[alsa-devel] [PATCH] ASoC: arizona: Poll for FLL clock OK rather than use interrupts

[Charles Keepax]

The extcon driver takes the DAPM mutex from within the interrupt thread
in several places, which makes it possible to get into a situation where
the interrupt thread is blocked waiting on the DAPM mutex whilst a DAPM
sequence is running which is attempting to configure the FLL. In this
case the FLL completion can't be completed as as the IRQ handler is
ONE_SHOT, which cause the FLL lock to use the full time out (250mS) and
report that the process timed out.

It is not really practical to make the extcon driver not take the DAPM
mutex from within the interrupt thread, at least not without extensive
modification. So this patch fixes the issue by switching the wait for
the FLL lock to polling. A few fast polls are done first as the FLL
should lock quickly for a good quality reference clock, (indeed it hits
on the first poll on my system) and it will poll every 20mS after that
until it times out.

Signed-off-by: Charles Keepax <ckeepax at opensource.wolfsonmicro.com>
---
 sound/soc/codecs/arizona.c |   47 +++++++++++++++++--------------------------
 sound/soc/codecs/arizona.h |    1 -
 2 files changed, 19 insertions(+), 29 deletions(-)

diff --git a/sound/soc/codecs/arizona.c b/sound/soc/codecs/arizona.c
index 42b2021..8a2221a 100644
--- a/sound/soc/codecs/arizona.c
+++ b/sound/soc/codecs/arizona.c
@@ -1756,17 +1756,6 @@ int arizona_init_dai(struct arizona_priv *priv, int id)
 }
 EXPORT_SYMBOL_GPL(arizona_init_dai);
 
-static irqreturn_t arizona_fll_clock_ok(int irq, void *data)
-{
-	struct arizona_fll *fll = data;
-
-	arizona_fll_dbg(fll, "clock OK\n");
-
-	complete(&fll->ok);
-
-	return IRQ_HANDLED;
-}
-
 static struct {
 	unsigned int min;
 	unsigned int max;
@@ -2048,10 +2037,11 @@ static int arizona_is_enabled_fll(struct arizona_fll *fll)
 static int arizona_enable_fll(struct arizona_fll *fll)
 {
 	struct arizona *arizona = fll->arizona;
-	unsigned long time_left;
 	bool use_sync = false;
 	int already_enabled = arizona_is_enabled_fll(fll);
 	struct arizona_fll_cfg cfg;
+	int i;
+	unsigned int val;
 
 	if (already_enabled < 0)
 		return already_enabled;
@@ -2110,9 +2100,6 @@ static int arizona_enable_fll(struct arizona_fll *fll)
 	if (!already_enabled)
 		pm_runtime_get(arizona->dev);
 
-	/* Clear any pending completions */
-	try_wait_for_completion(&fll->ok);
-
 	regmap_update_bits_async(arizona->regmap, fll->base + 1,
 				 ARIZONA_FLL1_ENA, ARIZONA_FLL1_ENA);
 	if (use_sync)
@@ -2124,10 +2111,24 @@ static int arizona_enable_fll(struct arizona_fll *fll)
 		regmap_update_bits_async(arizona->regmap, fll->base + 1,
 					 ARIZONA_FLL1_FREERUN, 0);
 
-	time_left = wait_for_completion_timeout(&fll->ok,
-					  msecs_to_jiffies(250));
-	if (time_left == 0)
+	arizona_fll_dbg(fll, "Waiting for FLL lock...\n");
+	val = 0;
+	for (i = 0; i < 15; i++) {
+		if (i < 5)
+			usleep_range(200, 400);
+		else
+			msleep(20);
+
+		regmap_read(arizona->regmap,
+			    ARIZONA_INTERRUPT_RAW_STATUS_5,
+			    &val);
+		if (val & (ARIZONA_FLL1_CLOCK_OK_STS << (fll->id - 1)))
+			break;
+	}
+	if (i == 15)
 		arizona_fll_warn(fll, "Timed out waiting for lock\n");
+	else
+		arizona_fll_dbg(fll, "FLL locked (%d polls)\n", i);
 
 	return 0;
 }
@@ -2212,11 +2213,8 @@ EXPORT_SYMBOL_GPL(arizona_set_fll);
 int arizona_init_fll(struct arizona *arizona, int id, int base, int lock_irq,
 		     int ok_irq, struct arizona_fll *fll)
 {
-	int ret;
 	unsigned int val;
 
-	init_completion(&fll->ok);
-
 	fll->id = id;
 	fll->base = base;
 	fll->arizona = arizona;
@@ -2238,13 +2236,6 @@ int arizona_init_fll(struct arizona *arizona, int id, int base, int lock_irq,
 	snprintf(fll->clock_ok_name, sizeof(fll->clock_ok_name),
 		 "FLL%d clock OK", id);
 
-	ret = arizona_request_irq(arizona, ok_irq, fll->clock_ok_name,
-				  arizona_fll_clock_ok, fll);
-	if (ret != 0) {
-		dev_err(arizona->dev, "Failed to get FLL%d clock OK IRQ: %d\n",
-			id, ret);
-	}
-
 	regmap_update_bits(arizona->regmap, fll->base + 1,
 			   ARIZONA_FLL1_FREERUN, 0);
 
diff --git a/sound/soc/codecs/arizona.h b/sound/soc/codecs/arizona.h
index 13598b0..ada0a41 100644
--- a/sound/soc/codecs/arizona.h
+++ b/sound/soc/codecs/arizona.h
@@ -261,7 +261,6 @@ struct arizona_fll {
 	int id;
 	unsigned int base;
 	unsigned int vco_mult;
-	struct completion ok;
 
 	unsigned int fout;
 	int sync_src;
-- 
1.7.2.5