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-rw-r--r--drivers/w1/slaves/w1_ds2408.c30
1 files changed, 30 insertions, 0 deletions
diff --git a/drivers/w1/slaves/w1_ds2408.c b/drivers/w1/slaves/w1_ds2408.c
index 91cc2cd..cb8a8e5 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,
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