Hello, We had reports of Aspeed BMC systems entering a reboot loop, each time attempting and failing to probe some PMBus devices. For whatever reason the PMBus devices weren't appearing on the I2C bus, and several factors came into play: 1. i2c-aspeed's transfer timeout is set to 5 seconds 2. The kernel's pmbus core now tests for the presence of the status word, then the status byte. Not all devices support the status word, therefore on error we fall back to probing the status byte. This leads to back-to-back uninterruptible transfers, totalling 10 seconds of delay if the device is not present before propagating a probe error back up the call chain 3. The BMC watchdogs are enabled by u-boot to catch a kernel hang 4. The hardware's default watchdog counter value equates to a 22 second period 5. The watchdog driver is probed after the I2C subsystem iterates all the described devices. Thus as it stands nearly 50% of the watchdog period can be spent dealing with one missing PMBus device. Arguably the I2C timeout value is too large, but as the watchdog driver is not probed until after the I2C busses are iterated, the work to ping the watchdog cannot even be scheduled to take place between transfers. Patch 4 shifts aspeed_wdt to arch_initcall so the watchdog can be pinged as needed. Patch 1 fixes an oversight that lead to the watchdogs being disabled until userspace opened the chardev. The remaining two patches are minor fixes to the Kconfig. Please review! Cheers, Andrew Andrew Jeffery (4): watchdog: aspeed: Retain watchdog enabled state watchdog: aspeed: Fix 'Apseed' typo in Kconfig watchdog: aspeed: Remove specific reference to AST2400 in Kconfig watchdog: aspeed: Move init to arch_initcall drivers/watchdog/Kconfig | 8 +++----- drivers/watchdog/aspeed_wdt.c | 16 +++++++++++----- 2 files changed, 14 insertions(+), 10 deletions(-) -- 2.11.0 -- To unsubscribe from this list: send the line "unsubscribe linux-watchdog" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
