Re: [RFC PATCH] watchdog: rzv2h_wdt: Add support to retrieve the bootstatus information

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

On 12/13/24 09:44, Prabhakar wrote:
> From: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> 
> On the RZ/V2H(P) SoC we can determine if the current boot is due to
> `Power-on-Reset` or due to the `Watchdog`. The information used to
> determine this is present on the CPG block.
> 
> The CPG_ERROR_RSTm(m = 2 -8 ) registers are set in response to an error
> interrupt causing an reset. CPG_ERROR_RST2[ERROR_RST1] is set if there
> was an underflow/overflow on WDT1 causing an error interrupt.
> 
> To fetch this information from CPG block `syscon` is used and bootstatus
> field in the watchdog device is updated based on the
> CPG_ERROR_RST2[ERROR_RST1] bit. Upon consumig CPG_ERROR_RST2[ERROR_RST1]
> bit we are also clearing it.
> 
> Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
> ---
> @Geert, I intend to drop WDT0/2/3 nodes (and related clocks) as HW manual
> says WDT1 is for CA55 (I'll first confirm this internally)
> 
> Hi Geert/Rob,
> 
> I havent included a binding changes as part of the RFC as I wanted to get
> some initial feedback on the implementation. Currently CPG block doesnt
> have the "syscon" this patch has been tested with below diff to SoC DTSI
> 
> Cheers,
> Prabhakar
> 
> Changes to SoC DTSI:
> @@ -243,7 +243,7 @@ pinctrl: pinctrl@10410000 {
>                  };
> 
>                  cpg: clock-controller@10420000 {
> -                       compatible = "renesas,r9a09g057-cpg";
> +                       compatible = "renesas,r9a09g057-cpg", "syscon";
>                          reg = <0 0x10420000 0 0x10000>;
>                          clocks = <&audio_extal_clk>, <&rtxin_clk>, <&qextal_clk>;
>                          clock-names = "audio_extal", "rtxin", "qextal";
> @@ -455,6 +456,7 @@ wdt1: watchdog@14400000 {
>                          clock-names = "pclk", "oscclk";
>                          resets = <&cpg 0x76>;
>                          power-domains = <&cpg>;
> +                       syscon = <&cpg>;
>                          status = "disabled";
>                  };
> 
> ---
>   drivers/watchdog/rzv2h_wdt.c | 27 ++++++++++++++++++++++++++-
>   1 file changed, 26 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/watchdog/rzv2h_wdt.c b/drivers/watchdog/rzv2h_wdt.c
> index 8defd0241213..8e0901bb7d2b 100644
> --- a/drivers/watchdog/rzv2h_wdt.c
> +++ b/drivers/watchdog/rzv2h_wdt.c
> @@ -4,14 +4,17 @@
>    *
>    * Copyright (C) 2024 Renesas Electronics Corporation.
>    */
> +#include <linux/bitfield.h>
>   #include <linux/clk.h>
>   #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>
>   #include <linux/pm_runtime.h>
> +#include <linux/regmap.h>
>   #include <linux/reset.h>
>   #include <linux/units.h>
>   #include <linux/watchdog.h>
> @@ -40,6 +43,10 @@
>   
>   #define WDT_DEFAULT_TIMEOUT	60U
>   
> +#define CPG_ERROR_RST2			0xb40
> +#define CPG_ERROR_RST2_ERR_RST1		BIT(1)
> +#define CPG_ERROR_RST2_ERR_RST1_WEN	(BIT(1) << 16)

I could understand BIT(17) or BIT(1 + 16) or

#define CPG_ERROR_RST2_ERR_RST1_BIT	1
#define CPG_ERROR_RST2_ERR_RST1		BIT(CPG_ERROR_RST2_ERR_RST1_BIT)
#define CPG_ERROR_RST2_ERR_RST1_WEN	BIT(CPG_ERROR_RST2_ERR_RST1_BIT + 16)

but "BIT(1) << 16" really does not add value.

> +
>   static bool nowayout = WATCHDOG_NOWAYOUT;
>   module_param(nowayout, bool, 0);
>   MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
> @@ -135,7 +142,7 @@ static int rzv2h_wdt_stop(struct watchdog_device *wdev)
>   }
>   
>   static const struct watchdog_info rzv2h_wdt_ident = {
> -	.options = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT,
> +	.options = WDIOF_MAGICCLOSE | WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT | WDIOF_CARDRESET,
>   	.identity = "Renesas RZ/V2H WDT Watchdog",
>   };
>   
> @@ -207,12 +214,29 @@ static int rzv2h_wdt_probe(struct platform_device *pdev)
>   {
>   	struct device *dev = &pdev->dev;
>   	struct rzv2h_wdt_priv *priv;
> +	struct regmap *regmap;
> +	unsigned int buf;

That is a bad variable name since it suggests a buffer, not some
register content.

>   	int ret;
>   
>   	priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL);
>   	if (!priv)
>   		return -ENOMEM;
>   
> +	regmap = syscon_regmap_lookup_by_phandle(dev->of_node, "syscon");
> +	if (IS_ERR(regmap))
> +		return PTR_ERR(regmap);
> +

That is a change in behavior. Up to now the syscon phandle did not have to exist
for the driver to work. Is it guaranteed to not result in regressions on systems
where it doesn't ? Also, is this documented ? I don't seem to be able to find it.

> +	ret = regmap_read(regmap, CPG_ERROR_RST2, &buf);
> +	if (ret)
> +		return -EINVAL;

Pass error codes back to caller. This is most definitely not an
"Invalid argument".

"
> +
> +	if (buf & CPG_ERROR_RST2_ERR_RST1) {
> +		ret = regmap_write(regmap, CPG_ERROR_RST2,
> +				   CPG_ERROR_RST2_ERR_RST1_WEN | CPG_ERROR_RST2_ERR_RST1);
> +		if (ret)
> +			return -EINVAL;

Same as above.

> +	}
> +
>   	priv->base = devm_platform_ioremap_resource(pdev, 0);
>   	if (IS_ERR(priv->base))
>   		return PTR_ERR(priv->base);
> @@ -243,6 +267,7 @@ static int rzv2h_wdt_probe(struct platform_device *pdev)
>   	priv->wdev.info = &rzv2h_wdt_ident;
>   	priv->wdev.ops = &rzv2h_wdt_ops;
>   	priv->wdev.parent = dev;
> +	priv->wdev.bootstatus = buf & CPG_ERROR_RST2_ERR_RST1 ? WDIOF_CARDRESET : 0;
>   	watchdog_set_drvdata(&priv->wdev, priv);
>   	watchdog_set_nowayout(&priv->wdev, nowayout);
>   	watchdog_stop_on_unregister(&priv->wdev);