Re: [PATCH v2 3/3] power: domain: Add Apple pmgr driver

[Mark Kettenis <mark.kettenis@xs4all.nl>]

> From: Simon Glass <sjg@chromium.org>
> Date: Wed, 29 Dec 2021 06:36:24 -0700
> 
> Hi Mark,
> 
> On Tue, 28 Dec 2021 at 07:27, Mark Kettenis <mark.kettenis@xs4all.nl> wrote:
> >
> > > From: Simon Glass <sjg@chromium.org>
> > > Date: Tue, 28 Dec 2021 01:34:16 -0700
> > >
> > > Hi Mark,
> > >
> > > On Thu, 23 Dec 2021 at 14:35, Mark Kettenis <kettenis@openbsd.org> wrote:
> > > >
> > > > This driver supports power domains for the power management
> > > > controller found on Apple SoCs.
> > > >
> > > > Signed-off-by: Mark Kettenis <kettenis@openbsd.org>
> > > > ---
> > > >  arch/arm/Kconfig                  |   3 +
> > > >  drivers/power/domain/Kconfig      |   8 +++
> > > >  drivers/power/domain/Makefile     |   1 +
> > > >  drivers/power/domain/apple-pmgr.c | 113 ++++++++++++++++++++++++++++++
> > > >  4 files changed, 125 insertions(+)
> > > >  create mode 100644 drivers/power/domain/apple-pmgr.c
> > >
> > > Reviewed-by: Simon Glass <sjg@chromium.org>
> > >
> > > nits below
> > >
> > > >
> > > > diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
> > > > index 59e031de04..40d3f66acb 100644
> > > > --- a/arch/arm/Kconfig
> > > > +++ b/arch/arm/Kconfig
> > > > @@ -938,6 +938,9 @@ config ARCH_APPLE
> > > >         select OF_BOARD
> > > >         select PINCTRL
> > > >         select POSITION_INDEPENDENT
> > > > +       select POWER_DOMAIN
> > > > +       select REGMAP
> > > > +       select SYSCON
> > > >         select SYSRESET
> > > >         select SYSRESET_WATCHDOG
> > > >         select SYSRESET_WATCHDOG_AUTO
> > > > diff --git a/drivers/power/domain/Kconfig b/drivers/power/domain/Kconfig
> > > > index 99b3f9ae71..6ef7a3b3a7 100644
> > > > --- a/drivers/power/domain/Kconfig
> > > > +++ b/drivers/power/domain/Kconfig
> > > > @@ -9,6 +9,14 @@ config POWER_DOMAIN
> > > >           domains). This may be used to save power. This API provides the
> > > >           means to control such power management hardware.
> > > >
> > > > +config APPLE_PMGR_POWER_DOMAIN
> > > > +       bool "Enable the Apple PMGR power domain driver"
> > > > +       depends on POWER_DOMAIN
> > > > +       default y if ARCH_APPLE
> > > > +       help
> > > > +         Enable support for manipulating the Apple M1 power domains via
> > > > +         MMIO mapped registers.
> > >
> > > Needs more detail here, perhaps a pointer to docs, or something about
> > > what the driver supports.
> >
> > Struggling to come up with more.  The "via MMIO mapped registers" is
> > already a bit silly.  There are no docs.  And the one line already
> > indicates what the driver supports.  Do you want me to add a sentence
> > that says the same thing but in different words?
> 
> What is PMGR?

Power ManaGeR?  Who knows?  It is wat Apple seems to call this thing.

> What power domains does the driver support? All of them or just a subset?

Again, we don't know.  It supports the power domains we know about.

This is revers-engineered and most of the naming comes from hints
dropped by Apple in their version of the device tree and/or the macOS
driver names.  The more we say here, the more likely it is wrong.

> > > > +
> > > >  config BCM6328_POWER_DOMAIN
> > > >         bool "Enable the BCM6328 power domain driver"
> > > >         depends on POWER_DOMAIN && ARCH_BMIPS
> > > > diff --git a/drivers/power/domain/Makefile b/drivers/power/domain/Makefile
> > > > index 3d1e5f073c..530ae35671 100644
> > > > --- a/drivers/power/domain/Makefile
> > > > +++ b/drivers/power/domain/Makefile
> > > > @@ -4,6 +4,7 @@
> > > >  #
> > > >
> > > >  obj-$(CONFIG_$(SPL_)POWER_DOMAIN) += power-domain-uclass.o
> > > > +obj-$(CONFIG_APPLE_PMGR_POWER_DOMAIN) += apple-pmgr.o
> > > >  obj-$(CONFIG_BCM6328_POWER_DOMAIN) += bcm6328-power-domain.o
> > > >  obj-$(CONFIG_IMX8_POWER_DOMAIN) += imx8-power-domain-legacy.o imx8-power-domain.o
> > > >  obj-$(CONFIG_IMX8M_POWER_DOMAIN) += imx8m-power-domain.o
> > > > diff --git a/drivers/power/domain/apple-pmgr.c b/drivers/power/domain/apple-pmgr.c
> > > > new file mode 100644
> > > > index 0000000000..08a30c8ebf
> > > > --- /dev/null
> > > > +++ b/drivers/power/domain/apple-pmgr.c
> > > > @@ -0,0 +1,113 @@
> > > > +// SPDX-License-Identifier: GPL-2.0+
> > > > +/*
> > > > + * Copyright (C) 2021 Mark Kettenis <kettenis@openbsd.org>
> > > > + */
> > > > +
> > > > +#include <common.h>
> > > > +#include <asm/io.h>
> > > > +#include <dm.h>
> > > > +#include <linux/err.h>
> > > > +#include <linux/bitfield.h>
> > > > +#include <power-domain-uclass.h>
> > > > +#include <regmap.h>
> > > > +#include <syscon.h>
> > > > +
> > > > +#define APPLE_PMGR_PS_TARGET   GENMASK(3, 0)
> > > > +#define APPLE_PMGR_PS_ACTUAL   GENMASK(7, 4)
> > > > +
> > > > +#define APPLE_PMGR_PS_ACTIVE   0xf
> > > > +#define APPLE_PMGR_PS_PWRGATE  0x0
> > > > +
> > > > +#define APPLE_PMGR_PS_SET_TIMEOUT      100
> > >
> > > TIMEOUT_MS ?
> > > _US ?
> >
> > _US
> >
> > > > +
> > > > +struct apple_pmgr_priv {
> > > > +       struct regmap *regmap;
> > > > +       u32 offset;
> > >
> > > Needs comment for struct
> >
> > Really?  I mean, I can add a "Device private data" comment, but that's
> > pretty much implied by the _priv and the vast majority of the drivers
> > don't do such a thing.
> 
> What is offset?

The offset into the register map for this particular power domain.
Adding a comment feels like stating the obvious to me.  But if you
feel it needs one, I can add it.

> > > > +};
> > > > +
> > > > +static int apple_pmgr_request(struct power_domain *power_domain)
> > > > +{
> > > > +       return 0;
> > > > +}
> > > > +
> > > > +static int apple_pmgr_rfree(struct power_domain *power_domain)
> > > > +{
> > > > +       return 0;
> > > > +}
> > > > +
> > > > +static int apple_pmgr_ps_set(struct power_domain *power_domain, u32 pstate)
> > > > +{
> > > > +       struct apple_pmgr_priv *priv = dev_get_priv(power_domain->dev);
> > > > +       uint reg;
> > > > +
> > > > +       regmap_update_bits(priv->regmap, priv->offset, APPLE_PMGR_PS_TARGET,
> > > > +                          FIELD_PREP(APPLE_PMGR_PS_TARGET, pstate));
> > > > +
> > > > +       return regmap_read_poll_timeout(
> > > > +               priv->regmap, priv->offset, reg,
> > > > +               (FIELD_GET(APPLE_PMGR_PS_ACTUAL, reg) == pstate), 1,
> > > > +               APPLE_PMGR_PS_SET_TIMEOUT);
> > > > +}
> > > > +
> > > > +static int apple_pmgr_on(struct power_domain *power_domain)
> > > > +{
> > > > +       return apple_pmgr_ps_set(power_domain, APPLE_PMGR_PS_ACTIVE);
> > > > +}
> > > > +
> > > > +static int apple_pmgr_off(struct power_domain *power_domain)
> > > > +{
> > > > +       return 0;
> > > > +}
> > > > +
> > > > +static int apple_pmgr_of_xlate(struct power_domain *power_domain,
> > > > +                              struct ofnode_phandle_args *args)
> > > > +{
> > > > +       if (args->args_count != 0) {
> > >
> > > s/ != 0//
> >
> > != 0 seems better here since that is the value we're checking for.
> 
> It can't be negative though.
> 
> [..]
> 
> Regards,
> Simon
>