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

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Message-Id: <20240826075303.3964392-1-oocheret@cisco.com>
Date: Mon, 26 Aug 2024 00:53:01 -0700
From: Oleksandr Ocheretnyi <oocheret@...co.com>
To: Wim Van Sebroeck <wim@...ux-watchdog.org>,
        Guenter Roeck <linux@...ck-us.net>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Jean Delvare <jdelvare@...e.de>, Wolfram Sang <wsa@...nel.org>,
        linux-watchdog@...r.kernel.org, linux-kernel@...r.kernel.org
Cc: xe-linux-external@...co.com, Oleksandr Ocheretnyi <oocheret@...co.com>
Subject: [PATCH v1] iTCO_wdt: ignore NMI_NOW bit on register comparison

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@...co.com>
---
 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