linux-kernel - [PATCH 0/2] alarmtimer: Rework the suspend flow in alarmtimer

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Message-ID: <20240207100619.3947442-1-pranavpp@google.com>
Date: Wed,  7 Feb 2024 10:06:17 +0000
From: Pranav Prasad <pranavpp@...gle.com>
To: tglx@...utronix.de, jstultz@...gle.com, sboyd@...nel.org
Cc: linux-kernel@...r.kernel.org, Pranav Prasad <pranavpp@...gle.com>
Subject: [PATCH 0/2] alarmtimer: Rework the suspend flow in alarmtimer

Hi!

During the driver suspend phase of kernel suspend, alarmtimer's suspend
callback is invoked and it identifies the earliest next wakeup alarm and
programs that into the HW real time clock (RTC). However, there is an
exception to this process. If the next alarm is within the next 2 seconds,
the alarmtimer driver fails to suspend. In this case, a non-trivial amount
of power is spent to freeze and unfreeze all userspace processes and to
suspend and resume a number of devices. In the vast majority of cases, the
imminent alarm that caused the failure was likely already scheduled before
suspend even started. This provides an opportunity to reduce power
consumption if the suspend failure decision is made earlier in the suspend
flow before the unnecessary extra work is done. This patch series aims to
achieve a kernel suspend flow in which the check for an imminent alarm is
performed early during the suspend prepare phase.

Pranav Prasad (2):
  alarmtimer: Create alarmtimer sysfs to make duration of kernel suspend
    check configurable
  alarmtimer: Modify alarmtimer suspend callback to check for imminent
    alarm using PM notifier

 kernel/time/alarmtimer.c | 178 +++++++++++++++++++++++++++++++--------
 1 file changed, 144 insertions(+), 34 deletions(-)

-- 
2.43.0.594.gd9cf4e227d-goog