Re: [PATCH 1/4] power: regulator: Trigger probe of regulators which are always-on or boot-on

Hi Caleb,

On Thu, 27 Jun 2024 at 09:48, Caleb Connolly <[email protected]> wrote:
>
>
>
> On 27/06/2024 10:37, Simon Glass wrote:
> > Hi Marek,
> >
> > On Thu, 27 Jun 2024 at 00:57, Marek Vasut <[email protected]> wrote:
> >>
> >> In case a regulator DT node contains regulator-always-on or regulator-boot-on
> >> property, make sure the regulator gets correctly configured by U-Boot on start
> >> up. Unconditionally probe such regulator drivers. This is a preparatory patch
> >> for introduction of .regulator_post_probe() which would trigger the regulator
> >> configuration.
> >>
> >> Parsing of regulator-always-on and regulator-boot-on DT property has been
> >> moved to regulator_post_bind() as the information is required early, the
> >> rest of the DT parsing has been kept in regulator_pre_probe() to avoid
> >> slowing down the boot process.
> >>
> >> Signed-off-by: Marek Vasut <[email protected]>
> >> ---
> >> Cc: Ben Wolsieffer <[email protected]>
> >> Cc: Caleb Connolly <[email protected]>
> >> Cc: Chris Morgan <[email protected]>
> >> Cc: Dragan Simic <[email protected]>
> >> Cc: Eugen Hristev <[email protected]>
> >> Cc: Francesco Dolcini <[email protected]>
> >> Cc: Heinrich Schuchardt <[email protected]>
> >> Cc: Jaehoon Chung <[email protected]>
> >> Cc: Jagan Teki <[email protected]>
> >> Cc: Jonas Karlman <[email protected]>
> >> Cc: Kever Yang <[email protected]>
> >> Cc: Kostya Porotchkin <[email protected]>
> >> Cc: Matteo Lisi <[email protected]>
> >> Cc: Mattijs Korpershoek <[email protected]>
> >> Cc: Max Krummenacher <[email protected]>
> >> Cc: Neil Armstrong <[email protected]>
> >> Cc: Patrice Chotard <[email protected]>
> >> Cc: Patrick Delaunay <[email protected]>
> >> Cc: Philipp Tomsich <[email protected]>
> >> Cc: Quentin Schulz <[email protected]>
> >> Cc: Sam Day <[email protected]>
> >> Cc: Simon Glass <[email protected]>
> >> Cc: Sumit Garg <[email protected]>
> >> Cc: Svyatoslav Ryhel <[email protected]>
> >> Cc: Thierry Reding <[email protected]>
> >> Cc: Tom Rini <[email protected]>
> >> Cc: Volodymyr Babchuk <[email protected]>
> >> Cc: [email protected]
> >> Cc: [email protected]
> >> Cc: [email protected]
> >> Cc: [email protected]
> >> Cc: [email protected]
> >> ---
> >>   drivers/power/regulator/regulator-uclass.c | 22 +++++++++++++++-------
> >>   1 file changed, 15 insertions(+), 7 deletions(-)
> >>
> >> diff --git a/drivers/power/regulator/regulator-uclass.c b/drivers/power/regulator/regulator-uclass.c
> >> index 66fd531da04..ccc4ef33d83 100644
> >> --- a/drivers/power/regulator/regulator-uclass.c
> >> +++ b/drivers/power/regulator/regulator-uclass.c
> >> @@ -433,6 +433,8 @@ static int regulator_post_bind(struct udevice *dev)
> >>          const char *property = "regulator-name";
> >>
> >>          uc_pdata = dev_get_uclass_plat(dev);
> >> +       uc_pdata->always_on = dev_read_bool(dev, "regulator-always-on");
> >> +       uc_pdata->boot_on = dev_read_bool(dev, "regulator-boot-on");
> >>
> >>          /* Regulator's mandatory constraint */
> >>          uc_pdata->name = dev_read_string(dev, property);
> >> @@ -444,13 +446,21 @@ static int regulator_post_bind(struct udevice *dev)
> >>                          return -EINVAL;
> >>          }
> >>
> >> -       if (regulator_name_is_unique(dev, uc_pdata->name))
> >> -               return 0;
> >> +       if (!regulator_name_is_unique(dev, uc_pdata->name)) {
> >> +               debug("'%s' of dev: '%s', has nonunique value: '%s\n",
> >> +                     property, dev->name, uc_pdata->name);
> >> +               return -EINVAL;
> >> +       }
> >>
> >> -       debug("'%s' of dev: '%s', has nonunique value: '%s\n",
> >> -             property, dev->name, uc_pdata->name);
> >> +       /*
> >> +        * In case the regulator has regulator-always-on or
> >> +        * regulator-boot-on DT property, trigger probe() to
> >> +        * configure its default state during startup.
> >> +        */
> >> +       if (uc_pdata->always_on && uc_pdata->boot_on)
> >> +               dev_or_flags(dev, DM_FLAG_PROBE_AFTER_BIND);
> >>
> >> -       return -EINVAL;
> >> +       return 0;
> >>   }
> >>
> >>   static int regulator_pre_probe(struct udevice *dev)
> >> @@ -473,8 +483,6 @@ static int regulator_pre_probe(struct udevice *dev)
> >>                                                  -ENODATA);
> >>          uc_pdata->max_uA = dev_read_u32_default(dev, "regulator-max-microamp",
> >>                                                  -ENODATA);
> >> -       uc_pdata->always_on = dev_read_bool(dev, "regulator-always-on");
> >> -       uc_pdata->boot_on = dev_read_bool(dev, "regulator-boot-on");
> >>          uc_pdata->ramp_delay = dev_read_u32_default(dev, "regulator-ramp-delay",
> >>                                                      0);
> >>          uc_pdata->force_off = dev_read_bool(dev, "regulator-force-boot-off");
> >> --
> >> 2.43.0
> >>
> >
> > This is reading a lot of DT stuff very early, which may be slow. It is
> > also reading from the DT in the bind() step which we sometimes have to
> > do, but try to avoid.
>
> Could we set up the livetree pre-bind? What about MMU? On armv8 at least
> this would have a huge impact on performance. I've done some
> measurements and there is at least 1 order of magnitude difference
> between parsing FDT with no caches vs parsing livetree with, it's huge.

That seems like a great idea to me, in general. The fact that SPL sets
up the MMU on armv8 makes it more practical.

But for this series I believe we are going to have to define what
happens in what phase. We have power_init_board() which is the old way
of doing this...but perhaps we could use that as a way to start up
regulators which are needed.

As to my question about whether this happens in SPL / pre-reloc /
proper, I forgot that we have the bootph tags for that, so it should
be fine. The main issue is that in U-Boot proper we will re-init the
regulators even though that has already been done. Probably that can
be handled by Kconfig or a flag in SPL handoff.


> >
> > Also this seems to happen in SPL and again pre-reloc and again in
> > U-Boot post-reloc?
> >
> > Should we have a step in the init sequence where we set up the
> > regulators, by calling regulators_enable_boot_on() ?

Regards,
Simon