Commit daa814d7 authored by Oleksandr Ocheretnyi's avatar Oleksandr Ocheretnyi Committed by Wim Van Sebroeck
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iTCO_wdt: mask NMI_NOW bit for update_no_reboot_bit() call 



Commit da23b6fa ("watchdog: iTCO: Add support for Cannon Lake
PCH iTCO") does not mask NMI_NOW bit during TCO1_CNT register's
value comparison for update_no_reboot_bit() call causing following
failure:

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

and this can lead to unexpected NMIs later during regular
crashkernel's workflow because of watchdog probe call failures.

This change masks NMI_NOW bit for TCO1_CNT register values to
avoid unexpected NMI_NOW bit inversions.

Fixes: da23b6fa ("watchdog: iTCO: Add support for Cannon Lake PCH iTCO")
Signed-off-by: default avatarOleksandr Ocheretnyi <oocheret@cisco.com>
Reviewed-by: default avatarGuenter Roeck <linux@roeck-us.net>
Reviewed-by: default avatarMika Westerberg <mika.westerberg@linux.intel.com>
Link: https://lore.kernel.org/r/20240913191403.2560805-1-oocheret@cisco.com


Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
Signed-off-by: default avatarWim Van Sebroeck <wim@linux-watchdog.org>
parent 4497ee91

drivers/watchdog/iTCO_wdt.c

+19 −2
Original line number Diff line number Diff line
@@ -82,6 +82,13 @@ 
#define TCO2_CNT(p)	(TCOBASE(p) + 0x0a) /* TCO2 Control Register	*/

#define TCOv2_TMR(p)	(TCOBASE(p) + 0x12) /* TCOv2 Timer Initial Value*/



/*

 * NMI_NOW is bit 8 of TCO1_CNT register

 * Read/Write

 * This bit is implemented as RW but has no effect on HW.

 */

#define NMI_NOW		BIT(8)



/* internal variables */

struct iTCO_wdt_private {

	struct watchdog_device wddev;
@@ -219,13 +226,23 @@ static int update_no_reboot_bit_cnt(void *priv, bool set) 
	struct iTCO_wdt_private *p = priv;

	u16 val, newval;



	val = inw(TCO1_CNT(p));

	/*

	 * writing back 1b1 to NMI_NOW of TCO1_CNT register

	 * causes NMI_NOW bit inversion what consequently does

	 * not allow to perform the register's value comparison

	 * properly.

	 *

	 * NMI_NOW bit masking for TCO1_CNT register values

	 * helps to avoid possible NMI_NOW bit inversions on

	 * following write operation.

	 */

	val = inw(TCO1_CNT(p)) & ~NMI_NOW;

	if (set)

		val |= BIT(0);

	else

		val &= ~BIT(0);

	outw(val, TCO1_CNT(p));

	newval = inw(TCO1_CNT(p));

	newval = inw(TCO1_CNT(p)) & ~NMI_NOW;



	/* make sure the update is successful */

	return val != newval ? -EIO : 0;