From: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
To: Primoz Fiser <primoz.fiser@norik.com>,
"linux-watchdog@vger.kernel.org" <linux-watchdog@vger.kernel.org>,
Guenter Roeck <linux@roeck-us.net>,
Wim Van Sebroeck <wim@linux-watchdog.org>,
Support Opensource <Support.Opensource@diasemi.com>
Cc: Tero Kristo <t-kristo@ti.com>,
Stefan Riedmueller <s.riedmueller@phytec.de>,
Wolfram Sang <wsa+renesas@sang-engineering.com>
Subject: RE: [PATCH v2] watchdog: da9062: da9063: prevent pings ahead of machine reset
Date: Thu, 8 Jul 2021 14:15:17 +0000 [thread overview]
Message-ID: <DB9PR10MB4652FCD8EB538492E66BD52880199@DB9PR10MB4652.EURPRD10.PROD.OUTLOOK.COM> (raw)
In-Reply-To: <20210708082128.2832904-1-primoz.fiser@norik.com>
On 08 July 2021 09:21, Primoz Fiser wrote:
> Proper machine resets via da9062/da9063 PMICs are very tricky as they
> require special i2c atomic transfers when interrupts are not available
> anymore. This is also a reason why both PMIC's restart handlers do not
> use regmap but instead opt for i2c_smbus_write_byte_data() which does
> i2c transfer in atomic manner. Under the hood, this function tries to
> obtain i2c bus lock with call to i2c_adapter_trylock_bus() which will
> return -EAGAIN (-11) if lock is not available.
>
> Since commit 982bb70517aef ("watchdog: reset last_hw_keepalive time at
> start") occasional restart handler failures with "Failed to shutdown
> (err = -11)" error messages were observed, indicating that some
> process is holding the i2c bus lock. Investigation into the matter
> uncovered that sometimes during reboot sequence watchdog ping is issued
> late into poweroff/reboot phase which did not happen before mentioned
> commit (usually the watchdog ping happened immediately as commit message
> suggests). As of now, when watchdog ping usually happens late into
> poweroff/reboot stage when interrupts are not available anymore, i2c bus
> lock cannot be released anymore and pending restart handler in turn
> fails.
>
> Thus, to prevent such late watchdog pings from happening ahead of
> pending machine restart and consequently locking up the i2c bus, check
> for system_state in watchdog ping handler and consequently do not send
> pings anymore in case system_state > SYSTEM_RUNNING.
>
> Signed-off-by: Primoz Fiser <primoz.fiser@norik.com>
Reviewed-by: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
prev parent reply other threads:[~2021-07-08 14:15 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-06 11:21 [PATCH] watchdog: da9062: da9063: prevent watchdog pings ahead of reboot Primoz Fiser
2021-07-06 13:28 ` Guenter Roeck
2021-07-07 4:39 ` Primoz Fiser
2021-07-08 8:21 ` [PATCH v2] watchdog: da9062: da9063: prevent pings ahead of machine reset Primoz Fiser
2021-07-08 14:00 ` Guenter Roeck
2021-07-08 14:15 ` Adam Thomson [this message]
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