The timeout for transfers was only set to 2ms. Because of this relatively low limit, 12-byte read operations to the frontend MCU of a RTL8239 POE PSE chip cluster was consistently resulting in a timeout.
The original OpenWrt downstream driver [1] was not using any timeout limit at all. This is also possible by setting the timeout_us parameter of regmap_read_poll_timeout() to 0. But since the driver currently is implements the ETIMEDOUT error, it is more sensible to increase the timeout in such a way that the communication with the (quite common) Realtek I2C-connected POE management solution is possible.
[1] https://git.openwrt.org/?p=openwrt/openwrt.git%3Ba=blob%3Bf=target/linux/rea...
Cc: stable@vger.kernel.org Fixes: c366be720235 ("i2c: Add driver for the RTL9300 I2C controller") Signed-off-by: Sven Eckelmann sven@narfation.org Reviewed-by: Chris Packham chris.packham@alliedtelesis.co.nz Tested-by: Chris Packham chris.packham@alliedtelesis.co.nz --- drivers/i2c/busses/i2c-rtl9300.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/i2c/busses/i2c-rtl9300.c b/drivers/i2c/busses/i2c-rtl9300.c index 616d13e6d7088d2b5dc94dca13486caf10fc43f3..b8e8f416c5658058819dc0c75af7aa5f18f3f7a9 100644 --- a/drivers/i2c/busses/i2c-rtl9300.c +++ b/drivers/i2c/busses/i2c-rtl9300.c @@ -178,7 +178,7 @@ static int rtl9300_i2c_execute_xfer(struct rtl9300_i2c *i2c, char read_write, return ret;
ret = regmap_read_poll_timeout(i2c->regmap, i2c->reg_base + RTL9300_I2C_MST_CTRL1, - val, !(val & RTL9300_I2C_MST_CTRL1_I2C_TRIG), 100, 2000); + val, !(val & RTL9300_I2C_MST_CTRL1_I2C_TRIG), 100, 100000); if (ret) return ret;