Re: [PATCH 1/4] watchdog: at91sam9_wdt: better watchdog support
From: Guenter Roeck
Date: Thu Oct 03 2013 - 13:31:19 EST
On Thu, Oct 03, 2013 at 02:19:18PM +0200, Boris BREZILLON wrote:
> The at91sam9 watchdog timer can only be configured once, and the current
> implementation tries to configure it in a static way:
> - 2 seconds timeout
> - wdt restart every 500ms
>
> If the timer has already been configured with different values, it returns an
> error and do not create any watchdog device.
>
> This is not critical if the watchdog is disabled, but if it has been enabled with
> different timeout values it will lead to a SoC reset.
>
> This patch series tries to address this issue by adapting the heartbeat value
> according the WDT timer config:
> - it first tries to configure the timer as requested.
> - if it fails it fallbacks to the current config, adapting its heartbeat timer
> to the needs
>
> This patch series also move to a dynamically allocated at91wdt device instead
> of the static instance.
>
> It adds a new at91 wdt type: software. This new type make use of the at91 wdt
> interrupt to trigger a software reboot.
>
> Finally it adds several properties to the device tree bindings.
>
> Signed-off-by: Boris BREZILLON <b.brezillon@xxxxxxxxxxx>
Hi Boris,
deeper dive this time ...
> ---
> drivers/watchdog/at91sam9_wdt.c | 300 ++++++++++++++++++++++++++++-----------
> 1 file changed, 217 insertions(+), 83 deletions(-)
>
> diff --git a/drivers/watchdog/at91sam9_wdt.c b/drivers/watchdog/at91sam9_wdt.c
> index be37dde..8f44528 100644
> --- a/drivers/watchdog/at91sam9_wdt.c
> +++ b/drivers/watchdog/at91sam9_wdt.c
> @@ -19,11 +19,13 @@
>
> #include <linux/errno.h>
> #include <linux/init.h>
> +#include <linux/interrupt.h>
> #include <linux/io.h>
> #include <linux/kernel.h>
> #include <linux/module.h>
> #include <linux/moduleparam.h>
> #include <linux/platform_device.h>
> +#include <linux/reboot.h>
> #include <linux/types.h>
> #include <linux/watchdog.h>
> #include <linux/jiffies.h>
> @@ -31,22 +33,33 @@
> #include <linux/bitops.h>
> #include <linux/uaccess.h>
> #include <linux/of.h>
> +#include <linux/of_irq.h>
>
> #include "at91sam9_wdt.h"
>
> #define DRV_NAME "AT91SAM9 Watchdog"
>
> -#define wdt_read(field) \
> - __raw_readl(at91wdt_private.base + field)
> -#define wdt_write(field, val) \
> - __raw_writel((val), at91wdt_private.base + field)
> +#define wdt_read(wdt, field) \
> + __raw_readl((wdt)->base + (field))
> +#define wdt_write(wtd, field, val) \
> + __raw_writel((val), (wdt)->base + (field))
>
> /* AT91SAM9 watchdog runs a 12bit counter @ 256Hz,
> * use this to convert a watchdog
> * value from/to milliseconds.
> */
> -#define ms_to_ticks(t) (((t << 8) / 1000) - 1)
> -#define ticks_to_ms(t) (((t + 1) * 1000) >> 8)
> +#define ticks_to_hz_rounddown(t) ((((t) + 1) * HZ) >> 8)
> +#define ticks_to_hz_roundup(t) (((((t) + 1) * HZ) + 255) >> 8)
> +#define ticks_to_secs(t) (((t) + 1) >> 8)
> +#define secs_to_ticks(s) (((s) << 8) - 1)
> +
> +#define WDT_MR_RESET 0x3FFF2FFF
> +
> +/* Watchdog max counter value in ticks */
> +#define WDT_COUNTER_MAX_TICKS 0xFFF
> +
> +/* Watchdog max delta/value in secs */
> +#define WDT_COUNTER_MAX_SECS ticks_to_secs(WDT_COUNTER_MAX_TICKS)
>
> /* Hardware timeout in seconds */
> #define WDT_HW_TIMEOUT 2
> @@ -66,23 +79,40 @@ module_param(nowayout, bool, 0);
> MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started "
> "(default=" __MODULE_STRING(WATCHDOG_NOWAYOUT) ")");
>
> -static struct watchdog_device at91_wdt_dev;
> -static void at91_ping(unsigned long data);
> -
> -static struct {
> +#define to_wdt(wdd) container_of(wdd, struct at91wdt, wdd)
> +struct at91wdt {
> + struct watchdog_device wdd;
> void __iomem *base;
> unsigned long next_heartbeat; /* the next_heartbeat for the timer */
> struct timer_list timer; /* The timer that pings the watchdog */
> -} at91wdt_private;
> + u32 mr;
> + u32 mr_mask;
> + unsigned long heartbeat; /* WDT heartbeat in jiffies */
> + bool nowayout;
> + unsigned int irq;
> +};
>
> /* ......................................................................... */
>
> +static irqreturn_t wdt_interrupt(int irq, void *dev_id)
> +{
> + struct at91wdt *wdt = (struct at91wdt *)dev_id;
> +
> + if (wdt_read(wdt, AT91_WDT_SR)) {
> + pr_crit("at91sam9 WDT software reset\n");
> + emergency_restart();
> + pr_crit("Reboot didn't ?????\n");
> + }
> +
> + return IRQ_HANDLED;
> +}
> +
> /*
> * Reload the watchdog timer. (ie, pat the watchdog)
> */
> -static inline void at91_wdt_reset(void)
> +static inline void at91_wdt_reset(struct at91wdt *wdt)
> {
> - wdt_write(AT91_WDT_CR, AT91_WDT_KEY | AT91_WDT_WDRSTT);
> + wdt_write(wdt, AT91_WDT_CR, AT91_WDT_KEY | AT91_WDT_WDRSTT);
> }
>
> /*
> @@ -90,26 +120,20 @@ static inline void at91_wdt_reset(void)
> */
> static void at91_ping(unsigned long data)
> {
> - if (time_before(jiffies, at91wdt_private.next_heartbeat) ||
> - (!watchdog_active(&at91_wdt_dev))) {
> - at91_wdt_reset();
> - mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
> + struct at91wdt *wdt = (struct at91wdt *)data;
> + if (time_before(jiffies, wdt->next_heartbeat) ||
> + !watchdog_active(&wdt->wdd)) {
> + at91_wdt_reset(wdt);
> + mod_timer(&wdt->timer, jiffies + wdt->heartbeat);
> } else
> pr_crit("I will reset your machine !\n");
> }
>
> static int at91_wdt_ping(struct watchdog_device *wdd)
> {
> + struct at91wdt *wdt = to_wdt(wdd);
> /* calculate when the next userspace timeout will be */
> - at91wdt_private.next_heartbeat = jiffies + wdd->timeout * HZ;
> - return 0;
> -}
> -
> -static int at91_wdt_start(struct watchdog_device *wdd)
> -{
> - /* calculate the next userspace timeout and modify the timer */
> - at91_wdt_ping(wdd);
> - mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
> + wdt->next_heartbeat = jiffies + wdd->timeout * HZ;
> return 0;
> }
>
> @@ -125,36 +149,84 @@ static int at91_wdt_set_timeout(struct watchdog_device *wdd, unsigned int new_ti
at91_wdt_set_timeout only sets the new timeout but does not update
next_heartbeat. That is ok if the timeout decreases, but if it is
increased (say, from 1 second to 1 minute) it might result in a missed
ping as userspace will subsequently believe that the new (larger)
timeout was accepted by the driver. So I think you should also call
at91_wdt_ping here or set wdt->next_heartbeat directly.
> return 0;
> }
>
> -/*
> - * Set the watchdog time interval in 1/256Hz (write-once)
> - * Counter is 12 bit.
> - */
> -static int at91_wdt_settimeout(unsigned int timeout)
> +static int at91_wdt_init(struct platform_device *pdev, struct at91wdt *wdt)
> {
> - unsigned int reg;
> - unsigned int mr;
> -
> - /* Check if disabled */
> - mr = wdt_read(AT91_WDT_MR);
> - if (mr & AT91_WDT_WDDIS) {
> - pr_err("sorry, watchdog is disabled\n");
> - return -EIO;
> + u32 tmp;
> + u32 delta;
> + u32 value;
> + int err;
> + u32 mask = wdt->mr_mask;
> + unsigned long min_heartbeat = 1;
> +
> + tmp = wdt_read(wdt, AT91_WDT_MR);
> + if ((tmp & mask) != (wdt->mr & mask)) {
> + if (tmp == WDT_MR_RESET) {
> + wdt_write(wdt, AT91_WDT_MR, wdt->mr);
> + tmp = wdt_read(wdt, AT91_WDT_MR);
> + }
> }
>
> - /*
> - * All counting occurs at SLOW_CLOCK / 128 = 256 Hz
> - *
> - * Since WDV is a 12-bit counter, the maximum period is
> - * 4096 / 256 = 16 seconds.
> - */
> - reg = AT91_WDT_WDRSTEN /* causes watchdog reset */
> - /* | AT91_WDT_WDRPROC causes processor reset only */
> - | AT91_WDT_WDDBGHLT /* disabled in debug mode */
> - | AT91_WDT_WDD /* restart at any time */
> - | (timeout & AT91_WDT_WDV); /* timer value */
> - wdt_write(AT91_WDT_MR, reg);
> + if (tmp & AT91_WDT_WDDIS) {
> + if (wdt->mr & AT91_WDT_WDDIS)
> + return 0;
> + dev_err(wdt->wdd.parent, "watchdog is disabled\n");
Took me a while to get why you use "wdt->wdd.parent" :).
I would just have passed the 'dev' argument. Your call, though.
> + return -EINVAL;
> + }
> +
> + value = tmp & AT91_WDT_WDV;
> + delta = (tmp & AT91_WDT_WDD) >> 16;
> +
> + if (delta < value)
> + min_heartbeat = ticks_to_hz_roundup(value - delta);
> +
> + wdt->heartbeat = ticks_to_hz_rounddown(value);
> + if (!wdt->heartbeat) {
> + dev_err(wdt->wdd.parent,
> + "heartbeat is too small for the system to handle it correctly\n");
> + return -EINVAL;
> + }
> +
> + if (wdt->heartbeat < min_heartbeat + 3) {
> + wdt->heartbeat = min_heartbeat;
> + dev_warn(wdt->wdd.parent,
> + "min heartbeat and max heartbeat might be too close for the system to handle it correctly\n");
> + if (wdt->heartbeat < 4)
> + dev_warn(wdt->wdd.parent,
> + "heartbeat might be too small for the system to handle it correctly\n");
> + } else
> + wdt->heartbeat -= 4;
That means heartbeat can be 0, correct (if min_heartbeat == 1) ?
Will that work ?
> +
> + if ((tmp & AT91_WDT_WDFIEN) && wdt->irq) {
> + err = request_irq(wdt->irq, wdt_interrupt,
> + IRQF_SHARED | IRQF_IRQPOLL,
> + pdev->name, wdt);
> + if (err)
> + return err;
> + }
> +
> + if ((tmp & wdt->mr_mask) != (wdt->mr & wdt->mr_mask))
> + dev_warn(wdt->wdd.parent,
> + "watchdog already configured differently (mr = %x expecting %x)\n",
> + tmp & wdt->mr_mask, wdt->mr & wdt->mr_mask);
> +
> + setup_timer(&wdt->timer, at91_ping, (unsigned long)wdt);
> + mod_timer(&wdt->timer, jiffies + wdt->heartbeat);
> +
> + /* Try to set timeout from device tree first */
> + if (watchdog_init_timeout(&wdt->wdd, 0, &pdev->dev))
> + watchdog_init_timeout(&wdt->wdd, heartbeat, &pdev->dev);
> + watchdog_set_nowayout(&wdt->wdd, wdt->nowayout);
> + err = watchdog_register_device(&wdt->wdd);
> + if (err)
> + goto out_stop_timer;
> +
> + wdt->next_heartbeat = jiffies + wdt->wdd.timeout * HZ;
>
> return 0;
> +
> +out_stop_timer:
> + del_timer(&wdt->timer);
> + return err;
> }
>
> /* ......................................................................... */
> @@ -167,63 +239,125 @@ static const struct watchdog_info at91_wdt_info = {
>
> static const struct watchdog_ops at91_wdt_ops = {
> .owner = THIS_MODULE,
> - .start = at91_wdt_start,
> + .start = at91_wdt_ping,
> .stop = at91_wdt_stop,
> .ping = at91_wdt_ping,
Notpick, but you don't need both start and ping. If both are the same, providing
start is sufficient. Given this, it might be cleaner to name the function
at91_wdt_start and not provide ping.
> .set_timeout = at91_wdt_set_timeout,
> };
>
> -static struct watchdog_device at91_wdt_dev = {
> - .info = &at91_wdt_info,
> - .ops = &at91_wdt_ops,
> - .timeout = WDT_HEARTBEAT,
> - .min_timeout = 1,
> - .max_timeout = 0xFFFF,
> -};
> +#if defined(CONFIG_OF)
> +static int of_at91wdt_init(struct device_node *np, struct at91wdt *wdt)
> +{
> + u32 min = 0;
> + u32 max = WDT_COUNTER_MAX_SECS;
> + const char *tmp;
> +
> + /* Get the interrupts property */
> + wdt->irq = irq_of_parse_and_map(np, 0);
> + if (!wdt->irq)
> + dev_warn(wdt->wdd.parent, "failed to get IRQ from DT\n");
> +
> + if (!of_property_read_u32_index(np, "atmel,max-heartbeat-sec", 0,
> + &max)) {
> + if (!max || max > WDT_COUNTER_MAX_SECS)
> + max = WDT_COUNTER_MAX_SECS;
> +
> + if (!of_property_read_u32_index(np, "atmel,min-heartbeat-sec",
> + 0, &min)) {
> + if (min >= max)
> + min = max - 1;
> + }
> + }
> +
> + min = secs_to_ticks(min);
> + max = secs_to_ticks(max);
> +
> + wdt->mr_mask = 0x3FFFFFFF;
> + wdt->mr = 0;
> + if (!of_property_read_string(np, "atmel,watchdog-type", &tmp) &&
> + !strcmp(tmp, "software")) {
> + wdt->mr |= AT91_WDT_WDFIEN;
> + wdt->mr_mask &= ~AT91_WDT_WDRPROC;
> + } else
> + wdt->mr |= AT91_WDT_WDRSTEN;
> +
> + if (!of_property_read_string(np, "atmel,reset-type", &tmp) &&
> + !strcmp(tmp, "proc"))
> + wdt->mr |= AT91_WDT_WDRPROC;
> +
> + if (of_property_read_bool(np, "atmel,disable")) {
> + wdt->mr |= AT91_WDT_WDDIS;
> + wdt->mr_mask &= AT91_WDT_WDDIS;
> + }
> +
> + if (of_property_read_bool(np, "atmel,idle-halt"))
> + wdt->mr |= AT91_WDT_WDIDLEHLT;
> +
> + if (of_property_read_bool(np, "atmel,dbg-halt"))
> + wdt->mr |= AT91_WDT_WDDBGHLT;
> +
> + wdt->mr |= max | ((max - min) << 16);
> +
> + return 0;
> +}
> +#else
> +static inline int of_at91wdt_init(struct device_node *np, struct at91wdt *wdt)
> +{
> + return 0;
> +}
> +#endif
>
> static int __init at91wdt_probe(struct platform_device *pdev)
> {
> struct resource *r;
> - int res;
> + int err;
> + struct at91wdt *wdt;
>
> - r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> - if (!r)
> - return -ENODEV;
> - at91wdt_private.base = ioremap(r->start, resource_size(r));
> - if (!at91wdt_private.base) {
> - dev_err(&pdev->dev, "failed to map registers, aborting.\n");
> + wdt = devm_kzalloc(&pdev->dev, sizeof(*wdt), GFP_KERNEL);
> + if (!wdt)
> return -ENOMEM;
> - }
>
> - at91_wdt_dev.parent = &pdev->dev;
> - watchdog_init_timeout(&at91_wdt_dev, heartbeat, &pdev->dev);
> - watchdog_set_nowayout(&at91_wdt_dev, nowayout);
> + wdt->mr = (WDT_HW_TIMEOUT * 256) | AT91_WDT_WDRSTEN | AT91_WDT_WDD |
> + AT91_WDT_WDDBGHLT | AT91_WDT_WDIDLEHLT;
> + wdt->mr_mask = 0x3FFFFFFF;
> + wdt->nowayout = nowayout;
> + wdt->wdd.parent = &pdev->dev;
> + wdt->wdd.info = &at91_wdt_info;
> + wdt->wdd.ops = &at91_wdt_ops;
> + wdt->wdd.timeout = WDT_HEARTBEAT;
> + wdt->wdd.min_timeout = 1;
> + wdt->wdd.max_timeout = 0xFFFF;
>
> - /* Set watchdog */
> - res = at91_wdt_settimeout(ms_to_ticks(WDT_HW_TIMEOUT * 1000));
> - if (res)
> - return res;
> + r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> + wdt->base = devm_ioremap_resource(&pdev->dev, r);
> + if (IS_ERR(wdt->base))
> + return PTR_ERR(wdt->base);
> +
> + if (pdev->dev.of_node) {
> + err = of_at91wdt_init(pdev->dev.of_node, wdt);
> + if (err)
> + return err;
> + }
>
> - res = watchdog_register_device(&at91_wdt_dev);
> - if (res)
> - return res;
> + err = at91_wdt_init(pdev, wdt);
> + if (err)
> + return err;
>
> - at91wdt_private.next_heartbeat = jiffies + at91_wdt_dev.timeout * HZ;
> - setup_timer(&at91wdt_private.timer, at91_ping, 0);
> - mod_timer(&at91wdt_private.timer, jiffies + WDT_TIMEOUT);
> + platform_set_drvdata(pdev, wdt);
>
> pr_info("enabled (heartbeat=%d sec, nowayout=%d)\n",
> - at91_wdt_dev.timeout, nowayout);
> + wdt->wdd.timeout, wdt->nowayout);
>
> return 0;
> }
>
> static int __exit at91wdt_remove(struct platform_device *pdev)
> {
> - watchdog_unregister_device(&at91_wdt_dev);
> + struct at91wdt *wdt = platform_get_drvdata(pdev);
> + watchdog_unregister_device(&wdt->wdd);
>
> pr_warn("I quit now, hardware will probably reboot!\n");
> - del_timer(&at91wdt_private.timer);
> + del_timer(&wdt->timer);
>
> return 0;
> }
> --
> 1.7.9.5
>
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