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authorAlexandre Belloni <alexandre.belloni@free-electrons.com>2016-03-21 15:58:38 +0100
committerAlexandre Belloni <alexandre.belloni@free-electrons.com>2016-03-25 02:38:59 +0100
commit85062c9b990b1dc8bbb8971ee7d3044a999cf25f (patch)
treed801d95e05e74855464d708de925a2716c5779f9
parent7f8a58925b4c0198c12344025b6ffd5dd7d9f1f5 (diff)
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>
-rw-r--r--drivers/rtc/rtc-rv8803.c28
1 files changed, 22 insertions, 6 deletions
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 @@ static irqreturn_t rv8803_handle_irq(int irq, void *dev_id)
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 @@ static int rv8803_probe(struct i2c_client *client,
{
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 @@ static int rv8803_probe(struct i2c_client *client,
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 @@ static int rv8803_probe(struct i2c_client *client,
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;