linux-kernel - Re: [PATCH v5] ACPI / Sleep: Check low power idle constraints for debug only

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Date:   Tue, 22 Aug 2017 15:08:44 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
Cc:     lenb@...nel.org, linux-pm@...r.kernel.org,
        mario.limonciello@...l.com, linux-kernel@...r.kernel.org,
        linux-acpi@...r.kernel.org
Subject: Re: [PATCH v5] ACPI / Sleep: Check low power idle constraints for debug only

On Wednesday, August 16, 2017 3:16:59 AM CEST Srinivas Pandruvada wrote:
> For SoC to achieve its lowest power platform idle state a set of hardware
> preconditions must be met. These preconditions or constraints can be
> obtained by issuing a device specific method (_DSM) with function "1".
> Refer to the document provided in the link below.
> 
> Here during initialization (from attach() callback of LPS0 device), invoke
> function 1 to get the device constraints. Each enabled constraint is
> stored in a table.
> 
> The devices in this table are used to check whether they were in required
> minimum state, while entering suspend. This check is done from platform
> freeze wake() callback, only when /sys/power/pm_debug_messages attribute
> is non zero.
> 
> If any constraint is not met and device is ACPI power managed then it
> prints the device information to kernel logs.
> 
> Also if debug is enabled in acpi/sleep.c, the constraint table and state
> of each device on wake is dumped in kernel logs.
> 
> Since pm_debug_messages_on setting is used as condition to check
> constraints outside kernel/power/main.c, pm_debug_messages_on is changed
> to a global variable.
> 
> Link: http://www.uefi.org/sites/default/files/resources/Intel_ACPI_Low_Power_S0_Idle.pdf
> Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>

Applied, thanks!