tree faa95187dcbc3edc36fdcad588b0cbd8b0798fee
parent 5e192ddf4be40568e2289d2fd0e0033ba601cbad
author Boyan Karatotev <boyan.karatotev@arm.com> 1744277087 +0100
committer Boyan Karatotev <boyan.karatotev@arm.com> 1750923794 +0100

fix(psci): do not modify higher levels for standby in OSI mode

The OSI mode for the CPU standby fast path updates the requested power
states incorrectly. psci_update_req_local_pwr_states() will not bother
saving level 0. It will also clamp the level it accesses to the
end_pwrlvl argument. Well, in the fast path, this argument is always 0
(as a condition of entering the fast path). The result is that it reads
the level 0 power state (retention) and writes it to the level 1 power
state, even though by definition, the fast path will not update higher
power levels.

The fix is to pass PLAT_MAX_PWR_LVL instead of target_pwrlvl to
psci_update_req_local_pwr_states(). However, doing that makes it
apparent that this call will not change anything and therefore there is
nothing to save - the level 0 power state is written by
psci_set_cpu_local_state(). So the save + restore are redundant. Remove
them to save on a bunch of work.

Another thing that is not considered is locking. No locks are held in
the fast path, so these updates are not safe.

Change-Id: Icc785df87b294b938b59705116369abd80ccf4da
Signed-off-by: Boyan Karatotev <boyan.karatotev@arm.com>