linux-kernel - [PATCH v2 2/2] ACPI: power: Turn off unused power resources unconditionally

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Message-ID: <20994880.EfDdHjke4D@kreacher>
Date:   Thu, 18 Mar 2021 19:28:28 +0100
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Linux ACPI <linux-acpi@...r.kernel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        David Box <david.e.box@...ux.intel.com>
Subject: [PATCH v2 2/2] ACPI: power: Turn off unused power resources unconditionally

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

According to the ACPI specification (section 7.2.2 in ACPI 6.4), the
OS may evaluate the _OFF method of a power resource that is "off"
already [1], and in particular that can be done in the case of unused
power resources.

Accordingly, modify acpi_turn_off_unused_power_resources() to
evaluate the _OFF method for each of the unused power resources
unconditionally which may help to work around BIOS issues where the
return value of _STA for a power resource does not reflect the
actual state of the power resource [2].

Link: https://uefi.org/specs/ACPI/6.4/07_Power_and_Performance_Mgmt/declaring-a-power-resource-object.html#off # [1]
Link: https://lore.kernel.org/lkml/20210314000439.3138941-1-luzmaximilian@gmail.com/ # [2]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---

New patch in v2.

---
 drivers/acpi/power.c |   11 +----------
 1 file changed, 1 insertion(+), 10 deletions(-)

Index: linux-pm/drivers/acpi/power.c
===================================================================
--- linux-pm.orig/drivers/acpi/power.c
+++ linux-pm/drivers/acpi/power.c
@@ -1005,18 +1005,9 @@ void acpi_turn_off_unused_power_resource
 	mutex_lock(&power_resource_list_lock);
 
 	list_for_each_entry_reverse(resource, &acpi_power_resource_list, list_node) {
-		int result, state;
-
 		mutex_lock(&resource->resource_lock);
 
-		result = acpi_power_get_state(resource->device.handle, &state);
-		if (result) {
-			mutex_unlock(&resource->resource_lock);
-			continue;
-		}
-
-		if (state == ACPI_POWER_RESOURCE_STATE_ON
-		    && !resource->ref_count) {
+		if (!resource->ref_count) {
 			dev_info(&resource->device.dev, "Turning OFF\n");
 			__acpi_power_off(resource);
 		}