Re: [PATCH 8/9] i2c: qcom-cci: add support of optional vbus-supply regulators

[Bjorn Andersson <bjorn.andersson@linaro.org>]

On Fri 04 Feb 03:41 PST 2022, Loic Poulain wrote:

> On Fri, 4 Feb 2022 at 12:03, Robert Foss <robert.foss@linaro.org> wrote:
> >
> > On Thu, 3 Feb 2022 at 17:47, Vladimir Zapolskiy
> > <vladimir.zapolskiy@linaro.org> wrote:
> > >
> > > The change adds handling of optional vbus regulators in the driver.
> > >
> > > Signed-off-by: Vladimir Zapolskiy <vladimir.zapolskiy@linaro.org>
> > > ---
> > >  drivers/i2c/busses/i2c-qcom-cci.c | 49 +++++++++++++++++++++++++++++++
> > >  1 file changed, 49 insertions(+)
> > >
> > > diff --git a/drivers/i2c/busses/i2c-qcom-cci.c b/drivers/i2c/busses/i2c-qcom-cci.c
> > > index 775945f7b4cd..2fc7f1f2616f 100644
> > > --- a/drivers/i2c/busses/i2c-qcom-cci.c
> > > +++ b/drivers/i2c/busses/i2c-qcom-cci.c
> > > @@ -11,6 +11,7 @@
> > >  #include <linux/of.h>
> > >  #include <linux/platform_device.h>
> > >  #include <linux/pm_runtime.h>
> > > +#include <linux/regulator/consumer.h>
> > >
> > >  #define CCI_HW_VERSION                         0x0
> > >  #define CCI_RESET_CMD                          0x004
> > > @@ -480,6 +481,20 @@ static void cci_disable_clocks(struct cci *cci)
> > >  static int __maybe_unused cci_suspend_runtime(struct device *dev)
> > >  {
> > >         struct cci *cci = dev_get_drvdata(dev);
> > > +       struct regulator *bus_regulator;
> > > +       unsigned int i;
> > > +
> > > +       for (i = 0; i < cci->data->num_masters; i++) {
> > > +               if (!cci->master[i].cci)
> > > +                       continue;
> > > +
> > > +               bus_regulator = cci->master[i].adap.bus_regulator;
> > > +               if (!bus_regulator)
> > > +                       continue;
> > > +
> > > +               if (regulator_is_enabled(bus_regulator) > 0)
> >
> > Is this check needed? No matter the current status of the regulator,
> > we'd like to disable it, and from my reading regulator_disable can be
> > called for already disabled regulators.
> 
> +1, but why do we even assign this regulator to each adapter, a
> simpler solution would be to have the regulator part of the cci
> struct, and simply disable/enable it on runtime suspend/resume,
> without extra loop/check.

But that implies that you always will have the same io-supply for your
two busses. Something that seems likely but I don't see that it's a
requirement.

Although as proposed "vbus" is acquired from the cci node and not the
individual bus anyways...

> I2C core does nothing with
> adap.bus_regulator anyway (5a7b95fb993e has been partially reverted).
> 

Thanks for the pointer, that looks like a much better and generic
solution. In particular if we specify the regulator per bus.

Regards,
Bjorn

> >
> > > +                       regulator_disable(bus_regulator);
> > > +       }
> > >
> > >         cci_disable_clocks(cci);
> > >         return 0;
> > > @@ -488,12 +503,30 @@ static int __maybe_unused cci_suspend_runtime(struct device *dev)
> > >  static int __maybe_unused cci_resume_runtime(struct device *dev)
> > >  {
> > >         struct cci *cci = dev_get_drvdata(dev);
> > > +       struct regulator *bus_regulator;
> > > +       unsigned int i;
> > >         int ret;
> > >
> > >         ret = cci_enable_clocks(cci);
> > >         if (ret)
> > >                 return ret;
> > >
> > > +       for (i = 0; i < cci->data->num_masters; i++) {
> > > +               if (!cci->master[i].cci)
> > > +                       continue;
> > > +
> > > +               bus_regulator = cci->master[i].adap.bus_regulator;
> > > +               if (!bus_regulator)
> > > +                       continue;
> > > +
> > > +               if (!regulator_is_enabled(bus_regulator)) {
> > > +                       ret = regulator_enable(bus_regulator);
> > > +                       if (ret)
> > > +                               dev_err(dev, "failed to enable regulator: %d\n",
> > > +                                       ret);
> > > +               }
> > > +       }
> > > +
> > >         cci_init(cci);
> > >         return 0;
> > >  }
> > > @@ -593,6 +626,7 @@ static int cci_probe(struct platform_device *pdev)
> > >         dev_dbg(dev, "CCI HW version = 0x%08x", val);
> > >
> > >         for_each_available_child_of_node(dev->of_node, child) {
> > > +               struct regulator *bus_regulator;
> > >                 struct cci_master *master;
> > >                 u32 idx;
> > >
> > > @@ -637,6 +671,21 @@ static int cci_probe(struct platform_device *pdev)
> > >                         master->cci = NULL;
> > >                         goto error_i2c;
> > >                 }
> > > +
> > > +               /*
> > > +                * It might be possible to find an optional vbus supply, but
> > > +                * it requires to pass the registration of an I2C adapter
> > > +                * device and its association with a bus device tree node.
> > > +                */
> > > +               bus_regulator = devm_regulator_get_optional(&master->adap.dev,
> > > +                                                           "vbus");
> > > +               if (IS_ERR(bus_regulator)) {
> > > +                       ret = PTR_ERR(bus_regulator);
> > > +                       if (ret == -EPROBE_DEFER)
> > > +                               goto error_i2c;
> > > +                       bus_regulator = NULL;
> > > +               }
> > > +               master->adap.bus_regulator = bus_regulator;
> > >         }
> > >
> > >         ret = cci_reset(cci);
> > > --
> > > 2.33.0
> > >
> >
> > With the above nit sorted, feel free to add my r-b.
> >
> > Reviewed-by: Robert Foss <robert.foss@linaro.org>