Re: [PATCH v2 3/7] regulator: qcom-labibb: Implement pull-down, softstart, active discharge

[AngeloGioacchino Del Regno]

Il 15/01/21 05:53, Bjorn Andersson ha scritto:
> On Wed 13 Jan 13:42 CST 2021, AngeloGioacchino Del Regno wrote:
>
> > Soft start is required to avoid inrush current during LAB ramp-up and
> > IBB ramp-down, protecting connected hardware to which we supply voltage.
> >
> > Since soft start is configurable on both LAB and IBB regulators, it
> > was necessary to add two DT properties, respectively "qcom,soft-start-us"
> > to control LAB ramp-up and "qcom,discharge-resistor-kohms" to control
> > the discharge resistor for IBB ramp-down, which obviously brought the
> > need of implementing a of_parse callback for both regulators.
> >
> > Finally, also implement pull-down mode in order to avoid unpredictable
> > behavior when the regulators are disabled (random voltage spikes etc).
> >
> > Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxxx>
> > ---
> >   drivers/regulator/qcom-labibb-regulator.c | 94 +++++++++++++++++++++++
> >   1 file changed, 94 insertions(+)
> >
> > diff --git a/drivers/regulator/qcom-labibb-regulator.c b/drivers/regulator/qcom-labibb-regulator.c
> > index d364f54ad294..38ab1eba1c59 100644
> > --- a/drivers/regulator/qcom-labibb-regulator.c
> > +++ b/drivers/regulator/qcom-labibb-regulator.c
> > @@ -29,12 +29,23 @@
> >   #define LABIBB_STATUS1_VREG_OK_BIT	BIT(7)
> >   #define LABIBB_CONTROL_ENABLE		BIT(7)
> >   
> > +#define REG_LABIBB_PD_CTL		0x47
> > + #define LAB_PD_CTL_MASK		GENMASK(1, 0)
> > + #define IBB_PD_CTL_MASK		(BIT(0) | BIT(7))
> > + #define LAB_PD_CTL_STRONG_PULL		BIT(0)
> > + #define IBB_PD_CTL_HALF_STRENGTH	BIT(0)
> > + #define IBB_PD_CTL_EN			BIT(7)
> > +
> >   #define REG_LABIBB_CURRENT_LIMIT	0x4b
> >    #define LAB_CURRENT_LIMIT_MASK		GENMASK(2, 0)
> >    #define IBB_CURRENT_LIMIT_MASK		GENMASK(4, 0)
> >    #define LAB_CURRENT_LIMIT_OVERRIDE_EN	BIT(3)
> >    #define LABIBB_CURRENT_LIMIT_EN	BIT(7)
> >   
> > +#define REG_IBB_PWRUP_PWRDN_CTL_1	0x58
> > + #define IBB_CTL_1_DISCHARGE_EN		BIT(2)
> > +
> > +#define REG_LABIBB_SOFT_START_CTL	0x5f
> >   #define REG_LABIBB_SEC_ACCESS		0xd0
> >    #define LABIBB_SEC_UNLOCK_CODE		0xa5
> >   
> > @@ -60,6 +71,8 @@ struct labibb_regulator {
> >   	struct labibb_current_limits	uA_limits;
> >   	u16				base;
> >   	u8				type;
> > +	u8				dischg_sel;
> > +	u8				soft_start_sel;
> >   };
> >   
> >   struct labibb_regulator_data {
> > @@ -120,6 +133,70 @@ static int qcom_labibb_get_current_limit(struct regulator_dev *rdev)
> >   	return (cur_step * lim->uA_step) + lim->uA_min;
> >   }
> >   
> > +static int qcom_labibb_set_soft_start(struct regulator_dev *rdev)
> > +{
> > +	struct labibb_regulator *vreg = rdev_get_drvdata(rdev);
> > +	u32 val = 0;
> > +
> > +	if (vreg->type == QCOM_IBB_TYPE)
> > +		val = vreg->dischg_sel;
> > +	else
> > +		val = vreg->soft_start_sel;
> > +
> > +	return regmap_write(rdev->regmap, rdev->desc->soft_start_reg, val);
> > +}
> > +
> > +static int qcom_labibb_get_table_sel(const int *table, int sz, u32 value)
> > +{
> > +	int i;
> > +
> > +	for (i = 0; i < sz; i++)
> > +		if (table[i] == value)
> > +			return i;
> > +	return -EINVAL;
> > +}
> > +
> > +/* IBB discharge resistor values in KOhms */
> > +static const int dischg_resistor_values[] = { 300, 64, 32, 16 };
> > +
> > +/* Soft start time in microseconds */
> > +static const int soft_start_values[] = { 200, 400, 600, 800 };
> > +
> > +static int qcom_labibb_of_parse_cb(struct device_node *np,
> > +				   const struct regulator_desc *desc,
> > +				   struct regulator_config *config)
> > +{
> > +	struct labibb_regulator *vreg = config->driver_data;
> > +	u32 dischg_kohms, soft_start_time;
> > +	int ret;
> > +
> > +	ret = of_property_read_u32(np, "qcom,discharge-resistor-kohms",
> > +				       &dischg_kohms);
> > +	if (ret)
> > +		dischg_kohms = 300;
>
> Nit, if you just initialize dischg_kohms to 300 during definition you
> can rely on of_property_read_u32() not updating the value on failure...

I can change it if that's really necessary, I did it like this in an
attempt of spoon-feed the logic to the reader, but perhaps just
initializing it during definition would achieve the same, anyway.

Should I?

> That said, I think this patch looks good.
>
> Reviewed-by: Bjorn Andersson <bjorn.andersson@xxxxxxxxxx>

Thank you!

> Regards,
> Bjorn