Commit 1e25d805 authored by Rafael J. Wysocki's avatar Rafael J. Wysocki Committed by Greg Kroah-Hartman
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cpuidle: governors: menu: Avoid using invalid recent intervals data

[ Upstream commit fa3fa55d ]

Marc has reported that commit 85975dae ("cpuidle: menu: Avoid
discarding useful information") caused the number of wakeup interrupts
to increase on an idle system [1], which was not expected to happen
after merely allowing shallower idle states to be selected by the
governor in some cases.

However, on the system in question, all of the idle states deeper than
WFI are rejected by the driver due to a firmware issue [2].  This causes
the governor to only consider the recent interval duriation data
corresponding to attempts to enter WFI that are successful and the
recent invervals table is filled with values lower than the scheduler
tick period.  Consequently, the governor predicts an idle duration
below the scheduler tick period length and avoids stopping the tick
more often which leads to the observed symptom.

Address it by modifying the governor to update the recent intervals
table also when entering the previously selected idle state fails, so
it knows that the short idle intervals might have been the minority
had the selected idle states been actually entered every time.

Fixes: 85975dae ("cpuidle: menu: Avoid discarding useful information")
Link: https://lore.kernel.org/linux-pm/86o6sv6n94.wl-maz@kernel.org/ [1]
Link: https://lore.kernel.org/linux-pm/7ffcb716-9a1b-48c2-aaa4-469d0df7c792@arm.com/

 [2]
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: default avatarChristian Loehle <christian.loehle@arm.com>
Tested-by: default avatarMarc Zyngier <maz@kernel.org>
Reviewed-by: default avatarChristian Loehle <christian.loehle@arm.com>
Link: https://patch.msgid.link/2793874.mvXUDI8C0e@rafael.j.wysocki


Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent a8df217c
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