| Message ID | 20240913191403.2560805-1-oocheret@cisco.com |
|---|---|
| State | New |
| Headers | show |
| Series | [v3] iTCO_wdt: mask NMI_NOW bit for update_no_reboot_bit() call | expand |
On 9/13/24 12:14, Oleksandr Ocheretnyi wrote: > 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> > --- > V2 -> V3: Removed not necessary variable 'mask', updated multi-line comments > V1 -> V2: Provided comments and macro define with bit description > > 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 264857d314da..dd297dcd524c 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;
Hello Mika, > I suggest adding some #define for the magical number 8 so that it is > easier for anyone looking at this driver to figure out what it is doing. Are the changes with #define NMI_NOW bit fine for you? Best regards, Oleksandr
On Mon, Oct 07, 2024 at 08:57:02AM -0700, Oleksandr Ocheretnyi wrote: > Hello Mika, > > > I suggest adding some #define for the magical number 8 so that it is > > easier for anyone looking at this driver to figure out what it is doing. > > Are the changes with #define NMI_NOW bit fine for you? Sure, Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
diff --git a/drivers/watchdog/iTCO_wdt.c b/drivers/watchdog/iTCO_wdt.c index 264857d314da..dd297dcd524c 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;
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> --- V2 -> V3: Removed not necessary variable 'mask', updated multi-line comments V1 -> V2: Provided comments and macro define with bit description drivers/watchdog/iTCO_wdt.c | 21 +++++++++++++++++++-- 1 file changed, 19 insertions(+), 2 deletions(-)