ALSA: hda: Manage concurrent reg access more properly

In the commit 8e85def5723e ("ALSA: hda: enable regmap internal
locking"), we re-enabled the regmap lock due to the reported
regression that showed the possible concurrent accesses.  It was a
temporary workaround, and there are still a few opened races even
after the revert.  In this patch, we cover those still opened windows
with a proper mutex lock and disable the regmap internal lock again.

First off, the patch introduces a new snd_hdac_device.regmap_lock
mutex that is applied for each snd_hdac_regmap_*() call, including
read, write and update helpers.  The mutex is applied carefully so
that it won't block the self-power-up procedure in the helper
function.  Also, this assures the protection for the accesses without
regmap, too.

The snd_hdac_regmap_update_raw() is refactored to use the standard
regmap_update_bits_check() function instead of the open-code.  The
non-regmap case is still open-coded but it's an easy part.  The all
read and write operations are in the single mutex protection, so it's
now race-free.

In addition, a couple of new helper functions are added:
snd_hdac_regmap_update_raw_once() and snd_hdac_regmap_sync().  Both
are called from HD-audio legacy driver.  The former is to initialize
the given verb bits but only once when it's not initialized yet.  Due
to this condition, the function invokes regcache_cache_only(), and
it's now performed inside the regmap_lock (formerly it was racy) too.
The latter function is for simply invoking regcache_sync() inside the
regmap_lock, which is called from the codec resume call path.
Along with that, the HD-audio codec driver code is slightly modified /
simplified to adapt those new functions.

And finally, snd_hdac_regmap_read_raw(), *_write_raw(), etc are
rewritten with the helper macro.  It's just for simplification because
the code logic is identical among all those functions.

Tested-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Link: https://lore.kernel.org/r/20200109090104.26073-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>

2 files changed, 108 insertions, 35 deletions

diff --git a/sound/hda/hdac_device.c b/sound/hda/hdac_device.c
index b4f8725f5ddf..7bcdb0e454f2 100644
--- a/sound/hda/hdac_device.c
+++ b/sound/hda/hdac_device.c
@@ -57,6 +57,7 @@ int snd_hdac_device_init(struct hdac_device *codec, struct hdac_bus *bus,
 	codec->addr = addr;
 	codec->type = HDA_DEV_CORE;
 	mutex_init(&codec->widget_lock);
+	mutex_init(&codec->regmap_lock);
 	pm_runtime_set_active(&codec->dev);
 	pm_runtime_get_noresume(&codec->dev);
 	atomic_set(&codec->in_pm, 0);
diff --git a/sound/hda/hdac_regmap.c b/sound/hda/hdac_regmap.c
index 0c8188a48a00..d75f31eb9d78 100644
--- a/sound/hda/hdac_regmap.c
+++ b/sound/hda/hdac_regmap.c
@@ -363,6 +363,7 @@ static const struct regmap_config hda_regmap_cfg = {
 	.reg_write = hda_reg_write,
 	.use_single_read = true,
 	.use_single_write = true,
+	.disable_locking = true,
 };
 
 /**
@@ -425,12 +426,29 @@ EXPORT_SYMBOL_GPL(snd_hdac_regmap_add_vendor_verb);
 static int reg_raw_write(struct hdac_device *codec, unsigned int reg,
 			 unsigned int val)
 {
+	int err;
+
+	mutex_lock(&codec->regmap_lock);
 	if (!codec->regmap)
-		return hda_reg_write(codec, reg, val);
+		err = hda_reg_write(codec, reg, val);
 	else
-		return regmap_write(codec->regmap, reg, val);
+		err = regmap_write(codec->regmap, reg, val);
+	mutex_unlock(&codec->regmap_lock);
+	return err;
 }
 
+/* a helper macro to call @func_call; retry with power-up if failed */
+#define CALL_RAW_FUNC(codec, func_call)				\
+	({							\
+		int _err = func_call;				\
+		if (_err == -EAGAIN) {				\
+			_err = snd_hdac_power_up_pm(codec);	\
+			if (_err >= 0)				\
+				_err = func_call;		\
+			snd_hdac_power_down_pm(codec);		\
+		}						\
+		_err;})
+
 /**
  * snd_hdac_regmap_write_raw - write a pseudo register with power mgmt
  * @codec: the codec object
@@ -442,42 +460,29 @@ static int reg_raw_write(struct hdac_device *codec, unsigned int reg,
 int snd_hdac_regmap_write_raw(struct hdac_device *codec, unsigned int reg,
 			      unsigned int val)
 {
-	int err;
-
-	err = reg_raw_write(codec, reg, val);
-	if (err == -EAGAIN) {
-		err = snd_hdac_power_up_pm(codec);
-		if (err >= 0)
-			err = reg_raw_write(codec, reg, val);
-		snd_hdac_power_down_pm(codec);
-	}
-	return err;
+	return CALL_RAW_FUNC(codec, reg_raw_write(codec, reg, val));
 }
 EXPORT_SYMBOL_GPL(snd_hdac_regmap_write_raw);
 
 static int reg_raw_read(struct hdac_device *codec, unsigned int reg,
 			unsigned int *val, bool uncached)
 {
+	int err;
+
+	mutex_lock(&codec->regmap_lock);
 	if (uncached || !codec->regmap)
-		return hda_reg_read(codec, reg, val);
+		err = hda_reg_read(codec, reg, val);
 	else
-		return regmap_read(codec->regmap, reg, val);
+		err = regmap_read(codec->regmap, reg, val);
+	mutex_unlock(&codec->regmap_lock);
+	return err;
 }
 
 static int __snd_hdac_regmap_read_raw(struct hdac_device *codec,
 				      unsigned int reg, unsigned int *val,
 				      bool uncached)
 {
-	int err;
-
-	err = reg_raw_read(codec, reg, val, uncached);
-	if (err == -EAGAIN) {
-		err = snd_hdac_power_up_pm(codec);
-		if (err >= 0)
-			err = reg_raw_read(codec, reg, val, uncached);
-		snd_hdac_power_down_pm(codec);
-	}
-	return err;
+	return CALL_RAW_FUNC(codec, reg_raw_read(codec, reg, val, uncached));
 }
 
 /**
@@ -504,6 +509,35 @@ int snd_hdac_regmap_read_raw_uncached(struct hdac_device *codec,
 	return __snd_hdac_regmap_read_raw(codec, reg, val, true);
 }
 
+static int reg_raw_update(struct hdac_device *codec, unsigned int reg,
+			  unsigned int mask, unsigned int val)
+{
+	unsigned int orig;
+	bool change;
+	int err;
+
+	mutex_lock(&codec->regmap_lock);
+	if (codec->regmap) {
+		err = regmap_update_bits_check(codec->regmap, reg, mask, val,
+					       &change);
+		if (!err)
+			err = change ? 1 : 0;
+	} else {
+		err = hda_reg_read(codec, reg, &orig);
+		if (!err) {
+			val &= mask;
+			val |= orig & ~mask;
+			if (val != orig) {
+				err = hda_reg_write(codec, reg, val);
+				if (!err)
+					err = 1;
+			}
+		}
+	}
+	mutex_unlock(&codec->regmap_lock);
+	return err;
+}
+
 /**
  * snd_hdac_regmap_update_raw - update a pseudo register with power mgmt
  * @codec: the codec object
@@ -516,19 +550,57 @@ int snd_hdac_regmap_read_raw_uncached(struct hdac_device *codec,
 int snd_hdac_regmap_update_raw(struct hdac_device *codec, unsigned int reg,
 			       unsigned int mask, unsigned int val)
 {
+	return CALL_RAW_FUNC(codec, reg_raw_update(codec, reg, mask, val));
+}
+EXPORT_SYMBOL_GPL(snd_hdac_regmap_update_raw);
+
+static int reg_raw_update_once(struct hdac_device *codec, unsigned int reg,
+			       unsigned int mask, unsigned int val)
+{
 	unsigned int orig;
 	int err;
 
-	val &= mask;
-	err = snd_hdac_regmap_read_raw(codec, reg, &orig);
-	if (err < 0)
-		return err;
-	val |= orig & ~mask;
-	if (val == orig)
-		return 0;
-	err = snd_hdac_regmap_write_raw(codec, reg, val);
+	if (!codec->regmap)
+		return reg_raw_update(codec, reg, mask, val);
+
+	mutex_lock(&codec->regmap_lock);
+	regcache_cache_only(codec->regmap, true);
+	err = regmap_read(codec->regmap, reg, &orig);
+	regcache_cache_only(codec->regmap, false);
 	if (err < 0)
-		return err;
-	return 1;
+		err = regmap_update_bits(codec->regmap, reg, mask, val);
+	mutex_unlock(&codec->regmap_lock);
+	return err;
 }
-EXPORT_SYMBOL_GPL(snd_hdac_regmap_update_raw);
+
+/**
+ * snd_hdac_regmap_update_raw_once - initialize the register value only once
+ * @codec: the codec object
+ * @reg: pseudo register
+ * @mask: bit mask to update
+ * @val: value to update
+ *
+ * Performs the update of the register bits only once when the register
+ * hasn't been initialized yet.  Used in HD-audio legacy driver.
+ * Returns zero if successful or a negative error code
+ */
+int snd_hdac_regmap_update_raw_once(struct hdac_device *codec, unsigned int reg,
+				    unsigned int mask, unsigned int val)
+{
+	return CALL_RAW_FUNC(codec, reg_raw_update_once(codec, reg, mask, val));
+}
+EXPORT_SYMBOL_GPL(snd_hdac_regmap_update_raw_once);
+
+/**
+ * snd_hdac_regmap_sync - sync out the cached values for PM resume
+ * @codec: the codec object
+ */
+void snd_hdac_regmap_sync(struct hdac_device *codec)
+{
+	if (codec->regmap) {
+		mutex_lock(&codec->regmap_lock);
+		regcache_sync(codec->regmap);
+		mutex_unlock(&codec->regmap_lock);
+	}
+}
+EXPORT_SYMBOL_GPL(snd_hdac_regmap_sync);