Re: [PATCH v2] watchdog: ixp4xx: Rewrite driver to use core

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

On Tue, Jul 20, 2021 at 05:45:11PM +0200, Linus Walleij wrote:
> This rewrites the IXP4xx watchdog driver as follows:
> 
> - Spawn the watchdog driver as a platform device from the timer
>   driver. It's one device in the hardware, and the fact that
>   Linux splits the handling into two different devices is
>   a Linux pecularity, and thus it becomes a Linux pecularity
>   to spawn a separate watchdog driver.
> 
> - Spawn the watchdog driver from the timer driver at probe().
>   This is well after the timer driver as actually registered and
>   started and we know the register base is available.
> 
> - Instead of looping back callbacks to the timer drivers for all
>   watchdog calls, pass the register base to the watchdog driver
>   and manage the registers there. The two drivers aren't even
>   interested in the same register so the spinlock is totally
>   surplus, delete it.
> 
> - Replace pretty much all of the content in the watchdog driver
>   with a simple, modern watchdog driver utilizing the watchdog
>   core instead of registering its own misc device and ioctl()
>   handling.
> 
> - Drop module parameters as the same already exist in the
>   watchdog core.
> 
> What remains is a slim elegant (IMO) watchdog driver using the
> watchdog core, spawning from device tree or boardfile alike.
> 
> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
> ---
> ChangeLog v1->v2:
> - Pull out dirty patches underneath this patch. Tested on a
>   clean v5.14-rc1, sorry for the mess :(
> - Drop tick rate from the timer driver - was only used by this
>   watchdog after all.
> - Retrieve a clock from the parent to get rate if possible,
>   fallback to a default clock rate if not. Prepare and
>   enable the clock.
> - Add a devres hook to disable the clock after use.
> - Drop pointless platfrom_set_drvdata()
> - Put a more technically correct print at end of probe.
> Merge path: I expect this to be merged through the watchdog
> subsystem once the timer maintainers are happy with the patch,
> so Daniel or tglx: once you approve the patch please ACK this.
> ---
>  drivers/clocksource/timer-ixp4xx.c |  48 +++--
>  drivers/watchdog/Kconfig           |   3 +-
>  drivers/watchdog/ixp4xx_wdt.c      | 282 ++++++++++++-----------------
>  3 files changed, 157 insertions(+), 176 deletions(-)
> 
> diff --git a/drivers/clocksource/timer-ixp4xx.c b/drivers/clocksource/timer-ixp4xx.c
> index 9396745e1c17..cbb184953510 100644
> --- a/drivers/clocksource/timer-ixp4xx.c
> +++ b/drivers/clocksource/timer-ixp4xx.c
> @@ -18,6 +18,7 @@
>  #include <linux/delay.h>
>  #include <linux/of_address.h>
>  #include <linux/of_irq.h>
> +#include <linux/platform_device.h>
>  /* Goes away with OF conversion */
>  #include <linux/platform_data/timer-ixp4xx.h>
>  
> @@ -29,9 +30,6 @@
>  #define IXP4XX_OSRT1_OFFSET	0x08  /* Timer 1 Reload */
>  #define IXP4XX_OST2_OFFSET	0x0C  /* Timer 2 Timestamp */
>  #define IXP4XX_OSRT2_OFFSET	0x10  /* Timer 2 Reload */
> -#define IXP4XX_OSWT_OFFSET	0x14  /* Watchdog Timer */
> -#define IXP4XX_OSWE_OFFSET	0x18  /* Watchdog Enable */
> -#define IXP4XX_OSWK_OFFSET	0x1C  /* Watchdog Key */
>  #define IXP4XX_OSST_OFFSET	0x20  /* Timer Status */
>  
>  /*
> @@ -45,17 +43,10 @@
>  #define IXP4XX_OSST_TIMER_1_PEND	0x00000001
>  #define IXP4XX_OSST_TIMER_2_PEND	0x00000002
>  #define IXP4XX_OSST_TIMER_TS_PEND	0x00000004
> -#define IXP4XX_OSST_TIMER_WDOG_PEND	0x00000008
> -#define IXP4XX_OSST_TIMER_WARM_RESET	0x00000010
> -
> -#define	IXP4XX_WDT_KEY			0x0000482E
> -#define	IXP4XX_WDT_RESET_ENABLE		0x00000001
> -#define	IXP4XX_WDT_IRQ_ENABLE		0x00000002
> -#define	IXP4XX_WDT_COUNT_ENABLE		0x00000004
> +/* Remaining registers are for the watchdog and defined in the watchdog driver */
>  
>  struct ixp4xx_timer {
>  	void __iomem *base;
> -	unsigned int tick_rate;
>  	u32 latch;
>  	struct clock_event_device clkevt;
>  #ifdef CONFIG_ARM
> @@ -181,7 +172,6 @@ static __init int ixp4xx_timer_register(void __iomem *base,
>  	if (!tmr)
>  		return -ENOMEM;
>  	tmr->base = base;
> -	tmr->tick_rate = timer_freq;
>  
>  	/*
>  	 * The timer register doesn't allow to specify the two least
> @@ -239,6 +229,40 @@ static __init int ixp4xx_timer_register(void __iomem *base,
>  	return 0;
>  }
>  
> +static struct platform_device ixp4xx_watchdog_device = {
> +	.name = "ixp4xx-watchdog",
> +	.id = -1,
> +};
> +
> +/*
> + * This probe gets called after the timer is already up and running. The main
> + * function on this platform is to spawn the watchdog device as a child.
> + */
> +static int ixp4xx_timer_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +
> +	/* Pass the base address as platform data and nothing else */
> +	ixp4xx_watchdog_device.dev.platform_data = local_ixp4xx_timer->base;
> +	ixp4xx_watchdog_device.dev.parent = dev;
> +	return platform_device_register(&ixp4xx_watchdog_device);
> +}
> +
> +static const struct of_device_id ixp4xx_timer_dt_id[] = {
> +	{ .compatible = "intel,ixp4xx-timer", },
> +	{ /* sentinel */ },
> +};
> +
> +static struct platform_driver ixp4xx_timer_driver = {
> +	.probe  = ixp4xx_timer_probe,
> +	.driver = {
> +		.name = "ixp4xx-timer",
> +		.of_match_table = ixp4xx_timer_dt_id,
> +		.suppress_bind_attrs = true,
> +	},
> +};
> +builtin_platform_driver(ixp4xx_timer_driver);
> +
>  /**
>   * ixp4xx_timer_setup() - Timer setup function to be called from boardfiles
>   * @timerbase: physical base of timer block
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index 546dfc1e2349..33c97726144a 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -486,7 +486,8 @@ config FTWDT010_WATCHDOG
>  
>  config IXP4XX_WATCHDOG
>  	tristate "IXP4xx Watchdog"
> -	depends on ARCH_IXP4XX
> +	depends on ARCH_IXP4XX || COMPILE_TEST

x86_64:allmodconfig:

drivers/watchdog/ixp4xx_wdt.c: In function ‘ixp4xx_wdt_probe’:
drivers/watchdog/ixp4xx_wdt.c:117:8: error: implicit declaration of function ‘read_cpuid_id’

You'd have to move the CPU check into the timer code to
be able to enable COMPILE_TEST.

> +	select WATCHDOG_CORE
>  	help
>  	  Say Y here if to include support for the watchdog timer
>  	  in the Intel IXP4xx network processors. This driver can
> diff --git a/drivers/watchdog/ixp4xx_wdt.c b/drivers/watchdog/ixp4xx_wdt.c
> index aae29dcfaf11..9116ab097705 100644
> --- a/drivers/watchdog/ixp4xx_wdt.c
> +++ b/drivers/watchdog/ixp4xx_wdt.c
> @@ -1,220 +1,176 @@
> +// SPDX-License-Identifier: GPL-2.0-only
>  /*
>   * drivers/char/watchdog/ixp4xx_wdt.c
>   *
>   * Watchdog driver for Intel IXP4xx network processors
>   *
>   * Author: Deepak Saxena <dsaxena@plexity.net>
> + * Author: Linus Walleij <linus.walleij@linaro.org>
>   *
>   * Copyright 2004 (c) MontaVista, Software, Inc.
>   * Based on sa1100 driver, Copyright (C) 2000 Oleg Drokin <green@crimea.edu>
> - *
> - * This file is licensed under  the terms of the GNU General Public
> - * License version 2. This program is licensed "as is" without any
> - * warranty of any kind, whether express or implied.
>   */
>  
> -#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
> -
>  #include <linux/module.h>
> -#include <linux/moduleparam.h>
>  #include <linux/types.h>
>  #include <linux/kernel.h>
> -#include <linux/fs.h>
> -#include <linux/miscdevice.h>
> -#include <linux/of.h>
>  #include <linux/watchdog.h>
>  #include <linux/init.h>

Is this still needed ?

>  #include <linux/bitops.h>

I may be missing something, but I don't see any bit operations
in the driver.

> -#include <linux/uaccess.h>
> -#include <mach/hardware.h>
> +#include <linux/platform_device.h>
> +#include <linux/clk.h>
> +#include <linux/soc/ixp4xx/cpu.h>
> +
> +struct ixp4xx_wdt {
> +	struct watchdog_device wdd;
> +	void __iomem *base;
> +	unsigned long rate;
> +};
>  
> -static bool nowayout = WATCHDOG_NOWAYOUT;
> -static int heartbeat = 60;	/* (secs) Default is 1 minute */
> -static unsigned long wdt_status;
> -static unsigned long boot_status;
> -static DEFINE_SPINLOCK(wdt_lock);
> +/* Fallback if we do not have a clock for this */
> +#define IXP4XX_TIMER_FREQ 66666000

Please use

#define<space>IXP4XX_TIMER_FREQ<tab>66666000

>  
> -#define WDT_TICK_RATE (IXP4XX_PERIPHERAL_BUS_CLOCK * 1000000UL)
> +/* Registers after the timer registers */
> +#define IXP4XX_OSWT_OFFSET	0x14  /* Watchdog Timer */
> +#define IXP4XX_OSWE_OFFSET	0x18  /* Watchdog Enable */
> +#define IXP4XX_OSWK_OFFSET	0x1C  /* Watchdog Key */
> +#define IXP4XX_OSST_OFFSET	0x20  /* Timer Status */
>  
> -#define	WDT_IN_USE		0
> -#define	WDT_OK_TO_CLOSE		1
> +#define IXP4XX_OSST_TIMER_WDOG_PEND	0x00000008
> +#define IXP4XX_OSST_TIMER_WARM_RESET	0x00000010
> +#define	IXP4XX_WDT_KEY			0x0000482E
> +#define	IXP4XX_WDT_RESET_ENABLE		0x00000001
> +#define	IXP4XX_WDT_IRQ_ENABLE		0x00000002
> +#define	IXP4XX_WDT_COUNT_ENABLE		0x00000004
>  

Please use

#define<space>DEFINE<tab>value

> -static void wdt_enable(void)
> +static inline
> +struct ixp4xx_wdt *to_ixp4xx_wdt(struct watchdog_device *wdd)
>  {
> -	spin_lock(&wdt_lock);
> -	*IXP4XX_OSWK = IXP4XX_WDT_KEY;
> -	*IXP4XX_OSWE = 0;
> -	*IXP4XX_OSWT = WDT_TICK_RATE * heartbeat;
> -	*IXP4XX_OSWE = IXP4XX_WDT_COUNT_ENABLE | IXP4XX_WDT_RESET_ENABLE;
> -	*IXP4XX_OSWK = 0;
> -	spin_unlock(&wdt_lock);
> +	return container_of(wdd, struct ixp4xx_wdt, wdd);
>  }
>  
> -static void wdt_disable(void)
> +static int ixp4xx_wdt_start(struct watchdog_device *wdd)
>  {
> -	spin_lock(&wdt_lock);
> -	*IXP4XX_OSWK = IXP4XX_WDT_KEY;
> -	*IXP4XX_OSWE = 0;
> -	*IXP4XX_OSWK = 0;
> -	spin_unlock(&wdt_lock);
> -}
> +	struct ixp4xx_wdt *iwdt = to_ixp4xx_wdt(wdd);
>  
> -static int ixp4xx_wdt_open(struct inode *inode, struct file *file)
> -{
> -	if (test_and_set_bit(WDT_IN_USE, &wdt_status))
> -		return -EBUSY;
> +	__raw_writel(IXP4XX_WDT_KEY, iwdt->base + IXP4XX_OSWK_OFFSET);
> +	__raw_writel(0, iwdt->base + IXP4XX_OSWE_OFFSET);
> +	__raw_writel(wdd->timeout * iwdt->rate,
> +		     iwdt->base + IXP4XX_OSWT_OFFSET);
> +	__raw_writel(IXP4XX_WDT_COUNT_ENABLE | IXP4XX_WDT_RESET_ENABLE,
> +		     iwdt->base + IXP4XX_OSWE_OFFSET);
> +	__raw_writel(0, iwdt->base + IXP4XX_OSWK_OFFSET);
>  
> -	clear_bit(WDT_OK_TO_CLOSE, &wdt_status);
> -	wdt_enable();
> -	return stream_open(inode, file);
> -}
> -
> -static ssize_t
> -ixp4xx_wdt_write(struct file *file, const char *data, size_t len, loff_t *ppos)
> -{
> -	if (len) {
> -		if (!nowayout) {
> -			size_t i;
> -
> -			clear_bit(WDT_OK_TO_CLOSE, &wdt_status);
> -
> -			for (i = 0; i != len; i++) {
> -				char c;
> -
> -				if (get_user(c, data + i))
> -					return -EFAULT;
> -				if (c == 'V')
> -					set_bit(WDT_OK_TO_CLOSE, &wdt_status);
> -			}
> -		}
> -		wdt_enable();
> -	}
> -	return len;
> +	return 0;
>  }
>  
> -static const struct watchdog_info ident = {
> -	.options	= WDIOF_CARDRESET | WDIOF_MAGICCLOSE |
> -			  WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING,
> -	.identity	= "IXP4xx Watchdog",
> -};
> -
> -
> -static long ixp4xx_wdt_ioctl(struct file *file, unsigned int cmd,
> -							unsigned long arg)
> +static int ixp4xx_wdt_stop(struct watchdog_device *wdd)
>  {
> -	int ret = -ENOTTY;
> -	int time;
> -
> -	switch (cmd) {
> -	case WDIOC_GETSUPPORT:
> -		ret = copy_to_user((struct watchdog_info *)arg, &ident,
> -				   sizeof(ident)) ? -EFAULT : 0;
> -		break;
> -
> -	case WDIOC_GETSTATUS:
> -		ret = put_user(0, (int *)arg);
> -		break;
> -
> -	case WDIOC_GETBOOTSTATUS:
> -		ret = put_user(boot_status, (int *)arg);
> -		break;
> -
> -	case WDIOC_KEEPALIVE:
> -		wdt_enable();
> -		ret = 0;
> -		break;
> -
> -	case WDIOC_SETTIMEOUT:
> -		ret = get_user(time, (int *)arg);
> -		if (ret)
> -			break;
> +	struct ixp4xx_wdt *iwdt = to_ixp4xx_wdt(wdd);
>  
> -		if (time <= 0 || time > 60) {
> -			ret = -EINVAL;
> -			break;
> -		}
> +	__raw_writel(IXP4XX_WDT_KEY, iwdt->base + IXP4XX_OSWK_OFFSET);
> +	__raw_writel(0, iwdt->base + IXP4XX_OSWE_OFFSET);
> +	__raw_writel(0, iwdt->base + IXP4XX_OSWK_OFFSET);
>  
> -		heartbeat = time;
> -		wdt_enable();
> -		fallthrough;
> -
> -	case WDIOC_GETTIMEOUT:
> -		ret = put_user(heartbeat, (int *)arg);
> -		break;
> -	}
> -	return ret;
> +	return 0;
>  }
>  
> -static int ixp4xx_wdt_release(struct inode *inode, struct file *file)
> +static int ixp4xx_wdt_set_timeout(struct watchdog_device *wdd,
> +				  unsigned int timeout)
>  {
> -	if (test_bit(WDT_OK_TO_CLOSE, &wdt_status))
> -		wdt_disable();
> -	else
> -		pr_crit("Device closed unexpectedly - timer will not stop\n");
> -	clear_bit(WDT_IN_USE, &wdt_status);
> -	clear_bit(WDT_OK_TO_CLOSE, &wdt_status);
> +	wdd->timeout = timeout;
> +	if (watchdog_active(wdd))
> +		ixp4xx_wdt_start(wdd);
>  
>  	return 0;
>  }
>  
> -
> -static const struct file_operations ixp4xx_wdt_fops = {
> -	.owner		= THIS_MODULE,
> -	.llseek		= no_llseek,
> -	.write		= ixp4xx_wdt_write,
> -	.unlocked_ioctl	= ixp4xx_wdt_ioctl,
> -	.compat_ioctl	= compat_ptr_ioctl,
> -	.open		= ixp4xx_wdt_open,
> -	.release	= ixp4xx_wdt_release,
> +static const struct watchdog_ops ixp4xx_wdt_ops = {
> +	.start = ixp4xx_wdt_start,
> +	.stop = ixp4xx_wdt_stop,
> +	.set_timeout = ixp4xx_wdt_set_timeout,
> +	.owner = THIS_MODULE,
>  };
>  
> -static struct miscdevice ixp4xx_wdt_miscdev = {
> -	.minor		= WATCHDOG_MINOR,
> -	.name		= "watchdog",
> -	.fops		= &ixp4xx_wdt_fops,
> +static const struct watchdog_info ixp4xx_wdt_info = {
> +	.options = WDIOF_KEEPALIVEPING
> +		| WDIOF_MAGICCLOSE
> +		| WDIOF_SETTIMEOUT,
> +	.identity = KBUILD_MODNAME,
>  };
>  
> -static int __init ixp4xx_wdt_init(void)
> +/* Devres-handled clock disablement */
> +static void ixp4xx_clock_action(void *d)
> +{
> +	struct clk *clk = d;
> +
> +	clk_disable_unprepare(clk);

Oddly enough, while you can't call ixp4xx_clock_action() directly
with devm_add_action, you can call
	clk_disable_unprepare(d);
directly, and the extra variable isn't needed.

> +}
> +
> +static int ixp4xx_wdt_probe(struct platform_device *pdev)
>  {
> +	struct device *dev = &pdev->dev;
> +	struct ixp4xx_wdt *iwdt;
> +	struct clk *clk;
>  	int ret;
>  
> -	/*
> -	 * FIXME: we bail out on device tree boot but this really needs
> -	 * to be fixed in a nicer way: this registers the MDIO bus before
> -	 * even matching the driver infrastructure, we should only probe
> -	 * detected hardware.
> -	 */
> -	if (of_have_populated_dt())
> -		return -ENODEV;
>  	if (!(read_cpuid_id() & 0xf) && !cpu_is_ixp46x()) {
> -		pr_err("Rev. A0 IXP42x CPU detected - watchdog disabled\n");
> -
> +		dev_err(dev, "Rev. A0 IXP42x CPU detected - watchdog disabled\n");
>  		return -ENODEV;
>  	}
> -	boot_status = (*IXP4XX_OSST & IXP4XX_OSST_TIMER_WARM_RESET) ?
> -			WDIOF_CARDRESET : 0;
> -	ret = misc_register(&ixp4xx_wdt_miscdev);
> -	if (ret == 0)
> -		pr_info("timer heartbeat %d sec\n", heartbeat);
> -	return ret;
> -}
>  
> -static void __exit ixp4xx_wdt_exit(void)
> -{
> -	misc_deregister(&ixp4xx_wdt_miscdev);
> -}
> +	iwdt = devm_kzalloc(dev, sizeof(*iwdt), GFP_KERNEL);
> +	if (!iwdt)
> +		return -ENOMEM;
> +	iwdt->base = dev->platform_data;
>  
> +	/*
> +	 * Retrieve rate from a fixed clock from the device tree if
> +	 * the parent has that, else use the default clock rate.
> +	 */
> +	clk = devm_clk_get(dev->parent, NULL);
> +	if (!IS_ERR(clk)) {
> +		ret = clk_prepare_enable(clk);
> +		if (ret)
> +			return ret;
> +		ret = devm_add_action_or_reset(dev, ixp4xx_clock_action, clk);
> +		if (ret)
> +			return ret;
> +		iwdt->rate = clk_get_rate(clk);
> +	}
> +	if (!iwdt->rate)
> +		iwdt->rate = IXP4XX_TIMER_FREQ;
>  
> -module_init(ixp4xx_wdt_init);
> -module_exit(ixp4xx_wdt_exit);
> +	iwdt->wdd.info = &ixp4xx_wdt_info;
> +	iwdt->wdd.ops = &ixp4xx_wdt_ops;
> +	iwdt->wdd.min_timeout = 1;
> +	iwdt->wdd.max_timeout = U32_MAX / iwdt->rate;
> +	iwdt->wdd.parent = dev;
> +	/* Default to 60 seconds */
> +	iwdt->wdd.timeout = 60U;
> +	watchdog_init_timeout(&iwdt->wdd, 0, dev);
>  
> -MODULE_AUTHOR("Deepak Saxena <dsaxena@plexity.net>");
> -MODULE_DESCRIPTION("IXP4xx Network Processor Watchdog");
> +	if (__raw_readl(iwdt->base + IXP4XX_OSST_OFFSET) &
> +	    IXP4XX_OSST_TIMER_WARM_RESET)
> +		iwdt->wdd.bootstatus = WDIOF_CARDRESET;
> +
> +	ret = devm_watchdog_register_device(dev, &iwdt->wdd);
> +	if (ret)
> +		return ret;
> +
> +	dev_info(dev, "IXP4xx watchdog available\n");
>  
> -module_param(heartbeat, int, 0);
> -MODULE_PARM_DESC(heartbeat, "Watchdog heartbeat in seconds (default 60s)");
> +	return 0;
> +}
>  
> -module_param(nowayout, bool, 0);
> -MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started");
> +static struct platform_driver ixp4xx_wdt_driver = {
> +	.probe = ixp4xx_wdt_probe,
> +	.driver = {
> +		.name   = "ixp4xx-watchdog",
> +	},
> +};
> +module_platform_driver(ixp4xx_wdt_driver);
>  
> +MODULE_AUTHOR("Deepak Saxena <dsaxena@plexity.net>");
> +MODULE_DESCRIPTION("IXP4xx Network Processor Watchdog");
>  MODULE_LICENSE("GPL");
> -- 
> 2.31.1
>