On Tue, Sep 23, 2014 at 06:04:38PM -0500, Josh Cartwright wrote:
> The WDT's BITE_TIME warm-reset behavior can be leveraged as a last
> resort mechanism for triggering chip reset. Usually, other restart
> methods (such as PS_HOLD) are preferrable for issuing a more complete
> reset of the chip. As such, keep the priority of the watchdog notifier
> low.
>
> Signed-off-by: Josh Cartwright <joshc@xxxxxxxxxxxxxx>
> ---
> drivers/watchdog/qcom-wdt.c | 28 ++++++++++++++++++++++++++++
> 1 file changed, 28 insertions(+)
>
> diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
> index d5e46e2..eba92ef 100644
> --- a/drivers/watchdog/qcom-wdt.c
> +++ b/drivers/watchdog/qcom-wdt.c
> @@ -16,6 +16,7 @@
> #include <linux/module.h>
> #include <linux/of.h>
> #include <linux/platform_device.h>
> +#include <linux/reboot.h>
> #include <linux/watchdog.h>
>
> #define WDT_RST 0x0
> @@ -25,6 +26,7 @@
> struct qcom_wdt {
> struct watchdog_device wdd;
> struct clk *clk;
> + struct notifier_block restart_nb;
> void __iomem *base;
> };
>
> @@ -86,6 +88,23 @@ static const struct watchdog_info qcom_wdt_info = {
> .identity = KBUILD_MODNAME,
> };
>
> +static int qcom_wdt_restart(struct notifier_block *nb, unsigned long action,
> + void *data)
> +{
> + struct qcom_wdt *wdt = container_of(nb, struct qcom_wdt, restart_nb);
> +
> + /*
> + * Trigger watchdog bite:
> + * Setup BITE_TIME to be very low, and enable WDT.
> + * 0x31F3 => 390ms @ 32kHz, also value at reset
What happens if you set it to a lower value ? If you set it to, say,
0x100, would the timeout be ~8ms ? Wouldn't that make more sense ?
Or at least something like 0x800, which should make it around 64 ms,
or 0x400 for 32 ms.
[ In other words, I don't really see the point for a 390 ms wait here ]
> + */
> + writel(0, wdt->base + WDT_EN);
> + writel(1, wdt->base + WDT_RST);
> + writel(0x31F3, wdt->base + WDT_BITE_TIME);
> + writel(1, wdt->base + WDT_EN);
You should have some mdelay() here, larger than the expected timeout.
Thanks,
Guenter
> + return NOTIFY_DONE;
> +}
> +
> static int qcom_wdt_probe(struct platform_device *pdev)
> {
> struct qcom_wdt *wdt;
> @@ -141,6 +160,14 @@ static int qcom_wdt_probe(struct platform_device *pdev)
> return ret;
> }
>
> + /*
> + * WDT restart notifier has priority 0 (use as a last resort)
> + */
> + wdt->restart_nb.notifier_call = qcom_wdt_restart;
> + ret = register_restart_handler(&wdt->restart_nb);
> + if (ret)
> + dev_err(&pdev->dev, "failed to setup restart handler\n");
> +
> platform_set_drvdata(pdev, wdt);
> return 0;
> }
> @@ -149,6 +176,7 @@ static int qcom_wdt_remove(struct platform_device *pdev)
> {
> struct qcom_wdt *wdt = platform_get_drvdata(pdev);
>
> + unregister_restart_handler(&wdt->restart_nb);
> watchdog_unregister_device(&wdt->wdd);
> clk_disable_unprepare(wdt->clk);
> return 0;
> --
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
> hosted by The Linux Foundation
>
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