ASoC: wm8904: Don't touch GPIO configs set to 0xFFFF

When updating the GPIO registers, do nothing for all fields of gpio_cfg
that are "0xFFFF".

This "do nothing" flag used to be 0 to easily check whether the gpio_cfg
field was actually set inside pdata or left empty (default).

However, 0 is a valid configuration for these registers, while 0xFFFF is
not.

With this change, users can explicitly set them to 0.
Not setting gpio_cfg in the platform data will now lead to setting all
GPIO registers to 0 instead of leaving them unset.

No one is using this platform data with this codec.

The change gets the driver ready to properly set gpio_cfg from the DT.

Datasheet: https://statics.cirrus.com/pubs/proDatasheet/WM8904_Rev4.1.pdf
Signed-off-by: Ernest Van Hoecke <[email protected]>
Signed-off-by: Francesco Dolcini <[email protected]>
Reviewed-by: Charles Keepax <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Mark Brown <[email protected]>

Author: Ernest Van Hoecke

sound/soc/codecs/wm8904.c

@@ -2270,7 +2270,8 @@ static int wm8904_i2c_probe(struct i2c_client *i2c)
 	/* Apply configuration from the platform data. */
 	if (wm8904->pdata) {
 		for (i = 0; i < WM8904_GPIO_REGS; i++) {
-			if (!wm8904->pdata->gpio_cfg[i])
+			/* 0xFFFF in this config means "don't touch" */
+			if (wm8904->pdata->gpio_cfg[i] == 0xffff)
 				continue;
 
 			regmap_update_bits(wm8904->regmap,