linux-kernel - Re: [PATCH v6 2/2] watchdog: Add Renesas RZ/N1 Watchdog driver

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Date:   Wed, 27 Apr 2022 06:03:19 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Jean-Jacques Hiblot <jjhiblot@...phandler.com>,
        wim@...ux-watchdog.org, geert+renesas@...der.be,
        tzungbi@...nel.org, linux-watchdog@...r.kernel.org
Cc:     linux-renesas-soc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Phil Edworthy <phil.edworthy@...esas.com>
Subject: Re: [PATCH v6 2/2] watchdog: Add Renesas RZ/N1 Watchdog driver

On 4/13/22 01:25, Jean-Jacques Hiblot wrote:
> From: Phil Edworthy <phil.edworthy@...esas.com>
> 
> This is a driver for the standard WDT on the RZ/N1 devices. This WDT has
> very limited timeout capabilities. However, it can reset the device.
> To do so, the corresponding bits in the SysCtrl RSTEN register need to
> be enabled. This is not done by this driver.
> 
> Signed-off-by: Phil Edworthy <phil.edworthy@...esas.com>
> Signed-off-by: Jean-Jacques Hiblot <jjhiblot@...phandler.com>
> Reviewed-by: Tzung-Bi Shih <tzungbi@...nel.org>
> ---
>   drivers/watchdog/Kconfig    |   8 ++
>   drivers/watchdog/Makefile   |   1 +
>   drivers/watchdog/rzn1_wdt.c | 203 ++++++++++++++++++++++++++++++++++++
>   3 files changed, 212 insertions(+)
>   create mode 100644 drivers/watchdog/rzn1_wdt.c
> 
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index c4e82a8d863f..4d5e503c8950 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -883,6 +883,14 @@ config RENESAS_RZAWDT
>   	  This driver adds watchdog support for the integrated watchdogs in the
>   	  Renesas RZ/A SoCs. These watchdogs can be used to reset a system.
>   
> +config RENESAS_RZN1WDT
> +	tristate "Renesas RZ/N1 watchdog"
> +	depends on ARCH_RENESAS || COMPILE_TEST
> +	select WATCHDOG_CORE
> +	help
> +	  This driver adds watchdog support for the integrated watchdogs in the
> +	  Renesas RZ/N1 SoCs. These watchdogs can be used to reset a system.
> +
>   config RENESAS_RZG2LWDT
>   	tristate "Renesas RZ/G2L WDT Watchdog"
>   	depends on ARCH_RENESAS || COMPILE_TEST
> diff --git a/drivers/watchdog/Makefile b/drivers/watchdog/Makefile
> index f7da867e8782..38d38564f47b 100644
> --- a/drivers/watchdog/Makefile
> +++ b/drivers/watchdog/Makefile
> @@ -84,6 +84,7 @@ obj-$(CONFIG_LPC18XX_WATCHDOG) += lpc18xx_wdt.o
>   obj-$(CONFIG_BCM7038_WDT) += bcm7038_wdt.o
>   obj-$(CONFIG_RENESAS_WDT) += renesas_wdt.o
>   obj-$(CONFIG_RENESAS_RZAWDT) += rza_wdt.o
> +obj-$(CONFIG_RENESAS_RZN1WDT) += rzn1_wdt.o
>   obj-$(CONFIG_RENESAS_RZG2LWDT) += rzg2l_wdt.o
>   obj-$(CONFIG_ASPEED_WATCHDOG) += aspeed_wdt.o
>   obj-$(CONFIG_STM32_WATCHDOG) += stm32_iwdg.o
> diff --git a/drivers/watchdog/rzn1_wdt.c b/drivers/watchdog/rzn1_wdt.c
> new file mode 100644
> index 000000000000..fa32716727b7
> --- /dev/null
> +++ b/drivers/watchdog/rzn1_wdt.c
> @@ -0,0 +1,203 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Renesas RZ/N1 Watchdog timer.
> + * This is a 12-bit timer driver from a (62.5/16384) MHz clock. It can't even
> + * cope with 2 seconds.
> + *
> + * Copyright 2018 Renesas Electronics Europe Ltd.
> + *
> + * Derived from Ralink RT288x watchdog timer.
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/interrupt.h>
> +#include <linux/kernel.h>
> +#include <linux/module.h>
> +#include <linux/of_address.h>
> +#include <linux/of_irq.h>
> +#include <linux/platform_device.h>
> +#include <linux/reboot.h>
> +#include <linux/watchdog.h>
> +
> +#define DEFAULT_TIMEOUT		60
> +
> +#define RZN1_WDT_RETRIGGER			0x0
> +#define RZN1_WDT_RETRIGGER_RELOAD_VAL		0
> +#define RZN1_WDT_RETRIGGER_RELOAD_VAL_MASK	0xfff
> +#define RZN1_WDT_RETRIGGER_PRESCALE		BIT(12)
> +#define RZN1_WDT_RETRIGGER_ENABLE		BIT(13)
> +#define RZN1_WDT_RETRIGGER_WDSI			(0x2 << 14)
> +
> +#define RZN1_WDT_PRESCALER			16384
> +#define RZN1_WDT_MAX				4095
> +
> +struct rzn1_watchdog {
> +	struct watchdog_device		wdtdev;
> +	void __iomem			*base;
> +	unsigned long			clk_rate;

Nit: Whenever clk_rate is used, it is divided by 1000.
It might be better to store and use clk_rate_khz instead.

Guenter