCN33, vcn33_voltages, vcn33_idx,
> > +                MT6358_LDO_VCN33_CON0_0, 0, MT6358_VCN33_ANA_CON0, 0x300),
> >       MT6358_LDO("ldo_vcama2", VCAMA2, vcama_voltages, vcama_idx,
> >                  MT6358_LDO_VCAMA2_CON0, 0, MT6358_VCAMA2_ANA_CON0, 0xf00),
> >       MT6358_LDO("ldo_vmc", VMC, vmc_voltages, vmc_idx,
> > @@ -662,12 +658,8 @@ static struct mt6358_regulator_info mt6366_regulators[] = {
> >                  MT6358_LDO_VMCH_CON0, 0, MT6358_VMCH_ANA_CON0, 0x700),
> >       MT6366_LDO("ldo_vemc", VEMC, vmch_vemc_voltages, vmch_vemc_idx,
> >                  MT6358_LDO_VEMC_CON0, 0, MT6358_VEMC_ANA_CON0, 0x700),
> > -     MT6366_LDO("ldo_vcn33_bt", VCN33_BT, vcn33_bt_wifi_voltages,
> > -                vcn33_bt_wifi_idx, MT6358_LDO_VCN33_CON0_0,
> > -                0, MT6358_VCN33_ANA_CON0, 0x300),
> > -     MT6366_LDO("ldo_vcn33_wifi", VCN33_WIFI, vcn33_bt_wifi_voltages,
> > -                vcn33_bt_wifi_idx, MT6358_LDO_VCN33_CON0_1,
> > -                0, MT6358_VCN33_ANA_CON0, 0x300),
> > +     MT6366_LDO("ldo_vcn33", VCN33, vcn33_voltages, vcn33_idx,
> > +                MT6358_LDO_VCN33_CON0_0, 0, MT6358_VCN33_ANA_CON0, 0x300),
> >       MT6366_LDO("ldo_vmc", VMC, vmc_voltages, vmc_idx,
> >                  MT6358_LDO_VMC_CON0, 0, MT6358_VMC_ANA_CON0, 0xf00),
> >       MT6366_LDO("ldo_vsim2", VSIM2, vsim_voltages, vsim_idx,
> > @@ -690,13 +682,56 @@ static struct mt6358_regulator_info mt6366_regulators[] = {
> >                   MT6358_LDO_VSRAM_CON1, 0x7f),
> >   };
> >
> > +static int mt6358_sync_vcn33_setting(struct device *dev)
> > +{
> > +     struct mt6397_chip *mt6397 = dev_get_drvdata(dev->parent);
> > +     unsigned int val;
> > +     int ret;
> > +
> > +     /*
> > +      * VCN33_WIFI and VCN33_BT are two separate enable bits for the same
> > +      * regulator. They share the same voltage setting and output pin.
> > +      * Instead of having two potentially conflicting regulators, just have
> > +      * one VCN33 regulator. Sync the two enable bits and only use one in
> > +      * the regulator device.
> > +      */
> > +     ret = regmap_read(mt6397->regmap, MT6358_LDO_VCN33_CON0_1, &val);
> > +     if (ret) {
> > +             dev_err(dev, "Failed to read VCN33_WIFI setting\n");
> > +             return ret;
> > +     }
> > +
> > +     if (!(val & BIT(0)))
> > +             return 0;
> > +
> > +     /* Sync VCN33_WIFI enable status to VCN33_BT */
> > +     ret = regmap_update_bits(mt6397->regmap, MT6358_LDO_VCN33_CON0_0, BIT(0), BIT(0));
> > +     if (ret) {
> > +             dev_err(dev, "Failed to sync VCN33_WIFI setting to VCN33_BT\n");
> > +             return ret;
> > +     }
> > +
> > +     /* Disable VCN33_WIFI */
> > +     ret = regmap_update_bits(mt6397->regmap, MT6358_LDO_VCN33_CON0_1, BIT(0), 0);
> > +     if (ret) {
> > +             dev_err(dev, "Failed to disable VCN33_BT\n");
> > +             return ret;
> > +     }
> > +
> > +     return 0;
> > +}
> > +
> >   static int mt6358_regulator_probe(struct platform_device *pdev)
> >   {
> >       struct mt6397_chip *mt6397 = dev_get_drvdata(pdev->dev.parent);
> >       struct regulator_config config = {};
> >       struct regulator_dev *rdev;
> >       struct mt6358_regulator_info *mt6358_info;
> > -     int i, max_regulator;
> > +     int i, max_regulator, ret;
> > +
> > +     ret = mt6358_sync_vcn33_setting(&pdev->dev);
> > +     if (ret)
> > +             return ret;
>
> I'd put this after the chip_id check, and I would also add a safety check for
> that...
>
>         switch (mt6397->chip_id) {
>         case MT6366_CHIP_ID:
>                 max_regulator = MT6366_MAX_REGULATOR;
>                 mt6358_info = mt6366_regulators;
>                 break;
>         case MT6358_CHIP_ID:
>                 max_regulator = MT6358_MAX_REGULATOR;
>                 mt6358_info = mt6358_regulators;
>                 break;
>         default:
>                 return -EINVAL;
>         }
>
>         ret = mt6358_sync_vcn33_setting(....)

Sounds good. We wouldn't want to be poking random bits in some other PMIC.

> ...but I agree with your point here about this being a strange design and
> also with your way of fixing the driver.

What I heard was that they support separate Bluetooth and WiFi drivers that
don't have a common reference counting framework for their regulator
supplies using this scheme. Maybe they are doing the power sequencing in
some small firmware.

ChenYu