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

[Guenter Roeck <linux@roeck-us.net>]

Hi,

On Mon, Aug 17, 2026 at 08:25:38PM +0100, Prabhakar wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> 
> 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@bp.renesas.com>
> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>

Can I apply this patch without the other patches of the series ?

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)