Re: [PATCH stable v4.4] powerpc/pseries: Do not initiate shutdown when system is running on UPS

[Sasha Levin <sashal@kernel.org>]

On Thu, Aug 27, 2020 at 01:13:07PM +0530, Vasant Hegde wrote:
>commit 90a9b102eddf6a3f987d15f4454e26a2532c1c98 upstream.
>
>As per PAPR we have to look for both EPOW sensor value and event
>modifier to identify the type of event and take appropriate action.
>
>In LoPAPR v1.1 section 10.2.2 includes table 136 "EPOW Action Codes":
>
>  SYSTEM_SHUTDOWN 3
>
>  The system must be shut down. An EPOW-aware OS logs the EPOW error
>  log information, then schedules the system to be shut down to begin
>  after an OS defined delay internal (default is 10 minutes.)
>
>Then in section 10.3.2.2.8 there is table 146 "Platform Event Log
>Format, Version 6, EPOW Section", which includes the "EPOW Event
>Modifier":
>
>  For EPOW sensor value = 3
>  0x01 = Normal system shutdown with no additional delay
>  0x02 = Loss of utility power, system is running on UPS/Battery
>  0x03 = Loss of system critical functions, system should be shutdown
>  0x04 = Ambient temperature too high
>  All other values = reserved
>
>We have a user space tool (rtas_errd) on LPAR to monitor for
>EPOW_SHUTDOWN_ON_UPS. Once it gets an event it initiates shutdown
>after predefined time. It also starts monitoring for any new EPOW
>events. If it receives "Power restored" event before predefined time
>it will cancel the shutdown. Otherwise after predefined time it will
>shutdown the system.
>
>Commit 79872e35469b ("powerpc/pseries: All events of
>EPOW_SYSTEM_SHUTDOWN must initiate shutdown") changed our handling of
>the "on UPS/Battery" case, to immediately shutdown the system. This
>breaks existing setups that rely on the userspace tool to delay
>shutdown and let the system run on the UPS.
>
>Fixes: 79872e35469b ("powerpc/pseries: All events of EPOW_SYSTEM_SHUTDOWN must initiate shutdown")
>Cc: stable@vger.kernel.org # v4.0+
>Signed-off-by: Vasant Hegde <hegdevasant@linux.vnet.ibm.com>
>[mpe: Massage change log and add PAPR references]
>Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
>Link: https://lore.kernel.org/r/20200820061844.306460-1-hegdevasant@linux.vnet.ibm.com
>Signed-off-by: Vasant Hegde <hegdevasant@linux.vnet.ibm.com>
>---
>Hi,
>  Please apply this patch to linux-stable-v4.4 branch. Its already applied to
>  other required stable branches.

Queued up, thanks!

-- 
Thanks,
Sasha