1 files changed, 30 insertions, 0 deletions

diff --git a/drivers/w1/slaves/w1_ds2408.c b/drivers/w1/slaves/w1_ds2408.c
index 91cc2cdf02c0..cb8a8e5d9573 100644
--- a/drivers/w1/slaves/w1_ds2408.c
+++ b/drivers/w1/slaves/w1_ds2408.c
@@ -302,7 +302,33 @@ error:
         return -EIO;
 }
 
+/*
+ * This is a special sequence we must do to ensure the P0 output is not stuck
+ * in test mode. This is described in rev 2 of the ds2408's datasheet
+ * (http://datasheets.maximintegrated.com/en/ds/DS2408.pdf) under
+ * "APPLICATION INFORMATION/Power-up timing".
+ */
+static int w1_f29_disable_test_mode(struct w1_slave *sl)
+{
+        int res;
+        u8 magic[10] = {0x96, };
+        u64 rn = le64_to_cpu(*((u64*)&sl->reg_num));
+
+        memcpy(&magic[1], &rn, 8);
+        magic[9] = 0x3C;
+
+        mutex_lock(&sl->master->bus_mutex);
 
+        res = w1_reset_bus(sl->master);
+        if (res)
+                goto out;
+        w1_write_block(sl->master, magic, ARRAY_SIZE(magic));
+
+        res = w1_reset_bus(sl->master);
+out:
+        mutex_unlock(&sl->master->bus_mutex);
+        return res;
+}
 
 static struct bin_attribute w1_f29_sysfs_bin_files[] = {
         {
@@ -363,6 +389,10 @@ static int w1_f29_add_slave(struct w1_slave *sl)
         int err = 0;
         int i;
 
+        err = w1_f29_disable_test_mode(sl);
+        if (err)
+                return err;
+
         for (i = 0; i < ARRAY_SIZE(w1_f29_sysfs_bin_files) && !err; ++i)
                 err = sysfs_create_bin_file(
                         &sl->dev.kobj,