From: Jan Kiszka <jan.kiszka@siemens.com>
To: Guenter Roeck <linux@roeck-us.net>
Cc: Wim Van Sebroeck <wim@linux-watchdog.org>,
linux-watchdog@vger.kernel.org,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Paolo Bonzini <pbonzini@redhat.com>,
Christian Storm <christian.storm@siemens.com>,
Andy Shevchenko <andy.shevchenko@gmail.com>
Subject: Re: [PATCH v2] watchdog: iTCO_wdt: Account for rebooting on second timeout
Date: Mon, 31 May 2021 10:27:53 +0200 [thread overview]
Message-ID: <5bf45bf8-0cd6-a131-fe11-1651ed60e8cc@siemens.com> (raw)
In-Reply-To: <20210530131947.GB2483596@roeck-us.net>
On 30.05.21 15:19, Guenter Roeck wrote:
> 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 ?
Yes, this is intended. You find the reference to "reboots on second
timeout" even in latest EHL datasheets (v6).
Jan
>
> 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
--
Siemens AG, T RDA IOT
Corporate Competence Center Embedded Linux
next prev parent reply other threads:[~2021-05-31 8:31 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-30 11:24 [PATCH v2] watchdog: iTCO_wdt: Account for rebooting on second timeout Jan Kiszka
2021-05-30 13:19 ` Guenter Roeck
2021-05-31 8:27 ` Jan Kiszka [this message]
2021-05-31 9:18 ` Jan Kiszka
2021-06-02 11:24 ` Guenter Roeck
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