linux-kernel - Re: [PATCH v2 2/2] watchdog: s3c2410_wdt: use exynos_get_pmu_regmap_by

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Message-ID: <CAPLW+4mG2RkUgDbBBzrgCAW3covbr9eCQEFje1pYxj2hzVykug@mail.gmail.com>
Date: Mon, 29 Jan 2024 21:38:05 -0600
From: Sam Protsenko <semen.protsenko@...aro.org>
To: Saravana Kannan <saravanak@...gle.com>, Peter Griffin <peter.griffin@...aro.org>
Cc: arnd@...db.de, krzysztof.kozlowski@...aro.org, linux@...ck-us.net, 
	wim@...ux-watchdog.org, alim.akhtar@...sung.com, jaewon02.kim@...sung.com, 
	kernel-team@...roid.com, tudor.ambarus@...aro.org, andre.draszik@...aro.org, 
	willmcvicker@...gle.com, linux-fsd@...la.com, linux-watchdog@...r.kernel.org, 
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-samsung-soc@...r.kernel.org
Subject: Re: [PATCH v2 2/2] watchdog: s3c2410_wdt: use exynos_get_pmu_regmap_by_phandle()
 for PMU regs

On Mon, Jan 29, 2024 at 4:25 PM Saravana Kannan <saravanak@...gle.com> wrote:
>
> On Mon, Jan 29, 2024 at 1:19 PM Peter Griffin <peter.griffin@...aro.org> wrote:
> >
> > Obtain the PMU regmap using the new API added to exynos-pmu driver rather
> > than syscon_regmap_lookup_by_phandle(). As this driver no longer depends
> > on mfd syscon remove that header and Kconfig dependency.
> >
> > Signed-off-by: Peter Griffin <peter.griffin@...aro.org>
> > ---
> >  drivers/watchdog/Kconfig       | 1 -
> >  drivers/watchdog/s3c2410_wdt.c | 9 +++++----
> >  2 files changed, 5 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> > index 7d22051b15a2..d78fe7137799 100644
> > --- a/drivers/watchdog/Kconfig
> > +++ b/drivers/watchdog/Kconfig
> > @@ -512,7 +512,6 @@ config S3C2410_WATCHDOG
> >         tristate "S3C6410/S5Pv210/Exynos Watchdog"
> >         depends on ARCH_S3C64XX || ARCH_S5PV210 || ARCH_EXYNOS || COMPILE_TEST
> >         select WATCHDOG_CORE
> > -       select MFD_SYSCON if ARCH_EXYNOS

That reminds me: now that exynos-pmu driver uses regmap API, does it
make sense to add something like "select REGMAP" to EXYNOS_PMU option?

> >         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..a1e2682c7e57 100644
> > --- a/drivers/watchdog/s3c2410_wdt.c
> > +++ b/drivers/watchdog/s3c2410_wdt.c
> > @@ -24,9 +24,9 @@
> >  #include <linux/slab.h>
> >  #include <linux/err.h>
> >  #include <linux/of.h>
> > -#include <linux/mfd/syscon.h>
> >  #include <linux/regmap.h>
> >  #include <linux/delay.h>
> > +#include <linux/soc/samsung/exynos-pmu.h>
> >
> >  #define S3C2410_WTCON          0x00
> >  #define S3C2410_WTDAT          0x04
> > @@ -699,11 +699,12 @@ static int s3c2410wdt_probe(struct platform_device *pdev)
> >                 return ret;
> >
> >         if (wdt->drv_data->quirks & QUIRKS_HAVE_PMUREG) {
> > -               wdt->pmureg = syscon_regmap_lookup_by_phandle(dev->of_node,
> > -                                               "samsung,syscon-phandle");
> > +
> > +               wdt->pmureg = exynos_get_pmu_regmap_by_phandle(dev->of_node,
> > +                                                "samsung,syscon-phandle");
>

This looks so much better than approach taken in v1, as for my taste.
For this patch:

Reviewed-by: Sam Protsenko <semen.protsenko@...aro.org>

> IIUC, the exynos PMU driver is registering a regmap interface with
> regmap framework. So, can't we get the remap from the framework
> instead of directly talking to the PMU driver?
>

Peter is basically re-implementing syscon driver with overridden
operations, as a part of exynos-pmu driver, in previous patch. Which
means syscon API can't be used anymore to obtain the regmap. Do you
have particular API in mind that allows getting a random regmap
registered with devm_regmap_init()?

> -Saravana
>
> >                 if (IS_ERR(wdt->pmureg))
> >                         return dev_err_probe(dev, PTR_ERR(wdt->pmureg),
> > -                                            "syscon regmap lookup failed.\n");
> > +                                            "PMU regmap lookup failed.\n");
> >         }
> >
> >         wdt_irq = platform_get_irq(pdev, 0);
> > --
> > 2.43.0.429.g432eaa2c6b-goog
> >