[PATCH v2 1/7] ASoC: apple: mca: increase SERDES reset delay

[James Calligeros]

The SERDES clusters in this peripheral take a long time to warm up.
We tried polling the reset bit until cleared, however this is not
a reliable signal of readiness to be configured. Only waiting
~25 us to give the cluster a chance to settle makes it work
reliably.

Increase the 2 us delay to 25 us and hope we never have to do this
again.

Fixes: d8b3e396088d ("ASoC: apple: mca: Fix SERDES reset sequence")
Signed-off-by: James Calligeros <jcalligeros99@xxxxxxxxx>
---
 sound/soc/apple/mca.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/sound/soc/apple/mca.c b/sound/soc/apple/mca.c
index 492165c0e1ea..ebe116f32661 100644
--- a/sound/soc/apple/mca.c
+++ b/sound/soc/apple/mca.c
@@ -210,10 +210,10 @@ static void mca_fe_early_trigger(struct snd_pcm_substream *substream, int cmd,
 			   SERDES_STATUS_EN | SERDES_STATUS_RST,
 			   SERDES_STATUS_RST);
 		/*
-		 * Experiments suggest that it takes at most ~1 us
-		 * for the bit to clear, so wait 2 us for good measure.
+		 * The SERDES cluster needs a bit of time to reset itself
+		 * and settle before we start poking it. This is... slow...
 		 */
-		udelay(2);
+		udelay(25);
 		WARN_ON(readl_relaxed(cl->base + serdes_unit + REG_SERDES_STATUS) &
 			SERDES_STATUS_RST);
 		mca_modify(cl, serdes_conf, SERDES_CONF_SYNC_SEL,

-- 
2.54.0