Re: [PATCH 1/1] watchdog: repair pnx833x_wdt

From: Guenter Roeck
Date: Thu Oct 15 2020 - 12:34:00 EST

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In reply to: Sergey Yasinsky: "[PATCH 1/1] watchdog: repair pnx833x_wdt"
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On Wed, Oct 14, 2020 at 05:56:32PM +0300, Sergey Yasinsky wrote:
> Using watchdog core functions instead of miscdevice.
>
This is not a repair, this is a convertion to use the
watchdog core (which also happens to fix a compile error).

The driver should also be converted to a platform device,
and be instantiated from arch/mips/pnx833x/common/platform.c
like the various other drivers in that syste,. As currently
written, the driver would be instantiated whenever it is built
into an image or loaded, which could result in a crash if
it is loaded on a system where the IO addresses it uses are
not mapped.

More comments inline.

Thanks,
Guenter

> Signed-off-by: Sergey Yasinsky <seregajsv@xxxxxxxxx>
> ---
> drivers/watchdog/Kconfig | 2 +-
> drivers/watchdog/pnx833x_wdt.c | 219 ++++++++-------------------------
> 2 files changed, 53 insertions(+), 168 deletions(-)
>
> diff --git a/drivers/watchdog/Kconfig b/drivers/watchdog/Kconfig
> index ab7aad5a1e69..e9b86dbbb8fa 100644
> --- a/drivers/watchdog/Kconfig
> +++ b/drivers/watchdog/Kconfig
> @@ -1686,7 +1686,7 @@ config WDT_MTX1
> config PNX833X_WDT
> tristate "PNX833x Hardware Watchdog"
> depends on SOC_PNX8335
> - depends on BROKEN
> + select WATCHDOG_CORE
> help
> Hardware driver for the PNX833x's watchdog. This is a
> watchdog timer that will reboot the machine after a programmable
> diff --git a/drivers/watchdog/pnx833x_wdt.c b/drivers/watchdog/pnx833x_wdt.c
> index 4097d076aab8..4ec852c423da 100644
> --- a/drivers/watchdog/pnx833x_wdt.c
> +++ b/drivers/watchdog/pnx833x_wdt.c
> @@ -17,21 +17,11 @@
>
> #include <linux/module.h>
> #include <linux/moduleparam.h>
> -#include <linux/types.h>
> -#include <linux/kernel.h>
> -#include <linux/fs.h>
> -#include <linux/mm.h>
> -#include <linux/miscdevice.h>
> #include <linux/watchdog.h>
> -#include <linux/notifier.h>
> -#include <linux/reboot.h>
> -#include <linux/init.h>
> #include <asm/mach-pnx833x/pnx833x.h>
>
> -#define WATCHDOG_TIMEOUT 30 /* 30 sec Maximum timeout */
> +#define WATCHDOG_DEFAULT_TIMEOUT 30
> #define WATCHDOG_COUNT_FREQUENCY 68000000U /* Watchdog counts at 68MHZ. */
> -#define PNX_WATCHDOG_TIMEOUT (WATCHDOG_TIMEOUT * WATCHDOG_COUNT_FREQUENCY)
> -#define PNX_TIMEOUT_VALUE 2040000000U
>
> /** CONFIG block */
> #define PNX833X_CONFIG (0x07000U)
> @@ -43,40 +33,37 @@
> #define PNX833X_RESET (0x08000U)
> #define PNX833X_RESET_CONFIG (0x08)
>
> -static int pnx833x_wdt_alive;
> +struct pnx833x_wdt {
> + struct watchdog_device wdd;
> +};

This structure is unnecessary. You can use struct
watchdog_device directly.

>
> -/* Set default timeout in MHZ.*/
> -static int pnx833x_wdt_timeout = PNX_WATCHDOG_TIMEOUT;
> +/* Set default timeout */
> +static int pnx833x_wdt_timeout = WATCHDOG_DEFAULT_TIMEOUT;

The default should be set in struct watchdog_device.timeout,
and the module parameter should (only) be used to override it,
and be initialized with 0. More on that see below.

> module_param(pnx833x_wdt_timeout, int, 0);
> -MODULE_PARM_DESC(timeout, "Watchdog timeout in Mhz. (68Mhz clock), default="
> - __MODULE_STRING(PNX_TIMEOUT_VALUE) "(30 seconds).");
> +MODULE_PARM_DESC(timeout, "Watchdog timeout in seconds (default="
> + __MODULE_STRING(WATCHDOG_DEFAULT_TIMEOUT) ")");
>
> static bool nowayout = WATCHDOG_NOWAYOUT;
> module_param(nowayout, bool, 0);
> MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default="
> __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
>
> -#define START_DEFAULT 1
> -static int start_enabled = START_DEFAULT;
> -module_param(start_enabled, int, 0);
> -MODULE_PARM_DESC(start_enabled, "Watchdog is started on module insertion "
> - "(default=" __MODULE_STRING(START_DEFAULT) ")");

Why drop this ? Someone may use it, and the watchdog core
supports it.

> -
> -static void pnx833x_wdt_start(void)
> +static int pnx833x_wdt_start(struct watchdog_device *wdd)
> {
> /* Enable watchdog causing reset. */
> PNX833X_REG(PNX833X_RESET + PNX833X_RESET_CONFIG) |= 0x1;
> /* Set timeout.*/
> - PNX833X_REG(PNX833X_CONFIG +
> - PNX833X_CONFIG_CPU_WATCHDOG_COMPARE) = pnx833x_wdt_timeout;
> + PNX833X_REG(PNX833X_CONFIG + PNX833X_CONFIG_CPU_WATCHDOG_COMPARE) =
> + wdd->timeout * WATCHDOG_COUNT_FREQUENCY;
> /* Enable watchdog. */
> PNX833X_REG(PNX833X_CONFIG +
> PNX833X_CONFIG_CPU_COUNTERS_CONTROL) |= 0x1;
>
> pr_info("Started watchdog timer\n");

Please drop this message.

> + return 0;
> }
>
> -static void pnx833x_wdt_stop(void)
> +static int pnx833x_wdt_stop(struct watchdog_device *wdd)
> {
> /* Disable watchdog causing reset. */
> PNX833X_REG(PNX833X_RESET + PNX833X_CONFIG) &= 0xFFFFFFFE;
> @@ -85,149 +72,54 @@ static void pnx833x_wdt_stop(void)
> PNX833X_CONFIG_CPU_COUNTERS_CONTROL) &= 0xFFFFFFFE;
>
> pr_info("Stopped watchdog timer\n");

Please drop this message (if you think it is useful for some reason,
make it a debug message).

> -}
> -
> -static void pnx833x_wdt_ping(void)
> -{
> - PNX833X_REG(PNX833X_CONFIG +
> - PNX833X_CONFIG_CPU_WATCHDOG_COMPARE) = pnx833x_wdt_timeout;
> -}
> -
> -/*
> - * Allow only one person to hold it open
> - */
> -static int pnx833x_wdt_open(struct inode *inode, struct file *file)
> -{
> - if (test_and_set_bit(0, &pnx833x_wdt_alive))
> - return -EBUSY;
> -
> - if (nowayout)
> - __module_get(THIS_MODULE);
> -
> - /* Activate timer */
> - if (!start_enabled)
> - pnx833x_wdt_start();
> -
> - pnx833x_wdt_ping();
> -
> - pr_info("Started watchdog timer\n");
> -
> - return stream_open(inode, file);
> -}
> -
> -static int pnx833x_wdt_release(struct inode *inode, struct file *file)
> -{
> - /* Shut off the timer.
> - * Lock it in if it's a module and we defined ...NOWAYOUT */
> - if (!nowayout)
> - pnx833x_wdt_stop(); /* Turn the WDT off */
> -
> - clear_bit(0, &pnx833x_wdt_alive);
> return 0;
> }
>
> -static ssize_t pnx833x_wdt_write(struct file *file, const char *data, size_t len, loff_t *ppos)
> +static int pnx833x_wdt_ping(struct watchdog_device *wdd)
> {
> - /* Refresh the timer. */
> - if (len)
> - pnx833x_wdt_ping();
> + PNX833X_REG(PNX833X_CONFIG + PNX833X_CONFIG_CPU_WATCHDOG_COMPARE) =
> + wdd->timeout * WATCHDOG_COUNT_FREQUENCY;
>
> - return len;
> + return 0;
> }
>
> -static long pnx833x_wdt_ioctl(struct file *file, unsigned int cmd,
> - unsigned long arg)
> +static int pnx833x_wdt_set_timeout(struct watchdog_device *wdd, unsigned int t)
> {
> - int options, new_timeout = 0;
> - uint32_t timeout, timeout_left = 0;
> -
> - static const struct watchdog_info ident = {
> - .options = WDIOF_KEEPALIVEPING | WDIOF_SETTIMEOUT,
> - .firmware_version = 0,
> - .identity = "Hardware Watchdog for PNX833x",
> - };
> -
> - switch (cmd) {
> - default:
> - return -ENOTTY;
> -
> - case WDIOC_GETSUPPORT:
> - if (copy_to_user((struct watchdog_info *)arg,
> - &ident, sizeof(ident)))
> - return -EFAULT;
> - return 0;
> -
> - case WDIOC_GETSTATUS:
> - case WDIOC_GETBOOTSTATUS:
> - return put_user(0, (int *)arg);
> -
> - case WDIOC_SETOPTIONS:
> - if (get_user(options, (int *)arg))
> - return -EFAULT;
> -
> - if (options & WDIOS_DISABLECARD)
> - pnx833x_wdt_stop();
> -
> - if (options & WDIOS_ENABLECARD)
> - pnx833x_wdt_start();
> -
> - return 0;
> -
> - case WDIOC_KEEPALIVE:
> - pnx833x_wdt_ping();
> - return 0;
> -
> - case WDIOC_SETTIMEOUT:
> - {
> - if (get_user(new_timeout, (int *)arg))
> - return -EFAULT;
> -
> - pnx833x_wdt_timeout = new_timeout;
> - PNX833X_REG(PNX833X_CONFIG +
> - PNX833X_CONFIG_CPU_WATCHDOG_COMPARE) = new_timeout;
> - return put_user(new_timeout, (int *)arg);
> - }
> -
> - case WDIOC_GETTIMEOUT:
> - timeout = PNX833X_REG(PNX833X_CONFIG +
> - PNX833X_CONFIG_CPU_WATCHDOG_COMPARE);
> - return put_user(timeout, (int *)arg);
> -
> - case WDIOC_GETTIMELEFT:
> - timeout_left = PNX833X_REG(PNX833X_CONFIG +
> - PNX833X_CONFIG_CPU_WATCHDOG);
> - return put_user(timeout_left, (int *)arg);
> -
> - }
> + PNX833X_REG(PNX833X_CONFIG + PNX833X_CONFIG_CPU_WATCHDOG_COMPARE) =
> + t * WATCHDOG_COUNT_FREQUENCY;
> + wdd->timeout = t;
> + return 0;
> }
>
> -static int pnx833x_wdt_notify_sys(struct notifier_block *this,
> - unsigned long code, void *unused)
> +static unsigned int pnx833x_wdt_get_timeleft(struct watchdog_device *wdd)
> {
> - if (code == SYS_DOWN || code == SYS_HALT)
> - pnx833x_wdt_stop(); /* Turn the WDT off */
> + unsigned int timeout = PNX833X_REG(PNX833X_CONFIG +
> + PNX833X_CONFIG_CPU_WATCHDOG_COMPARE);
> + unsigned int curval = PNX833X_REG(PNX833X_CONFIG +
> + PNX833X_CONFIG_CPU_WATCHDOG);
>
> - return NOTIFY_DONE;
> + return (timeout - curval) / WATCHDOG_COUNT_FREQUENCY;
> }
>
> -static const struct file_operations pnx833x_wdt_fops = {
> - .owner = THIS_MODULE,
> - .llseek = no_llseek,
> - .write = pnx833x_wdt_write,
> - .unlocked_ioctl = pnx833x_wdt_ioctl,
> - .compat_ioctl = compat_ptr_ioctl,
> - .open = pnx833x_wdt_open,
> - .release = pnx833x_wdt_release,
> +static const struct watchdog_info pnx833x_wdt_ident = {
> + .identity = "PNX833x Watchdog Timer",
> + .options = WDIOF_SETTIMEOUT | WDIOF_KEEPALIVEPING | WDIOF_MAGICCLOSE
> };
>
> -static struct miscdevice pnx833x_wdt_miscdev = {
> - .minor = WATCHDOG_MINOR,
> - .name = "watchdog",
> - .fops = &pnx833x_wdt_fops,
> +static struct watchdog_ops pnx833x_wdt_ops = {
> + .owner = THIS_MODULE,
> + .start = pnx833x_wdt_start,
> + .stop = pnx833x_wdt_stop,
> + .ping = pnx833x_wdt_ping,
> + .set_timeout = pnx833x_wdt_set_timeout,
> + .get_timeleft = pnx833x_wdt_get_timeleft,
> };
>
> -static struct notifier_block pnx833x_wdt_notifier = {
> - .notifier_call = pnx833x_wdt_notify_sys,
> +struct pnx833x_wdt pnx833x_wdd = {

This should be static. Actually, it should be dynamically
allocated, which is easy if/when the driver is converted
to a platform driver.

> + .wdd = {
> + .info = &pnx833x_wdt_ident,
> + .ops = &pnx833x_wdt_ops,
> + },
> };
>
> static int __init watchdog_init(void)
> @@ -237,36 +129,29 @@ static int __init watchdog_init(void)
> /* Lets check the reason for the reset.*/
> cause = PNX833X_REG(PNX833X_RESET);
> /*If bit 31 is set then watchdog was cause of reset.*/
> - if (cause & 0x80000000) {
> + if (cause & 0x80000000)
> pr_info("The system was previously reset due to the watchdog firing - please investigate...\n");
> - }

This should set WDIOF_CARDRESET, and I would suggest to drop the message
(no one is going to read it anyway).

>
> - ret = register_reboot_notifier(&pnx833x_wdt_notifier);
> - if (ret) {
> - pr_err("cannot register reboot notifier (err=%d)\n", ret);
> - return ret;
> - }

The above can be handled in the watchdog core if needed.

> + pnx833x_wdd.wdd.max_timeout = U32_MAX / WATCHDOG_COUNT_FREQUENCY;

Also set min_timeout to 1.

> + pnx833x_wdd.wdd.timeout = pnx833x_wdt_timeout;
> + if (pnx833x_wdd.wdd.timeout > pnx833x_wdd.wdd.max_timeout)
> + pnx833x_wdd.wdd.timeout = pnx833x_wdd.wdd.max_timeout;
>
pnx833x_wdd.wdd.timeout should be initialized with the
default, and the new value should be set with
watchdog_init_timeout(&wdd, pnx833x_wdt_timeout, NULL);

This also takes care of error handling.

> - ret = misc_register(&pnx833x_wdt_miscdev);
> + watchdog_set_nowayout(&pnx833x_wdd.wdd, nowayout);
> + ret = watchdog_register_device(&pnx833x_wdd.wdd);
> if (ret) {
> - pr_err("cannot register miscdev on minor=%d (err=%d)\n",
> - WATCHDOG_MINOR, ret);
> - unregister_reboot_notifier(&pnx833x_wdt_notifier);
> + pr_err("Failed to register watchdog device");
> return ret;
> }
>
> pr_info("Hardware Watchdog Timer for PNX833x: Version 0.1\n");

Sure this is not anymore version 0.1. I'd suggest to drop
the version information since it is useless.
>
> - if (start_enabled)
> - pnx833x_wdt_start();
> -

As mentioned above, I don't see a reason for dropping this.
The driver can call it prior to watchdog registration, and
set WDOG_HW_RUNNING in wdd->status.

> return 0;
> }
>
> static void __exit watchdog_exit(void)
> {
> - misc_deregister(&pnx833x_wdt_miscdev);
> - unregister_reboot_notifier(&pnx833x_wdt_notifier);
> + watchdog_unregister_device(&pnx833x_wdd.wdd);
> }
>
> module_init(watchdog_init);
> --
> 2.26.2
>

Next message: Eric Biggers: "Re: [PATCH v6 35/80] docs: fs: fscrypt.rst: get rid of :c:type: tags"
Previous message: Karol Herbst: "Re: [Nouveau] [PATCH RFC] drm/nouveau: fix memory leak in nvkm_iccsense_oneinit"
In reply to: Sergey Yasinsky: "[PATCH 1/1] watchdog: repair pnx833x_wdt"
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