Date:	Wed,  3 Feb 2016 19:04:20 +0800
From:	Chen Yu <yu.c.chen@...el.com>
To:	linux-acpi@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, rjw@...ysocki.net, lenb@...nel.org,
	rui.zhang@...el.com, bugzilla@...ess.net, cwhuang@...roid-x86.org,
	Chen Yu <yu.c.chen@...el.com>
Subject: [PATCH] ACPI / button: Avoid using broken _LID on Surface tablet

Some platforms such as Surface 3, Surface Pro 1 have broken _LID
that, either _LID returns 'closed' during bootup, or _LID fails
to return the up-to-date lid state to OSPM. This is because
that, on these platforms _LID is implemented by returning a
local variable, which can only be updated by lid events:

Device (LID)
{
	Name (LIDB, Zero)
	Method (_LID, 0, NotSerialized)
	{
		Return (LIDB)
	}
}

Method (_E4C, 0, Serialized)
{
	If ((HELD == One))
	{
		^^LID.LIDB = One
	}
	Else
	{
		^^LID.LIDB = Zero
		Notify (LID, 0x80)
	}
}

After the lid is closed, _E4C updates the LIDB to zero, then system
falls asleep, however when lid is opened, there would be no interrupt
triggered due to hardware design, we have to wake the system up by
pressing power button, as a result, LIDB remains zero after resumed,
thus _LID returns 'close' to systemd daemon(or does not return any
value to systemd), as a result the system suspends again even though
we do nothing.

This patch is to provide a possible workaround for these broken
platforms, by introducing a 'cached' lid state, which is not
based on evaluating _LID, but based on maintaining the lid
state in a event-driven manner:

1. lid cache state is assigned to 'open' explicitly during boot up.
2. lid cache state can only be changed during suspend/resume, or someone
   notifies the lid device.
3. always return lid cache state instead of _LID to sysfs.

Linked: https://bugzilla.kernel.org/show_bug.cgi?id=89211
Reported-and-tested-by: GiH <gih@...er.one>
Reported-by: David J. Goehrig <dave@...h.org>
Reported-by: Stephen Just <stephenjust@...il.com>
Signed-off-by: Chen Yu <yu.c.chen@...el.com>
---
 drivers/acpi/button.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 60 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/button.c b/drivers/acpi/button.c
index 5c3b091..ec2a027 100644
--- a/drivers/acpi/button.c
+++ b/drivers/acpi/button.c
@@ -28,6 +28,7 @@
 #include <linux/input.h>
 #include <linux/slab.h>
 #include <linux/acpi.h>
+#include <linux/dmi.h>
 #include <acpi/button.h>
 
 #define PREFIX "ACPI: "
@@ -53,6 +54,9 @@
 #define ACPI_BUTTON_DEVICE_NAME_LID	"Lid Switch"
 #define ACPI_BUTTON_TYPE_LID		0x05
 
+#define ACPI_LID_CACHE_OPEN			1
+#define ACPI_LID_CACHE_CLOSE			0
+
 #define _COMPONENT		ACPI_BUTTON_COMPONENT
 ACPI_MODULE_NAME("button");
 
@@ -101,8 +105,10 @@ struct acpi_button {
 	char phys[32];			/* for input device */
 	unsigned long pushed;
 	bool suspended;
+	unsigned long long cache_state;
 };
 
+static int use_lid_cache_state;
 static BLOCKING_NOTIFIER_HEAD(acpi_lid_notifier);
 static struct acpi_device *lid_device;
 
@@ -118,8 +124,13 @@ static int acpi_button_state_seq_show(struct seq_file *seq, void *offset)
 	struct acpi_device *device = seq->private;
 	acpi_status status;
 	unsigned long long state;
+	struct acpi_button *button = acpi_driver_data(device);
 
 	status = acpi_evaluate_integer(device->handle, "_LID", NULL, &state);
+
+	if (use_lid_cache_state)
+		state = button->cache_state;
+
 	seq_printf(seq, "state:      %s\n",
 		   ACPI_FAILURE(status) ? "unsupported" :
 			(state ? "open" : "closed"));
@@ -233,15 +244,23 @@ int acpi_lid_open(void)
 {
 	acpi_status status;
 	unsigned long long state;
+	struct acpi_button *button;
 
 	if (!lid_device)
 		return -ENODEV;
 
+	button = acpi_driver_data(lid_device);
+	if (!button)
+		return -ENODEV;
+
 	status = acpi_evaluate_integer(lid_device->handle, "_LID", NULL,
 				       &state);
 	if (ACPI_FAILURE(status))
 		return -ENODEV;
 
+	if (use_lid_cache_state)
+		state = button->cache_state;
+
 	return !!state;
 }
 EXPORT_SYMBOL(acpi_lid_open);
@@ -257,6 +276,9 @@ static int acpi_lid_send_state(struct acpi_device *device)
 	if (ACPI_FAILURE(status))
 		return -ENODEV;
 
+	if (use_lid_cache_state)
+		state = button->cache_state;
+
 	/* input layer checks if event is redundant */
 	input_report_switch(button->input, SW_LID, !state);
 	input_sync(button->input);
@@ -290,6 +312,8 @@ static void acpi_button_notify(struct acpi_device *device, u32 event)
 	case ACPI_BUTTON_NOTIFY_STATUS:
 		input = button->input;
 		if (button->type == ACPI_BUTTON_TYPE_LID) {
+			if (use_lid_cache_state)
+				button->cache_state = !button->cache_state;
 			acpi_lid_send_state(device);
 		} else {
 			int keycode;
@@ -325,6 +349,9 @@ static int acpi_button_suspend(struct device *dev)
 	struct acpi_button *button = acpi_driver_data(device);
 
 	button->suspended = true;
+	if (use_lid_cache_state)
+		button->cache_state = ACPI_LID_CACHE_CLOSE;
+
 	return 0;
 }
 
@@ -334,12 +361,41 @@ static int acpi_button_resume(struct device *dev)
 	struct acpi_button *button = acpi_driver_data(device);
 
 	button->suspended = false;
-	if (button->type == ACPI_BUTTON_TYPE_LID)
+	if (button->type == ACPI_BUTTON_TYPE_LID) {
+		if (use_lid_cache_state)
+			button->cache_state = ACPI_LID_CACHE_OPEN;
 		return acpi_lid_send_state(device);
+	}
 	return 0;
 }
 #endif
 
+static int switch_lid_mode(const struct dmi_system_id *d)
+{
+	use_lid_cache_state = 1;
+	return 0;
+}
+
+static struct dmi_system_id broken_lid_dmi_table[] = {
+	{
+	 .callback = switch_lid_mode,
+	 .ident = "Surface Pro 1",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Microsoft Corporation"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Surface with Windows 8 Pro"),
+		},
+	},
+	{
+	 .callback = switch_lid_mode,
+	 .ident = "Surface 3",
+	 .matches = {
+		DMI_MATCH(DMI_SYS_VENDOR, "Microsoft Corporation"),
+		DMI_MATCH(DMI_PRODUCT_NAME, "Surface 3"),
+		},
+	},
+	{}
+};
+
 static int acpi_button_add(struct acpi_device *device)
 {
 	struct acpi_button *button;
@@ -380,6 +436,7 @@ static int acpi_button_add(struct acpi_device *device)
 		strcpy(name, ACPI_BUTTON_DEVICE_NAME_LID);
 		sprintf(class, "%s/%s",
 			ACPI_BUTTON_CLASS, ACPI_BUTTON_SUBCLASS_LID);
+		dmi_check_system(broken_lid_dmi_table);
 	} else {
 		printk(KERN_ERR PREFIX "Unsupported hid [%s]\n", hid);
 		error = -ENODEV;
@@ -416,6 +473,8 @@ static int acpi_button_add(struct acpi_device *device)
 	if (error)
 		goto err_remove_fs;
 	if (button->type == ACPI_BUTTON_TYPE_LID) {
+		if (use_lid_cache_state)
+			button->cache_state = ACPI_LID_CACHE_OPEN;
 		acpi_lid_send_state(device);
 		/*
 		 * This assumes there's only one lid device, or if there are
-- 
1.8.4.2

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