| Message ID | 2d539bc944f3e8fc70f39728b0f61fd171b2e5bf.1411513109.git.joshc@codeaurora.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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@codeaurora.org> > --- > 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 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-watchdog" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html
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 + */ + 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); + 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;
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@codeaurora.org> --- drivers/watchdog/qcom-wdt.c | 28 ++++++++++++++++++++++++++++ 1 file changed, 28 insertions(+)