i2c: rtl9300: Increase timeout for transfer polling

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 implements
the ETIMEDOUT error, it is more sensible to increase the timeout in such a
way that communication with the (quite common) Realtek I2C-connected POE
management solution is possible.

[1] https://git.openwrt.org/?p=openwrt/openwrt.git;a=blob;f=target/linux/realtek/files-6.12/drivers/i2c/busses/i2c-rtl9300.c;h=c4d973195ef39dc56d6207e665d279745525fcac#l202

Fixes: c366be7 ("i2c: Add driver for the RTL9300 I2C controller")
Signed-off-by: Sven Eckelmann <[email protected]>
Cc: <[email protected]> # v6.13+
Reviewed-by: Chris Packham <[email protected]>
Tested-by: Chris Packham <[email protected]>
Signed-off-by: Andi Shyti <[email protected]>
Link: https://lore.kernel.org/r/[email protected]

Author: ecsv

drivers/i2c/busses/i2c-rtl9300.c

@@ -175,7 +175,7 @@ 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;