rtc: rv8803: workaround i2c HW issue
The rv8803 has a 60µs window where it will not answer on the i2c bus.
It also means there will be no ack for the communication. Make sure
communication is tried multiple times when this happens (the i2c subsystem
mandates -ENXIO is that case but the number of retries is host specific).
The critical parts are the probe function and the alarm callback so make
sure we handle the failure there.
Cc: stable@vger.kernel.org # v4.4
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
diff --git a/drivers/rtc/rtc-rv8803.c b/drivers/rtc/rtc-rv8803.c
index 8d9f35c..f623038 100644
--- a/drivers/rtc/rtc-rv8803.c
+++ b/drivers/rtc/rtc-rv8803.c
@@ -61,11 +61,14 @@
struct i2c_client *client = dev_id;
struct rv8803_data *rv8803 = i2c_get_clientdata(client);
unsigned long events = 0;
- int flags;
+ int flags, try = 0;
mutex_lock(&rv8803->flags_lock);
- flags = i2c_smbus_read_byte_data(client, RV8803_FLAG);
+ do {
+ flags = i2c_smbus_read_byte_data(client, RV8803_FLAG);
+ try++;
+ } while ((flags == -ENXIO) && (try < 3));
if (flags <= 0) {
mutex_unlock(&rv8803->flags_lock);
return IRQ_NONE;
@@ -424,7 +427,7 @@
{
struct i2c_adapter *adapter = to_i2c_adapter(client->dev.parent);
struct rv8803_data *rv8803;
- int err, flags;
+ int err, flags, try = 0;
if (!i2c_check_functionality(adapter, I2C_FUNC_SMBUS_BYTE_DATA |
I2C_FUNC_SMBUS_I2C_BLOCK)) {
@@ -441,7 +444,16 @@
rv8803->client = client;
i2c_set_clientdata(client, rv8803);
- flags = i2c_smbus_read_byte_data(client, RV8803_FLAG);
+ /*
+ * There is a 60µs window where the RTC may not reply on the i2c bus in
+ * that case, the transfer is not ACKed. In that case, ensure there are
+ * multiple attempts.
+ */
+ do {
+ flags = i2c_smbus_read_byte_data(client, RV8803_FLAG);
+ try++;
+ } while ((flags == -ENXIO) && (try < 3));
+
if (flags < 0)
return flags;
@@ -476,8 +488,12 @@
return PTR_ERR(rv8803->rtc);
}
- err = i2c_smbus_write_byte_data(rv8803->client, RV8803_EXT,
- RV8803_EXT_WADA);
+ try = 0;
+ do {
+ err = i2c_smbus_write_byte_data(rv8803->client, RV8803_EXT,
+ RV8803_EXT_WADA);
+ try++;
+ } while ((err == -ENXIO) && (try < 3));
if (err)
return err;