6.6-stable review patch. If anyone has any objections, please let me know.
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From: Oleksandr Ocheretnyi oocheret@cisco.com
[ Upstream commit daa814d784ac034c62ab3fb0ef83daeafef527e2 ]
Commit da23b6faa8bf ("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: da23b6faa8bf ("watchdog: iTCO: Add support for Cannon Lake PCH iTCO") Signed-off-by: Oleksandr Ocheretnyi oocheret@cisco.com Reviewed-by: Guenter Roeck linux@roeck-us.net Reviewed-by: Mika Westerberg mika.westerberg@linux.intel.com Link: https://lore.kernel.org/r/20240913191403.2560805-1-oocheret@cisco.com Signed-off-by: Guenter Roeck linux@roeck-us.net Signed-off-by: Wim Van Sebroeck wim@linux-watchdog.org Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/watchdog/iTCO_wdt.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-)
diff --git a/drivers/watchdog/iTCO_wdt.c b/drivers/watchdog/iTCO_wdt.c index 264857d314da8..dd297dcd524c9 100644 --- a/drivers/watchdog/iTCO_wdt.c +++ b/drivers/watchdog/iTCO_wdt.c @@ -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;