ACPI: Add _DEP support to fix battery issue on Asus T100TA

ACPI 5.0 introduces _DEP (Operation Region Dependencies) to designate
device objects that OSPM should assign a higher priority in start
ordering due to future operation region accesses.

On Asus T100TA, ACPI battery info are read from a I2C slave device via
I2C operation region. Before I2C operation region handler is installed,
battery _STA always returns 0. There is a _DEP method of designating
start order under battery device node.

This patch is to implement _DEP feature to fix battery issue on the
Asus T100TA.  Introducing acpi_dep_list and adding dep_unmet count
in struct acpi_device. During ACPI namespace scan, create struct
acpi_dep_data for a valid pair of master (device pointed to by _DEP)/
slave(device with _DEP), record master's and slave's ACPI handle in
it and put it into acpi_dep_list. The dep_unmet count will increase
by one if there is a device under its _DEP. Driver's probe() should
return EPROBE_DEFER when find dep_unmet is larger than 0. When I2C
operation region handler is installed, remove all struct acpi_dep_data
on the acpi_dep_list whose master is pointed to I2C host controller
and decrease slave's dep_unmet. When dep_unmet decreases to 0, all
_DEP conditions are met and then do acpi_bus_attach() for the device
in order to resolve battery _STA issue on the Asus T100TA.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=69011
Tested-by: Jan-Michael Brummer <jan.brummer@tabos.org>
Tested-by: Adam Williamson <adamw@happyassassin.net>
Tested-by: Michael Shigorin <shigorin@gmail.com>
Acked-by: Wolfram Sang <wsa@the-dreams.de>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

3 files changed, 90 insertions, 0 deletions

diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
index 8ec8a89a20ab..d98ba4355819 100644
--- a/drivers/acpi/battery.c
+++ b/drivers/acpi/battery.c
@@ -1180,6 +1180,10 @@ static int acpi_battery_add(struct acpi_device *device)
 
         if (!device)
                 return -EINVAL;
+
+        if (device->dep_unmet)
+                return -EPROBE_DEFER;
+
         battery = kzalloc(sizeof(struct acpi_battery), GFP_KERNEL);
         if (!battery)
                 return -ENOMEM;
diff --git a/drivers/acpi/scan.c b/drivers/acpi/scan.c
index 0476e90b2091..00189ad63c8f 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -36,6 +36,8 @@ bool acpi_force_hot_remove;
 
 static const char *dummy_hid = "device";
 
+static LIST_HEAD(acpi_dep_list);
+static DEFINE_MUTEX(acpi_dep_list_lock);
 static LIST_HEAD(acpi_bus_id_list);
 static DEFINE_MUTEX(acpi_scan_lock);
 static LIST_HEAD(acpi_scan_handlers_list);
@@ -43,6 +45,12 @@ DEFINE_MUTEX(acpi_device_lock);
 LIST_HEAD(acpi_wakeup_device_list);
 static DEFINE_MUTEX(acpi_hp_context_lock);
 
+struct acpi_dep_data {
+        struct list_head node;
+        acpi_handle master;
+        acpi_handle slave;
+};
+
 struct acpi_device_bus_id{
         char bus_id[15];
         unsigned int instance_no;
@@ -2086,6 +2094,59 @@ static void acpi_scan_init_hotplug(struct acpi_device *adev)
         }
 }
 
+static void acpi_device_dep_initialize(struct acpi_device *adev)
+{
+        struct acpi_dep_data *dep;
+        struct acpi_handle_list dep_devices;
+        acpi_status status;
+        int i;
+
+        if (!acpi_has_method(adev->handle, "_DEP"))
+                return;
+
+        status = acpi_evaluate_reference(adev->handle, "_DEP", NULL,
+                                        &dep_devices);
+        if (ACPI_FAILURE(status)) {
+                dev_err(&adev->dev, "Failed to evaluate _DEP.\n");
+                return;
+        }
+
+        for (i = 0; i < dep_devices.count; i++) {
+                struct acpi_device_info *info;
+                int skip;
+
+                status = acpi_get_object_info(dep_devices.handles[i], &info);
+                if (ACPI_FAILURE(status)) {
+                        dev_err(&adev->dev, "Error reading device info\n");
+                        continue;
+                }
+
+                /*
+                 * Skip the dependency of Windows System Power
+                 * Management Controller
+                 */
+                skip = info->valid & ACPI_VALID_HID &&
+                        !strcmp(info->hardware_id.string, "INT3396");
+
+                kfree(info);
+
+                if (skip)
+                        continue;
+
+                dep = kzalloc(sizeof(struct acpi_dep_data), GFP_KERNEL);
+                if (!dep)
+                        return;
+
+                dep->master = dep_devices.handles[i];
+                dep->slave  = adev->handle;
+                adev->dep_unmet++;
+
+                mutex_lock(&acpi_dep_list_lock);
+                list_add_tail(&dep->node , &acpi_dep_list);
+                mutex_unlock(&acpi_dep_list_lock);
+        }
+}
+
 static acpi_status acpi_bus_check_add(acpi_handle handle, u32 lvl_not_used,
                                       void *not_used, void **return_value)
 {
@@ -2112,6 +2173,7 @@ static acpi_status acpi_bus_check_add(acpi_handle handle, u32 lvl_not_used,
                 return AE_CTRL_DEPTH;
 
         acpi_scan_init_hotplug(device);
+        acpi_device_dep_initialize(device);
 
  out:
         if (!*return_value)
@@ -2232,6 +2294,29 @@ static void acpi_bus_attach(struct acpi_device *device)
                 device->handler->hotplug.notify_online(device);
 }
 
+void acpi_walk_dep_device_list(acpi_handle handle)
+{
+        struct acpi_dep_data *dep, *tmp;
+        struct acpi_device *adev;
+
+        mutex_lock(&acpi_dep_list_lock);
+        list_for_each_entry_safe(dep, tmp, &acpi_dep_list, node) {
+                if (dep->master == handle) {
+                        acpi_bus_get_device(dep->slave, &adev);
+                        if (!adev)
+                                continue;
+
+                        adev->dep_unmet--;
+                        if (!adev->dep_unmet)
+                                acpi_bus_attach(adev);
+                        list_del(&dep->node);
+                        kfree(dep);
+                }
+        }
+        mutex_unlock(&acpi_dep_list_lock);
+}
+EXPORT_SYMBOL_GPL(acpi_walk_dep_device_list);
+
 /**
  * acpi_bus_scan - Add ACPI device node objects in a given namespace scope.
  * @handle: Root of the namespace scope to scan.
diff --git a/drivers/i2c/i2c-core.c b/drivers/i2c/i2c-core.c
index f43b4e11647a..68aeb8eedae0 100644
--- a/drivers/i2c/i2c-core.c
+++ b/drivers/i2c/i2c-core.c
@@ -403,6 +403,7 @@ static int acpi_i2c_install_space_handler(struct i2c_adapter *adapter)
                 return -ENOMEM;
         }
 
+        acpi_walk_dep_device_list(handle);
         return 0;
 }