[PATCH v1] iTCO_wdt: ignore NMI_NOW bit on register comparison

[Oleksandr Ocheretnyi]

Commit da23b6faa8bf ("watchdog: iTCO: Add support for Cannon Lake
PCH iTCO") does not ignore NMI_NOW bit on write operation to TCO1_CNT
register what causes unexpected NMIs due to NMI_NOW bit inversion
during regular crashkernel's workflow with following logs:

iTCO_vendor_support: vendor-support=0
iTCO_wdt iTCO_wdt: unable to reset NO_REBOOT flag, device
                                            disabled by hardware/BIOS

This change clears NMI_NOW bit in the TCO1_CNT register to have no
effect on NMI_NOW bit inversion what can cause NMI immediately.

Fixes: da23b6faa8bf ("watchdog: iTCO: Add support for Cannon Lake PCH iTCO")
Signed-off-by: Oleksandr Ocheretnyi <oocheret@xxxxxxxxx>
---
 drivers/watchdog/iTCO_wdt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/watchdog/iTCO_wdt.c b/drivers/watchdog/iTCO_wdt.c
index 264857d314da..679c115ef7d3 100644
--- a/drivers/watchdog/iTCO_wdt.c
+++ b/drivers/watchdog/iTCO_wdt.c
@@ -224,7 +224,7 @@ static int update_no_reboot_bit_cnt(void *priv, bool set)
 		val |= BIT(0);
 	else
 		val &= ~BIT(0);
-	outw(val, TCO1_CNT(p));
+	outw(val & ~BIT(8), TCO1_CNT(p));
 	newval = inw(TCO1_CNT(p));
 
 	/* make sure the update is successful */
-- 
2.39.3