Re: [PATCH] drivers: nvmem: Fix voltage settings for QTI qfprom-efuse

[Rajendra Nayak]

On 2/5/2021 8:25 PM, Doug Anderson wrote:
> Hi,
>
> On Fri, Feb 5, 2021 at 3:29 AM Ravi Kumar Bokka <rbokka@xxxxxxxxxxxxxx> wrote:
> > QFPROM controller hardware requires 1.8V min for fuse blowing.
> > So, this change sets the voltage to 1.8V, required to blow the fuse
> > for qfprom-efuse controller.
> >
> > To disable fuse blowing, we set the voltage to 0V since this may
> > be a shared rail and may be able to run at a lower rate when we're
> > not blowing fuses.
> >
> > Fixes: 93b4e49f8c86 ("nvmem: qfprom: Add fuse blowing support")
> > Reported-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
> > Suggested-by: Douglas Anderson <dianders@xxxxxxxxxxxx>
> > Signed-off-by: Ravi Kumar Bokka <rbokka@xxxxxxxxxxxxxx>
> > ---
> >   drivers/nvmem/qfprom.c | 21 +++++++++++++++++++++
> >   1 file changed, 21 insertions(+)
> >
> > diff --git a/drivers/nvmem/qfprom.c b/drivers/nvmem/qfprom.c
> > index 6cace24..100d69d 100644
> > --- a/drivers/nvmem/qfprom.c
> > +++ b/drivers/nvmem/qfprom.c
> > @@ -127,6 +127,16 @@ static void qfprom_disable_fuse_blowing(const struct qfprom_priv *priv,
> >   {
> >          int ret;
> >
> > +       /*
> > +        * This may be a shared rail and may be able to run at a lower rate
> > +        * when we're not blowing fuses.  At the moment, the regulator framework
> > +        * applies voltage constraints even on disabled rails, so remove our
> > +        * constraints and allow the rail to be adjusted by other users.
>
> Some year maybe I'll try to fix the regulator framework to not count
> voltage constraints for disbled rails, or perhaps have it be optional.
> ;-)  In theory it should be much easier after the patches we already
> landed not to count current requests for disabled rails...
>
>
> > +        */
> > +       ret = regulator_set_voltage(priv->vcc, 0, INT_MAX);
> > +       if (ret)
> > +               dev_warn(priv->dev, "Failed to set 0 voltage (ignoring)\n");
> > +
> >          ret = regulator_disable(priv->vcc);
> >          if (ret)
> >                  dev_warn(priv->dev, "Failed to disable regulator (ignoring)\n");
> > @@ -172,6 +182,17 @@ static int qfprom_enable_fuse_blowing(const struct qfprom_priv *priv,
> >                  goto err_clk_prepared;
> >          }
> >
> > +       /*
> > +        * Hardware requires 1.8V min for fuse blowing; this may be
> > +        * a rail shared do don't specify a max--regulator constraints
> > +        * will handle.
> > +        */
> > +       ret = regulator_set_voltage(priv->vcc, 1800000, INT_MAX);
> > +       if (ret) {
> > +               dev_err(priv->dev, "Failed to set 1.8 voltage\n");
> > +               goto err_clk_rate_set;
> > +       }
> > +
>
> Looks right to me.  Assuming that this works.
>
> Reviewed-by: Douglas Anderson <dianders@xxxxxxxxxxxx>

Srini, any plans to queue this up for merge?  

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