linux-kernel - [PATCH v9 1/7] ACPI: scan: Obtain device's desired enumeration power state

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Date:   Fri, 29 Jan 2021 01:27:23 +0200
From:   Sakari Ailus <sakari.ailus@...ux.intel.com>
To:     linux-i2c@...r.kernel.org
Cc:     Wolfram Sang <wsa@...-dreams.de>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        rajmohan.mani@...el.com, Tomasz Figa <tfiga@...omium.org>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Bingbu Cao <bingbu.cao@...el.com>,
        Chiranjeevi Rapolu <chiranjeevi.rapolu@...el.com>,
        Hyungwoo Yang <hyungwoo.yang@...el.com>,
        linux-media@...r.kernel.org
Subject: [PATCH v9 1/7] ACPI: scan: Obtain device's desired enumeration power state

Store a device's desired enumeration power state in struct
acpi_device_power_flags during acpi_device object's initialisation.

Signed-off-by: Sakari Ailus <sakari.ailus@...ux.intel.com>
---
 drivers/acpi/scan.c     | 6 ++++++
 include/acpi/acpi_bus.h | 3 ++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 1d7a02ee45e05..b077c645c9845 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -987,6 +987,8 @@ static void acpi_bus_init_power_state(struct acpi_device *device, int state)
 
 static void acpi_bus_get_power_flags(struct acpi_device *device)
 {
+	unsigned long long pre;
+	acpi_status status;
 	u32 i;
 
 	/* Presence of _PS0|_PR0 indicates 'power manageable' */
@@ -1008,6 +1010,10 @@ static void acpi_bus_get_power_flags(struct acpi_device *device)
 	if (acpi_has_method(device->handle, "_DSW"))
 		device->power.flags.dsw_present = 1;
 
+	status = acpi_evaluate_integer(device->handle, "_PRE", NULL, &pre);
+	if (ACPI_SUCCESS(status) && !pre)
+		device->power.flags.allow_low_power_probe = 1;
+
 	/*
 	 * Enumerate supported power management states
 	 */
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index 02a716a0af5d4..020b850120883 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -258,7 +258,8 @@ struct acpi_device_power_flags {
 	u32 power_removed:1;	/* Optimize Dx->D0 */
 	u32 ignore_parent:1;	/* Power is independent of parent power state */
 	u32 dsw_present:1;	/* _DSW present? */
-	u32 reserved:26;
+	u32 allow_low_power_probe:1; /* Allow low power state in device probe */
+	u32 reserved:25;
 };
 
 struct acpi_device_power_state {
-- 
2.20.1