[PATCH V3] ACPI/Battery: Retry to get Battery information if failed during probing

[Lan Tianyu <tianyu.lan@intel.com>]

Some machines'(E,G Lenovo Z480) ECs are not stable during boot up
and causes battery driver fails to be loaded due to failure of getting
battery information from EC sometimes. After several retries, the
operation will work. This patch is to retry to get battery information 5
times if the first try fails.

Reported-and-tested-by: naszar <naszar@ya.ru>
Reference: https://bugzilla.kernel.org/show_bug.cgi?id=75581
Cc: stable@vger.kernel.org
Signed-off-by: Lan Tianyu <tianyu.lan@intel.com>
---
Change since V1:
	Change code style and add a comment.

Change since V2:
	Change code style.

 drivers/acpi/battery.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/drivers/acpi/battery.c b/drivers/acpi/battery.c
index e48fc98..cee5ee8 100644
--- a/drivers/acpi/battery.c
+++ b/drivers/acpi/battery.c
@@ -34,6 +34,7 @@
 #include <linux/dmi.h>
 #include <linux/slab.h>
 #include <linux/suspend.h>
+#include <linux/delay.h>
 #include <asm/unaligned.h>
 
 #ifdef CONFIG_ACPI_PROCFS_POWER
@@ -1117,6 +1118,28 @@ static struct dmi_system_id bat_dmi_table[] = {
 	{},
 };
 
+/*
+ * Some machines'(E,G Lenovo Z480) ECs are not stable
+ * during boot up and this causes battery driver fails to be
+ * probed due to failure of getting battery information
+ * from EC sometimes. After several retries, the operation
+ * may work. So add retry code here and 20ms sleep between
+ * every retries.
+ */
+static int acpi_battery_update_retry(struct acpi_battery *battery)
+{
+	int retry, ret;
+
+	for (retry = 5; retry; retry--) {
+		ret = acpi_battery_update(battery, false);
+		if (!ret)
+			break;
+
+		msleep(20);
+	}
+	return ret;
+}
+
 static int acpi_battery_add(struct acpi_device *device)
 {
 	int result = 0;
@@ -1135,9 +1158,11 @@ static int acpi_battery_add(struct acpi_device *device)
 	mutex_init(&battery->sysfs_lock);
 	if (acpi_has_method(battery->device->handle, "_BIX"))
 		set_bit(ACPI_BATTERY_XINFO_PRESENT, &battery->flags);
-	result = acpi_battery_update(battery, false);
+
+	result = acpi_battery_update_retry(battery);
 	if (result)
 		goto fail;
+
 #ifdef CONFIG_ACPI_PROCFS_POWER
 	result = acpi_battery_add_fs(device);
 #endif
-- 
1.8.4.rc0.1.g8f6a3e5.dirty