One remark below.
Met vriendelijke groet / kind regards,
Mike Looijmans
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On 11-03-2021 23:24, Robert Hancock wrote:
The Si5341 datasheet warns that before accessing any other registers,
including the PAGE register, we need to wait for the DEVICE_READY register
to indicate the device is ready, or the process of the device loading its
state from NVM can be corrupted. Wait for DEVICE_READY on startup before
continuing initialization. This is done using a raw I2C register read
prior to setting up regmap to avoid any potential unwanted automatic PAGE
register accesses from regmap at this stage.
Fixes: 3044a860fd ("clk: Add Si5341/Si5340 driver")
Signed-off-by: Robert Hancock <robert.hancock@xxxxxxxxxx>
---
drivers/clk/clk-si5341.c | 31 +++++++++++++++++++++++++++++++
1 file changed, 31 insertions(+)
diff --git a/drivers/clk/clk-si5341.c b/drivers/clk/clk-si5341.c
index e0446e66fa64..f210860fb96e 100644
--- a/drivers/clk/clk-si5341.c
+++ b/drivers/clk/clk-si5341.c
@@ -94,6 +94,7 @@ struct clk_si5341_output_config {
#define SI5341_STATUS 0x000C
#define SI5341_SOFT_RST 0x001C
#define SI5341_IN_SEL 0x0021
+#define SI5341_DEVICE_READY 0x00FE
#define SI5341_XAXB_CFG 0x090E
#define SI5341_IN_EN 0x0949
#define SI5341_INX_TO_PFD_EN 0x094A
@@ -1189,6 +1190,31 @@ static const struct regmap_range_cfg si5341_regmap_ranges[] = {
},
};
+static int si5341_wait_device_ready(struct i2c_client *client)
+{
+ int count;
+
+ /* Datasheet warns: Any attempt to read or write any register other
+ * than DEVICE_READY before DEVICE_READY reads as 0x0F may corrupt the
+ * NVM programming and may corrupt the register contents, as they are
+ * read from NVM. Note that this includes accesses to the PAGE register.
+ * Also: DEVICE_READY is available on every register page, so no page
+ * change is needed to read it.
+ * Do this outside regmap to avoid automatic PAGE register access.
+ */
+ for (count = 0; count < 10; ++count) {
+ s32 result = i2c_smbus_read_byte_data(client,
+ SI5341_DEVICE_READY);
+ if (result < 0)
+ return result;
+ if (result == 0x0F)
+ return 0;
+ usleep_range(1000, 20000);
+ }
+ dev_err(&client->dev, "timeout waiting for DEVICE_READY\n");
The "timeout" here is random between 10 and 200 milliseconds.
The datasheet says that the device may take 300ms to initialize, so I
guess 300 milliseconds would be a good timeout.
I'm also pretty sure there's a built-in kernel function to poll a
register with timeout that you should use here.
+ return -EIO;
+}
+
static const struct regmap_config si5341_regmap_config = {
.reg_bits = 8,
.val_bits = 8,
@@ -1385,6 +1411,11 @@ static int si5341_probe(struct i2c_client *client,
data->i2c_client = client;
+ /* Must be done before otherwise touching hardware */
+ err = si5341_wait_device_ready(client);
+ if (err)
+ return err;
+
for (i = 0; i < SI5341_NUM_INPUTS; ++i) {
input = devm_clk_get(&client->dev, si5341_input_clock_names[i]);
if (IS_ERR(input)) {
--
Mike Looijmans
