Re: [PATCH 6/6] regulator: qcom_smd: Add support to define the bootup voltage

[Devi Priya <quic_devipriy@xxxxxxxxxxx>]

On 1/31/2023 3:07 PM, Dmitry Baryshkov wrote:
> On 13/01/2023 17:03, devi priya wrote:
> > Kernel does not know the initial voltage set by the bootloaders.
> > During regulator registration, the voltage variable is just declared
> > and it is zero. Based on that, the regulator framework considers current
> > the voltage as zero and tries to bring up each regulator to minimum
> > the supported voltage.
> >
> > This introduces a dip in the voltage during kernel boot and gets
> > stabilized once the voltage scaling comes into picture.
> >
> > To avoid the voltage dip, adding support to define the
> > bootup voltage set by the boodloaders and based on it, regulator
> > framework understands that proper voltage is already set
> >
> > Co-developed-by: Praveenkumar I <quic_ipkumar@xxxxxxxxxxx>
> > Signed-off-by: Praveenkumar I <quic_ipkumar@xxxxxxxxxxx>
> > Signed-off-by: devi priya <quic_devipriy@xxxxxxxxxxx>
> > ---
> >   drivers/regulator/qcom_smd-regulator.c | 6 +++++-
> >   1 file changed, 5 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/regulator/qcom_smd-regulator.c 
> > b/drivers/regulator/qcom_smd-regulator.c
> > index 1eb17d378897..49a36b07397c 100644
> > --- a/drivers/regulator/qcom_smd-regulator.c
> > +++ b/drivers/regulator/qcom_smd-regulator.c
> > @@ -800,6 +800,7 @@ struct rpm_regulator_data {
> >       u32 id;
> >       const struct regulator_desc *desc;
> >       const char *supply;
> > +    int boot_uV; /* To store the bootup voltage set by bootloaders */
> >   };
> >   static const struct rpm_regulator_data rpm_mp5496_regulators[] = {
> > @@ -809,7 +810,7 @@ static const struct rpm_regulator_data 
> > rpm_mp5496_regulators[] = {
> >   };
> >   static const struct rpm_regulator_data 
> > rpm_ipq9574_mp5496_regulators[] = {
> > -    { "s1", QCOM_SMD_RPM_SMPA, 1, &ipq9574_mp5496_smpa1, "s1" },
> > +    { "s1", QCOM_SMD_RPM_SMPA, 1, &ipq9574_mp5496_smpa1, "s1", 875000 },
>
> I think this is a peculiarity of the particular board that than a 
> property of the PMIC. Please describe this in the board or SoC DTS if 
> the value can not be read using the software .
The bootup voltage is actually blown into the OTP register of the PMIC 
and so, it remains the same across boards for IPQ9574 SoC
> >       {}
> >   };
> > @@ -1394,6 +1395,9 @@ static int rpm_regulator_init_vreg(struct 
> > qcom_rpm_reg *vreg, struct device *dev
> >       vreg->type    = rpm_data->type;
> >       vreg->id    = rpm_data->id;
> > +    if (rpm_data->boot_uV)
> > +        vreg->uV = rpm_data->boot_uV;
> > +
> >       memcpy(&vreg->desc, rpm_data->desc, sizeof(vreg->desc));
> >       vreg->desc.name = rpm_data->name;
> >       vreg->desc.supply_name = rpm_data->supply;
Best Regards,
Devi Priya