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    SubjectRe: [PATCH v2] watchdog: iTCO_wdt: Account for rebooting on second timeout
    On Sun, May 30, 2021 at 01:24:23PM +0200, Jan Kiszka wrote:
    > From: Jan Kiszka <jan.kiszka@siemens.com>
    >
    > This was already attempted to fix via 1fccb73011ea: If the BIOS did not
    > enable TCO SMIs, the timer definitely needs to trigger twice in order to
    > cause a reboot. If TCO SMIs are on, as well as SMIs in general, we can
    > continue to assume that the BIOS will perform a reboot on the first
    > timeout.
    >
    > QEMU with its ICH9 and related BIOS falls into the former category,
    > currently taking twice the configured timeout in order to reboot the
    > machine. For iTCO version that fall under turn_SMI_watchdog_clear_off,
    > this is also true and was currently only addressed for v1, irrespective
    > of the turn_SMI_watchdog_clear_off value.
    >
    > Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
    > ---
    >
    > Changes in v2:
    > - consider GBL_SMI_EN as well
    >
    > drivers/watchdog/iTCO_wdt.c | 12 +++++++++---
    > 1 file changed, 9 insertions(+), 3 deletions(-)
    >
    > diff --git a/drivers/watchdog/iTCO_wdt.c b/drivers/watchdog/iTCO_wdt.c
    > index bf31d7b67a69..3f1324871cfd 100644
    > --- a/drivers/watchdog/iTCO_wdt.c
    > +++ b/drivers/watchdog/iTCO_wdt.c
    > @@ -71,6 +71,8 @@
    > #define TCOBASE(p) ((p)->tco_res->start)
    > /* SMI Control and Enable Register */
    > #define SMI_EN(p) ((p)->smi_res->start)
    > +#define TCO_EN (1 << 13)
    > +#define GBL_SMI_EN (1 << 0)
    >
    > #define TCO_RLD(p) (TCOBASE(p) + 0x00) /* TCO Timer Reload/Curr. Value */
    > #define TCOv1_TMR(p) (TCOBASE(p) + 0x01) /* TCOv1 Timer Initial Value*/
    > @@ -355,8 +357,12 @@ static int iTCO_wdt_set_timeout(struct watchdog_device *wd_dev, unsigned int t)
    >
    > tmrval = seconds_to_ticks(p, t);
    >
    > - /* For TCO v1 the timer counts down twice before rebooting */
    > - if (p->iTCO_version == 1)
    > + /*
    > + * If TCO SMIs are off, the timer counts down twice before rebooting.
    > + * Otherwise, the BIOS generally reboots when the SMI triggers.
    > + */
    > + if (p->smi_res &&
    > + (SMI_EN(p) & (TCO_EN | GBL_SMI_EN)) != (TCO_EN | GBL_SMI_EN))
    > tmrval /= 2;

    This expands the scope of this adjustment to all versions, while at the same
    time making it conditional for v1. Is this correct ? What for systems with v1
    TCO where the above conditions are not met ?

    Guenter

    >
    > /* from the specs: */
    > @@ -521,7 +527,7 @@ static int iTCO_wdt_probe(struct platform_device *pdev)
    > * Disables TCO logic generating an SMI#
    > */
    > val32 = inl(SMI_EN(p));
    > - val32 &= 0xffffdfff; /* Turn off SMI clearing watchdog */
    > + val32 &= ~TCO_EN; /* Turn off SMI clearing watchdog */
    > outl(val32, SMI_EN(p));
    > }
    >
    > --
    > 2.26.2

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