Re: [PATCH 3/9] watchdog: s3c2410_wdt: update to use new exynos_pmu_*() apis

From: Peter Griffin <peter.griffin@linaro.org>
To: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc: arnd@arndb.de, robh+dt@kernel.org,
	krzysztof.kozlowski+dt@linaro.org,  linux@roeck-us.net,
	wim@linux-watchdog.org, conor+dt@kernel.org,
	 alim.akhtar@samsung.com, jaewon02.kim@samsung.com,
	chanho61.park@samsung.com,  semen.protsenko@linaro.org,
	kernel-team@android.com, tudor.ambarus@linaro.org,
	 andre.draszik@linaro.org, saravanak@google.com,
	willmcvicker@google.com,  linux-fsd@tesla.com,
	linux-watchdog@vger.kernel.org,  devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	 linux-arm-kernel@lists.infradead.org,
	linux-samsung-soc@vger.kernel.org
Subject: Re: [PATCH 3/9] watchdog: s3c2410_wdt: update to use new exynos_pmu_*() apis
Date: Tue, 23 Jan 2024 17:30:55 +0000	[thread overview]
Message-ID: <CADrjBPor5tMY4r0jOy7GH36auCU7dWn6Qn4ct89bsSMW4vAQOA@mail.gmail.com> (raw)
In-Reply-To: <da30a68a-e29f-45c8-aa73-02955255a457@linaro.org>

Hi Krzysztof,

Thanks for your review feedback.

On Tue, 23 Jan 2024 at 11:19, Krzysztof Kozlowski
<krzysztof.kozlowski@linaro.org> wrote:
>
> On 22/01/2024 23:57, Peter Griffin wrote:
> > Instead of obtaining the PMU regmap directly use the new exynos_pmu_*()
> > APIs. The exynos_pmu_ APIs allow support of newer Exynos SoCs that have
> > atomic set/clear bit hardware and platforms where the PMU registers can
> > only be accessed via SMC call.
> >
> > As all platforms that have PMU registers use these new APIs, remove the
> > syscon regmap lookup code, as it is now redundant.
> >
> > Signed-off-by: Peter Griffin <peter.griffin@linaro.org>
> > ---
> >  drivers/watchdog/Kconfig       |  1 +
> >  drivers/watchdog/s3c2410_wdt.c | 25 +++++++++----------------
> >  2 files changed, 10 insertions(+), 16 deletions(-)
> >
> > diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> > index 7d22051b15a2..b3e90e1ddf14 100644
> > --- a/drivers/watchdog/Kconfig
> > +++ b/drivers/watchdog/Kconfig
> > @@ -513,6 +513,7 @@ config S3C2410_WATCHDOG
> >       depends on ARCH_S3C64XX || ARCH_S5PV210 || ARCH_EXYNOS || COMPILE_TEST
> >       select WATCHDOG_CORE
> >       select MFD_SYSCON if ARCH_EXYNOS
> > +     select EXYNOS_PMU
>
> This does not look compatible with S3C64xx and S5Pv210.

Please refer to my reply to Guenter on how I propose fixing that in v2.

>
> >       help
> >         Watchdog timer block in the Samsung S3C64xx, S5Pv210 and Exynos
> >         SoCs. This will reboot the system when the timer expires with
> > diff --git a/drivers/watchdog/s3c2410_wdt.c b/drivers/watchdog/s3c2410_wdt.c
> > index 349d30462c8c..fd3a9ce870a0 100644
> > --- a/drivers/watchdog/s3c2410_wdt.c
> > +++ b/drivers/watchdog/s3c2410_wdt.c
> > @@ -28,6 +28,8 @@
> >  #include <linux/regmap.h>
> >  #include <linux/delay.h>
> >
> > +#include <linux/soc/samsung/exynos-pmu.h>
> > +
> >  #define S3C2410_WTCON                0x00
> >  #define S3C2410_WTDAT                0x04
> >  #define S3C2410_WTCNT                0x08
> > @@ -187,7 +189,6 @@ struct s3c2410_wdt {
> >       struct watchdog_device  wdt_device;
> >       struct notifier_block   freq_transition;
> >       const struct s3c2410_wdt_variant *drv_data;
> > -     struct regmap *pmureg;
> >  };
> >
> >  static const struct s3c2410_wdt_variant drv_data_s3c2410 = {
> > @@ -355,8 +356,8 @@ static int s3c2410wdt_disable_wdt_reset(struct s3c2410_wdt *wdt, bool mask)
> >       const u32 val = mask ? mask_val : 0;
> >       int ret;
> >
> > -     ret = regmap_update_bits(wdt->pmureg, wdt->drv_data->disable_reg,
> > -                              mask_val, val);
> > +     ret = exynos_pmu_update(wdt->drv_data->disable_reg,
> > +                             mask_val, val);
> >       if (ret < 0)
> >               dev_err(wdt->dev, "failed to update reg(%d)\n", ret);
> >
> > @@ -370,8 +371,8 @@ static int s3c2410wdt_mask_wdt_reset(struct s3c2410_wdt *wdt, bool mask)
> >       const u32 val = (mask ^ val_inv) ? mask_val : 0;
> >       int ret;
> >
> > -     ret = regmap_update_bits(wdt->pmureg, wdt->drv_data->mask_reset_reg,
> > -                              mask_val, val);
> > +     ret = exynos_pmu_update(wdt->drv_data->mask_reset_reg,
> > +                             mask_val, val);
> >       if (ret < 0)
> >               dev_err(wdt->dev, "failed to update reg(%d)\n", ret);
> >
> > @@ -384,8 +385,8 @@ static int s3c2410wdt_enable_counter(struct s3c2410_wdt *wdt, bool en)
> >       const u32 val = en ? mask_val : 0;
> >       int ret;
> >
> > -     ret = regmap_update_bits(wdt->pmureg, wdt->drv_data->cnt_en_reg,
> > -                              mask_val, val);
> > +     ret = exynos_pmu_update(wdt->drv_data->cnt_en_reg,
> > +                             mask_val, val);
> >       if (ret < 0)
> >               dev_err(wdt->dev, "failed to update reg(%d)\n", ret);
> >
> > @@ -617,7 +618,7 @@ static inline unsigned int s3c2410wdt_get_bootstatus(struct s3c2410_wdt *wdt)
> >       if (!(wdt->drv_data->quirks & QUIRK_HAS_PMU_RST_STAT))
> >               return 0;
> >
> > -     ret = regmap_read(wdt->pmureg, wdt->drv_data->rst_stat_reg, &rst_stat);
> > +     ret = exynos_pmu_read(wdt->drv_data->rst_stat_reg, &rst_stat);
> >       if (ret)
> >               dev_warn(wdt->dev, "Couldn't get RST_STAT register\n");
> >       else if (rst_stat & BIT(wdt->drv_data->rst_stat_bit))
> > @@ -698,14 +699,6 @@ static int s3c2410wdt_probe(struct platform_device *pdev)
> >       if (ret)
> >               return ret;
> >
> > -     if (wdt->drv_data->quirks & QUIRKS_HAVE_PMUREG) {
> > -             wdt->pmureg = syscon_regmap_lookup_by_phandle(dev->of_node,
> > -                                             "samsung,syscon-phandle");
> > -             if (IS_ERR(wdt->pmureg))
> > -                     return dev_err_probe(dev, PTR_ERR(wdt->pmureg),
> > -                                          "syscon regmap lookup failed.\n");
>
>
> Continuing topic from the binding: I don't see how you handle probe
> deferral, suspend ordering.

The current implementation is simply relying on exynos-pmu being
postcore_initcall level.

I was just looking around for any existing Linux APIs that could be a
more robust solution. It looks like

of_parse_phandle()
and
of_find_device_by_node();

Are often used to solve this type of probe deferral issue between
devices. Is that what you would recommend using? Or is there something
even better?

Thanks,

Peter