ACPI: PM: Add HP EliteBook 855 G7 WWAN modem power resource quirk

This laptop (and possibly similar models too) has power resource called
"GP12.PXP_" for its Intel XMM7360 WWAN modem.

For this power resource to turn ON power for the modem it needs certain
internal flag called "ONEN" to be set:

Method (_ON, 0, NotSerialized) // _ON_: Power On
{
	If (^^^LPCB.EC0.ECRG)
	{
		If ((ONEN == Zero))
		{
                        Return (Zero)
		}
(..)
	}
}

This flag only gets set from this power resource _OFF method, while
the actual modem power gets turned off during suspend by "GP12.PTS"
method called from the global _PTS (Prepare To Sleep) method.

In fact, this power resource _OFF method implementation just sets the
aforementioned flag:

Method (_OFF, 0, NotSerialized) // _OFF: Power Off
{
	OFEN = Zero
	ONEN = One
}

Upon hibernation finish, the kernel tries to set this power resource
back ON since its _STA method returns 0 and the resource is still
considered in use as it is declared as required for D0 for both the
modem ACPI device (GP12.PWAN) and its parent PCIe port ACPI device
object (GP12).  But the _ON method won't do anything since that "ONEN"
flag is not set.

Overall, this means the modem is dead after hibernation finish until the
laptop is rebooted since the modem power has been cut by _PTS and its
PCI configuration was lost and not able to be restored.

The easiest way to workaround this issue is to call this power resource
_OFF method before calling the _ON method to make sure the "ONEN" flag
gets properly set.

This makes the modem alive once again after hibernation finish - with
properly restored PCI configuration space.

Since this platform does *not* support S3 the fact that
acpi_resume_power_resources() is also called during resume from S3 is
not a problem there.

Do the DMI based quirk matching and quirk flag initialization just
once - in acpi_power_resources_init() function.

This way the whole resume path overhead of this change on other systems
amounts to simple hp_eb_gp12pxp_quirk flag comparison.

Signed-off-by: Maciej S. Szmigiero <mail@maciej.szmigiero.name>
Link: https://patch.msgid.link/c6ff6931c5d27592052f30339de1b9cc298c43f0.1754243159.git.mail@maciej.szmigiero.name
[ rjw: Changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Author: maciejsszmigiero

drivers/acpi/power.c

@@ -23,6 +23,7 @@
 
 #define pr_fmt(fmt) "ACPI: PM: " fmt
 
+#include <linux/delay.h>
 #include <linux/dmi.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
@@ -63,6 +64,7 @@ struct acpi_power_resource_entry {
 	struct acpi_power_resource *resource;
 };
 
+static bool hp_eb_gp12pxp_quirk;
 static bool unused_power_resources_quirk;
 
 static LIST_HEAD(acpi_power_resource_list);
@@ -994,6 +996,38 @@ struct acpi_device *acpi_add_power_resource(acpi_handle handle)
 }
 
 #ifdef CONFIG_ACPI_SLEEP
+static bool resource_is_gp12pxp(acpi_handle handle)
+{
+	const char *path;
+	bool ret;
+
+	path = acpi_handle_path(handle);
+	ret = path && strcmp(path, "\\_SB_.PCI0.GP12.PXP_") == 0;
+	kfree(path);
+
+	return ret;
+}
+
+static void acpi_resume_on_eb_gp12pxp(struct acpi_power_resource *resource)
+{
+	acpi_handle_notice(resource->device.handle,
+			   "HP EB quirk - turning OFF then ON\n");
+
+	__acpi_power_off(resource);
+	__acpi_power_on(resource);
+
+	/*
+	 * Use the same delay as DSDT uses in modem _RST method.
+	 *
+	 * Otherwise we get "Unable to change power state from unknown to D0,
+	 * device inaccessible" error for the modem PCI device after thaw.
+	 *
+	 * This power resource is normally being enabled only during thaw (once)
+	 * so this wait is not a performance issue.
+	 */
+	msleep(200);
+}
+
 void acpi_resume_power_resources(void)
 {
 	struct acpi_power_resource *resource;
@@ -1015,8 +1049,14 @@ void acpi_resume_power_resources(void)
 
 		if (state == ACPI_POWER_RESOURCE_STATE_OFF
 		    && resource->ref_count) {
-			acpi_handle_debug(resource->device.handle, "Turning ON\n");
-			__acpi_power_on(resource);
+			if (hp_eb_gp12pxp_quirk &&
+			    resource_is_gp12pxp(resource->device.handle)) {
+				acpi_resume_on_eb_gp12pxp(resource);
+			} else {
+				acpi_handle_debug(resource->device.handle,
+						  "Turning ON\n");
+				__acpi_power_on(resource);
+			}
 		}
 
 		mutex_unlock(&resource->resource_lock);
@@ -1026,6 +1066,41 @@ void acpi_resume_power_resources(void)
 }
 #endif
 
+static const struct dmi_system_id dmi_hp_elitebook_gp12pxp_quirk[] = {
+/*
+ * This laptop (and possibly similar models too) has power resource called
+ * "GP12.PXP_" for its WWAN modem.
+ *
+ * For this power resource to turn ON power for the modem it needs certain
+ * internal flag called "ONEN" to be set.
+ * This flag only gets set from this power resource "_OFF" method, while the
+ * actual modem power gets turned off during suspend by "GP12.PTS" method
+ * called from the global "_PTS" (Prepare To Sleep) method.
+ * On the other hand, this power resource "_OFF" method implementation just
+ * sets the aforementioned flag without actually doing anything else (it
+ * doesn't contain any code to actually turn off power).
+ *
+ * The above means that when upon hibernation finish we try to set this
+ * power resource back ON since its "_STA" method returns 0 (while the resource
+ * is still considered in use) its "_ON" method won't do anything since
+ * that "ONEN" flag is not set.
+ * Overall, this means the modem is dead until laptop is rebooted since its
+ * power has been cut by "_PTS" and its PCI configuration was lost and not able
+ * to be restored.
+ *
+ * The easiest way to workaround the issue is to call this power resource
+ * "_OFF" method before calling the "_ON" method to make sure the "ONEN"
+ * flag gets properly set.
+ */
+	{
+		.matches = {
+			DMI_MATCH(DMI_SYS_VENDOR, "HP"),
+			DMI_MATCH(DMI_PRODUCT_NAME, "HP EliteBook 855 G7 Notebook PC"),
+		},
+	},
+	{}
+};
+
 static const struct dmi_system_id dmi_leave_unused_power_resources_on[] = {
 	{
 		/*
@@ -1070,6 +1145,7 @@ void acpi_turn_off_unused_power_resources(void)
 
 void __init acpi_power_resources_init(void)
 {
+	hp_eb_gp12pxp_quirk = dmi_check_system(dmi_hp_elitebook_gp12pxp_quirk);
 	unused_power_resources_quirk =
 		dmi_check_system(dmi_leave_unused_power_resources_on);
 }