[PATCH v2 3/3] watchdog: qcom: register a restart notifier
From: linux@roeck-us.net (Guenter Roeck)
Date: 2014-09-24 17:05:29
Also in:
linux-arm-msm, linux-watchdog, lkml
On Tue, Sep 23, 2014 at 06:04:38PM -0500, Josh Cartwright wrote:
quoted hunk ↗ jump to hunk
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 <redacted> --- 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
quoted hunk ↗ jump to hunk
+ 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 at vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html