Re: [PATCH (v2) 7/10] watchdog: bcm63xx_wdt: Add get_timeleft function

Guenter Roeck
2015-11-25T02:51:00Z

On 11/24/2015 02:15 PM, Simon Arlott wrote:
> Return the remaining time from the hardware control register.
>
> Warn when the device is registered if the hardware watchdog is currently
> running and report the remaining time left.

This is really two logical changes, isn't it ?

Nice trick to figure out if the watchdog is running.

What is the impact ? Will this result in interrupts ?
If so, would it make sense to _not_ reset the system after a timeout
in this case, but to keep pinging the watchdog while the watchdog device
is not open ?

Thanks,
Guenter

>
> Signed-off-by: Simon Arlott <simon-A6De1vDTPLDsq35pWSNszA@public.gmane.org>
> ---
> Changed "if (timeleft > 0)" to "if (hw->running)" when checking if a
> warning should be printed, in case the time left is truncated down to
> 0 seconds.
>
> drivers/watchdog/bcm63xx_wdt.c | 37 +++++++++++++++++++++++++++++++++++++
> 1 file changed, 37 insertions(+)
>
> diff --git a/drivers/watchdog/bcm63xx_wdt.c b/drivers/watchdog/bcm63xx_wdt.c
> index 3c7667a..9d099e0 100644
> --- a/drivers/watchdog/bcm63xx_wdt.c
> +++ b/drivers/watchdog/bcm63xx_wdt.c
> @@ -14,6 +14,7 @@
> #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
>
> #include <linux/clk.h>
> +#include <linux/delay.h>
> #include <linux/errno.h>
> #include <linux/io.h>
> #include <linux/kernel.h>
> @@ -75,6 +76,19 @@ static int bcm63xx_wdt_stop(struct watchdog_device *wdd)
> return 0;
> }
>
> +static unsigned int bcm63xx_wdt_get_timeleft(struct watchdog_device *wdd)
> +{
> + struct bcm63xx_wdt_hw *hw = watchdog_get_drvdata(wdd);
> + unsigned long flags;
> + u32 val;
> +
> + raw_spin_lock_irqsave(&hw->lock, flags);
> + val = __raw_readl(hw->regs + WDT_CTL_REG);
> + val /= hw->clock_hz;
> + raw_spin_unlock_irqrestore(&hw->lock, flags);
> + return val;
> +}
> +
> static int bcm63xx_wdt_set_timeout(struct watchdog_device *wdd,
> unsigned int timeout)
> {
> @@ -130,6 +144,7 @@ static struct watchdog_ops bcm63xx_wdt_ops = {
> .owner = THIS_MODULE,
> .start = bcm63xx_wdt_start,
> .stop = bcm63xx_wdt_stop,
> + .get_timeleft = bcm63xx_wdt_get_timeleft,
> .set_timeout = bcm63xx_wdt_set_timeout,
> };
>
> @@ -144,6 +159,8 @@ static int bcm63xx_wdt_probe(struct platform_device *pdev)
> struct bcm63xx_wdt_hw *hw;
> struct watchdog_device *wdd;
> struct resource *r;
> + u32 timeleft1, timeleft2;
> + unsigned int timeleft;
> int ret;
>
> hw = devm_kzalloc(&pdev->dev, sizeof(*hw), GFP_KERNEL);
> @@ -197,6 +214,23 @@ static int bcm63xx_wdt_probe(struct platform_device *pdev)
> watchdog_init_timeout(wdd, 0, &pdev->dev);
> watchdog_set_nowayout(wdd, nowayout);
>
> + /* Compare two reads of the time left value, 2 clock ticks apart */
> + rmb();
> + timeleft1 = __raw_readl(hw->regs + WDT_CTL_REG);
> + udelay(DIV_ROUND_UP(1000000, hw->clock_hz / 2));
> + /* Ensure the register is read twice */
> + rmb();
> + timeleft2 = __raw_readl(hw->regs + WDT_CTL_REG);
> +
> + /* If the time left is changing, the watchdog is running */
> + if (timeleft1 != timeleft2) {
> + hw->running = true;
> + timeleft = bcm63xx_wdt_get_timeleft(wdd);
> + } else {
> + hw->running = false;
> + timeleft = 0;
> + }
> +
> ret = bcm63xx_timer_register(TIMER_WDT_ID, bcm63xx_wdt_isr, wdd);
> if (ret < 0) {
> dev_err(&pdev->dev, "failed to register wdt timer isr\n");
> @@ -214,6 +248,8 @@ static int bcm63xx_wdt_probe(struct platform_device *pdev)
> dev_name(wdd->dev), hw->regs,
> wdd->timeout, wdd->max_timeout);
>
> + if (hw->running)
> + dev_alert(wdd->dev, "running, reboot in %us\n", timeleft);
> return 0;
>
> unregister_timer:
> @@ -255,6 +291,7 @@ module_platform_driver(bcm63xx_wdt_driver);
>
> MODULE_AUTHOR("Miguel Gaio <miguel.gaio-HH44TBFINEIAvxtiuMwx3w@public.gmane.org>");
> MODULE_AUTHOR("Florian Fainelli <florian-p3rKhJxN3npAfugRpC6u6w@public.gmane.org>");
> +MODULE_AUTHOR("Simon Arlott");
> MODULE_DESCRIPTION("Driver for the Broadcom BCM63xx SoC watchdog");
> MODULE_LICENSE("GPL");
> MODULE_ALIAS("platform:bcm63xx-wdt");