ASoC: arizona: Add 32uS delay after putting FLL into freerun

When switching between two clock sources using the FLL freerun to smooth the transition we should wait 32uS after putting the FLL into freerun before we proceed. In practice we appear to be getting enough delay from the surrounding code, but better to make it explicit.

Quoted 4 lines · Charles Keepax

When switching between two clock sources using the FLL freerun to smooth the transition we should wait 32uS after putting the FLL into freerun before we proceed. In practice we appear to be getting enough delay from the surrounding code, but better to make it explicit.

You'll almost certainly get 32us from just setting up the I/O and also...

sound/soc/codecs/arizona.c static int arizona_enable_fll(struct arizona_fll *fll) · line 2218

Quoted 6 lines

+++ b/sound/soc/codecs/arizona.c

sound/soc/codecs/arizona.c +1 -0

@@ -2215,6 +2215,7 @@ static int arizona_enable_fll(struct arizona_fll *fll)
 		regmap_update_bits_async(fll->arizona->regmap, fll->base + 1,
 					 ARIZONA_FLL1_FREERUN,
 					 ARIZONA_FLL1_FREERUN);
+		udelay(32);

...this won't do what you say it will - the I/O is asynchronous so what this will do is add a delay immediately after scheduling the I/O while the I/O is at best in progress and most likely before it is ever begun. You'd need to make the I/O synchronous to actually introduce the delay.