Re: [PATCH] phy: qcom-snps: Fixed order of enabling regulators

[Krishna Kurapati PSSNV]

On 2/21/2024 4:26 PM, Dmitry Baryshkov wrote:
> On Wed, 21 Feb 2024 at 12:32, Krishna Kurapati > <quic_kriskura@xxxxxxxxxxx> wrote:
[...]
> > ---
> >
> > Downstream kernels on QC targets use this sequence to power up
> > the phy and this has been tested extensively on multiple targets.
> > This change has been tested with upstream kernel on QCM6490-IDP
> > without EUD to ensure there is no loss or breakage of functionality.
> >
> >   drivers/phy/qualcomm/phy-qcom-snps-femto-v2.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/phy/qualcomm/phy-qcom-snps-femto-v2.c b/drivers/phy/qualcomm/phy-qcom-snps-femto-v2.c
> > index eb0b0f61d98e..e86d221b7397 100644
> > --- a/drivers/phy/qualcomm/phy-qcom-snps-femto-v2.c
> > +++ b/drivers/phy/qualcomm/phy-qcom-snps-femto-v2.c
> > @@ -79,7 +79,7 @@
> >   #define LS_FS_OUTPUT_IMPEDANCE_MASK            GENMASK(3, 0)
> >
> >   static const char * const qcom_snps_hsphy_vreg_names[] = {
> > -       "vdda-pll", "vdda33", "vdda18",
> > +       "vdda-pll", "vdda18", "vdda33",
>
> NAK.
> The driver uses regulator_bulk_enable, which enables all three
> regulators simultaneously via async calls, thus your change doesn't
> have any effect.
Hi Dmitry,

 Thanks for this information. I thought it was synchronous but you are 
right, I see in code they are async:

                async_schedule_domain(regulator_bulk_enable_async,
                                      &consumers[i], &async_domain);

 I think separating them out and calling regulator_enable on each one 
might work out.

> Also note, that these regulators are frequently shared between
> different consumers. As such, even if you have tight control of
> regulator ordering in the driver, other drivers might enable
> corresponding regulators on their own, breaking the ordering.

You are right. Let me check how the phy regulators are allocated in 
different femto phy targets.

Thanks for the review.

Regards,
Krishna,