Re: [PATCH v4 5/7] watchdog: rzv2h: Add syscon support for WDTDCR

[Lad, Prabhakar]

Hi Guenter,

On Thu, Sep 17, 2026 at 2:12 AM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
>
> Hi,
>
> On Mon, Aug 17, 2026 at 08:25:38PM +0100, Prabhakar wrote:
> > From: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> >
> > On RZ/T2H and RZ/N2H SoCs, the WDTDCR (WDT Debug Control Register) resides
> > in the second register region of the CPG/MSSR block. Since this
> > multi-function block is shared with other peripherals, it is exposed via a
> > syscon regmap interface.
> >
> > Look up the SYSC regmap using the optional "renesas,sysc" property and
> > derive the WDTDCR offset from the watchdog instance index.
> >
> > Retain the existing MMIO-based access method when the "renesas,sysc"
> > property is absent to preserve compatibility with existing DT's.
> >
> > Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx>
> > Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
>
> Can I apply this patch without the other patches of the series ?
>
I posted the v5 series here addressing Sashiko's comments.

https://lore.kernel.org/all/20260911111731.3404308-1-prabhakar.mahadev-lad.rj@xxxxxxxxxxxxxx/

Cheers,
Prabhakar

> Thanks,
> Guenter
>
> > ---
> > v3->v4:
> > - No change
> >
> > v2->v3:
> > - Made use of the new "renesas,sysc" phandle-array property to access the
> >   WDTDCR register via the CPG/MSSR syscon node.
> > - Updated commit message
> >
> > v1->v2:
> > - No change.
> > ---
> >  drivers/watchdog/Kconfig     |  1 +
> >  drivers/watchdog/rzv2h_wdt.c | 56 +++++++++++++++++++++++++++++-------
> >  2 files changed, 46 insertions(+), 11 deletions(-)
> >
> > diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> > index f7d0a0c2c0ef..3c4fc9916d8c 100644
> > --- a/drivers/watchdog/Kconfig
> > +++ b/drivers/watchdog/Kconfig
> > @@ -1046,6 +1046,7 @@ config RENESAS_RZV2HWDT
> >       depends on ARCH_RENESAS || COMPILE_TEST
> >       depends on PM || COMPILE_TEST
> >       select WATCHDOG_CORE
> > +     select MFD_SYSCON
> >       help
> >         This driver adds watchdog support for the integrated watchdogs in the
> >         Renesas RZ/{G3E,V2H(P)} SoCs. These watchdogs can be used to reset a
> > diff --git a/drivers/watchdog/rzv2h_wdt.c b/drivers/watchdog/rzv2h_wdt.c
> > index 8af2f33b5680..04ea962da837 100644
> > --- a/drivers/watchdog/rzv2h_wdt.c
> > +++ b/drivers/watchdog/rzv2h_wdt.c
> > @@ -8,6 +8,7 @@
> >  #include <linux/delay.h>
> >  #include <linux/io.h>
> >  #include <linux/kernel.h>
> > +#include <linux/mfd/syscon.h>
> >  #include <linux/module.h>
> >  #include <linux/of.h>
> >  #include <linux/platform_device.h>
> > @@ -44,6 +45,11 @@
> >
> >  #define WDT_DEFAULT_TIMEOUT  60U
> >
> > +#define RZT2H_WDT_MAX_INSTANCES      6
> > +
> > +#define RZT2H_SYS_BLOCK1(n)  (BIT(16) | (0x5100 + (n) * 4))
> > +#define RZT2H_WDTDCR_OFFSET(n)       RZT2H_SYS_BLOCK1(n)
> > +
> >  static bool nowayout = WATCHDOG_NOWAYOUT;
> >  module_param(nowayout, bool, 0);
> >  MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
> > @@ -64,14 +70,19 @@ struct rzv2h_of_data {
> >       bool wdtdcr;
> >  };
> >
> > +struct rzv2h_sysc_wdtdcr {
> > +     struct regmap *regmap;
> > +     unsigned int offset;
> > +};
> > +
> >  struct rzv2h_wdt_priv {
> >       void __iomem *base;
> > -     struct regmap *wdtdcr_regmap;
> >       struct clk *pclk;
> >       struct clk *oscclk;
> >       struct reset_control *rstc;
> >       struct watchdog_device wdev;
> >       const struct rzv2h_of_data *of_data;
> > +     struct rzv2h_sysc_wdtdcr sysc;
> >  };
> >
> >  static int rzv2h_wdt_ping(struct watchdog_device *wdev)
> > @@ -90,12 +101,16 @@ static int rzv2h_wdt_ping(struct watchdog_device *wdev)
> >
> >  static int rzt2h_wdt_wdtdcr_count_stop(struct rzv2h_wdt_priv *priv)
> >  {
> > -     return regmap_set_bits(priv->wdtdcr_regmap, WDTDCR, WDTDCR_WDTSTOPCTRL);
> > +     struct rzv2h_sysc_wdtdcr *sysc = &priv->sysc;
> > +
> > +     return regmap_set_bits(sysc->regmap, sysc->offset, WDTDCR_WDTSTOPCTRL);
> >  }
> >
> >  static int rzt2h_wdt_wdtdcr_count_start(struct rzv2h_wdt_priv *priv)
> >  {
> > -     return regmap_clear_bits(priv->wdtdcr_regmap, WDTDCR, WDTDCR_WDTSTOPCTRL);
> > +     struct rzv2h_sysc_wdtdcr *sysc = &priv->sysc;
> > +
> > +     return regmap_clear_bits(sysc->regmap, sysc->offset, WDTDCR_WDTSTOPCTRL);
> >  }
> >
> >  static void rzv2h_wdt_setup(struct watchdog_device *wdev, u16 wdtcr)
> > @@ -284,17 +299,36 @@ static const struct regmap_config rzv2h_wdtdcr_regmap_config = {
> >  static int rzt2h_wdt_wdtdcr_init(struct platform_device *pdev,
> >                                struct rzv2h_wdt_priv *priv)
> >  {
> > -     void __iomem *wdtdcr;
> > +     struct device_node *np = pdev->dev.of_node;
> > +     bool syscon_present = of_property_present(np, "renesas,sysc");
> > +     struct rzv2h_sysc_wdtdcr *sysc = &priv->sysc;
> >       int ret;
> >
> > -     wdtdcr = devm_platform_ioremap_resource(pdev, 1);
> > -     if (IS_ERR(wdtdcr))
> > -             return PTR_ERR(wdtdcr);
> > +     if (syscon_present) {
> > +             unsigned int wdt_index;
> >
> > -     priv->wdtdcr_regmap = devm_regmap_init_mmio(&pdev->dev, wdtdcr,
> > -                                                 &rzv2h_wdtdcr_regmap_config);
> > -     if (IS_ERR(priv->wdtdcr_regmap))
> > -             return PTR_ERR(priv->wdtdcr_regmap);
> > +             sysc->regmap = syscon_regmap_lookup_by_phandle_args(np, "renesas,sysc",
> > +                                                                 1, &wdt_index);
> > +             if (IS_ERR(sysc->regmap))
> > +                     return PTR_ERR(sysc->regmap);
> > +
> > +             if (wdt_index >= RZT2H_WDT_MAX_INSTANCES)
> > +                     return -EINVAL;
> > +
> > +             sysc->offset = RZT2H_WDTDCR_OFFSET(wdt_index);
> > +     } else {
> > +             void __iomem *wdtdcr;
> > +
> > +             wdtdcr = devm_platform_ioremap_resource(pdev, 1);
> > +             if (IS_ERR(wdtdcr))
> > +                     return PTR_ERR(wdtdcr);
> > +
> > +             sysc->regmap = devm_regmap_init_mmio(&pdev->dev, wdtdcr,
> > +                                                  &rzv2h_wdtdcr_regmap_config);
> > +             if (IS_ERR(sysc->regmap))
> > +                     return PTR_ERR(sysc->regmap);
> > +             sysc->offset = WDTDCR;
> > +     }
> >
> >       ret = pm_runtime_resume_and_get(&pdev->dev);
> >       if (ret)