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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: Boris BREZILLON <b.brezillon@overkiz.com>
Reviewed-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
This commit is contained in:
Boris BREZILLON 2013-11-03 18:52:44 +01:00 committed by Wim Van Sebroeck
parent a04c3f01d3
commit f72fa00f8a
1 changed files with 16 additions and 9 deletions
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25
drivers/watchdog/at91sam9_wdt.c
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@ -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,