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Commit f72fa00f authored by Boris Brezillon's avatar Boris Brezillon Committed by Wim Van Sebroeck
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watchdog: at91sam9_wdt: increase security margin on watchdog counter reset 



Try to reset the watchdog counter 4 or 2 times more often than actually
requested, to avoid spurious watchdog reset.
If this is not possible because of the min_heartbeat value, reset it at
the min_heartbeat period.

Signed-off-by: default avatarBoris BREZILLON <b.brezillon@overkiz.com>
Reviewed-by: default avatarGuenter Roeck <linux@roeck-us.net>
Signed-off-by: default avatarWim Van Sebroeck <wim@iguana.be>
parent a04c3f01

drivers/watchdog/at91sam9_wdt.c

+16 −9
Original line number Diff line number Diff line
@@ -158,6 +158,7 @@ static int at91_wdt_init(struct platform_device *pdev, struct at91wdt *wdt) 
	int err;

	u32 mask = wdt->mr_mask;

	unsigned long min_heartbeat = 1;

	unsigned long max_heartbeat;

	struct device *dev = &pdev->dev;



	tmp = wdt_read(wdt, AT91_WDT_MR);
@@ -181,23 +182,29 @@ static int at91_wdt_init(struct platform_device *pdev, struct at91wdt *wdt) 
	if (delta < value)

		min_heartbeat = ticks_to_hz_roundup(value - delta);



	wdt->heartbeat = ticks_to_hz_rounddown(value);

	if (!wdt->heartbeat) {

	max_heartbeat = ticks_to_hz_rounddown(value);

	if (!max_heartbeat) {

		dev_err(dev,

			"heartbeat is too small for the system to handle it correctly\n");

		return -EINVAL;

	}



	if (wdt->heartbeat < min_heartbeat + 4) {

	/*

	 * Try to reset the watchdog counter 4 or 2 times more often than

	 * actually requested, to avoid spurious watchdog reset.

	 * If this is not possible because of the min_heartbeat value, reset

	 * it at the min_heartbeat period.

	 */

	if ((max_heartbeat / 4) >= min_heartbeat)

		wdt->heartbeat = max_heartbeat / 4;

	else if ((max_heartbeat / 2) >= min_heartbeat)

		wdt->heartbeat = max_heartbeat / 2;

	else

		wdt->heartbeat = min_heartbeat;



	if (max_heartbeat < min_heartbeat + 4)

		dev_warn(dev,

			 "min heartbeat and max heartbeat might be too close for the system to handle it correctly\n");

		if (wdt->heartbeat < 4)

			dev_warn(dev,

				 "heartbeat might be too small for the system to handle it correctly\n");

	} else {

		wdt->heartbeat -= 4;

	}



	if ((tmp & AT91_WDT_WDFIEN) && wdt->irq) {

		err = request_irq(wdt->irq, wdt_interrupt,