[ALSA] at73c213: replace spinlock in mixer functions with a mutex

This patch fixes the locking bug in the at73c213 SPI sound driver. This bug was
triggered because spinlocks were wrapped around the spi_sync call which might
sleep. The fix was to add a mutex to the sound driver and replace the spinlocks
in the mixer functions with mutex lock/unlock.
Tested on STK1000/STK1002.

Signed-off-by: Hans-Christian Egtvedt <hcegtvedt@atmel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

1 files changed, 19 insertions, 15 deletions

diff --git a/sound/spi/at73c213.c b/sound/spi/at73c213.c
index bfe17b3ec8f4..5e8cf9f44ca3 100644
--- a/sound/spi/at73c213.c
+++ b/sound/spi/at73c213.c
@@ -18,6 +18,7 @@
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/module.h>
+#include <linux/mutex.h>
 #include <linux/platform_device.h>
 #include <linux/io.h>
 
@@ -76,8 +77,10 @@ struct snd_at73c213 {
         u8                              spi_rbuffer[2];
         /* Image of the SPI registers in AT73C213. */
         u8                              reg_image[18];
-        /* Protect registers against concurrent access. */
+        /* Protect SSC registers against concurrent access. */
         spinlock_t                      lock;
+        /* Protect mixer registers against concurrent access. */
+        struct mutex                    mixer_lock;
 };
 
 #define get_chip(card) ((struct snd_at73c213 *)card->private_data)
@@ -398,7 +401,7 @@ static int snd_at73c213_mono_get(struct snd_kcontrol *kcontrol,
         int mask = (kcontrol->private_value >> 16) & 0xff;
         int invert = (kcontrol->private_value >> 24) & 0xff;
 
-        spin_lock_irq(&chip->lock);
+        mutex_lock(&chip->mixer_lock);
 
         ucontrol->value.integer.value[0] =
                 (chip->reg_image[reg] >> shift) & mask;
@@ -407,7 +410,7 @@ static int snd_at73c213_mono_get(struct snd_kcontrol *kcontrol,
                 ucontrol->value.integer.value[0] =
                         mask - ucontrol->value.integer.value[0];
 
-        spin_unlock_irq(&chip->lock);
+        mutex_unlock(&chip->mixer_lock);
 
         return 0;
 }
@@ -428,13 +431,13 @@ static int snd_at73c213_mono_put(struct snd_kcontrol *kcontrol,
                 val = mask - val;
         val <<= shift;
 
-        spin_lock_irq(&chip->lock);
+        mutex_lock(&chip->mixer_lock);
 
         val = (chip->reg_image[reg] & ~(mask << shift)) | val;
         change = val != chip->reg_image[reg];
         retval = snd_at73c213_write_reg(chip, reg, val);
 
-        spin_unlock_irq(&chip->lock);
+        mutex_unlock(&chip->mixer_lock);
 
         if (retval)
                 return retval;
@@ -470,7 +473,7 @@ static int snd_at73c213_stereo_get(struct snd_kcontrol *kcontrol,
         int mask = (kcontrol->private_value >> 24) & 0xff;
         int invert = (kcontrol->private_value >> 22) & 1;
 
-        spin_lock_irq(&chip->lock);
+        mutex_lock(&chip->mixer_lock);
 
         ucontrol->value.integer.value[0] =
                 (chip->reg_image[left_reg] >> shift_left) & mask;
@@ -484,7 +487,7 @@ static int snd_at73c213_stereo_get(struct snd_kcontrol *kcontrol,
                         mask - ucontrol->value.integer.value[1];
         }
 
-        spin_unlock_irq(&chip->lock);
+        mutex_unlock(&chip->mixer_lock);
 
         return 0;
 }
@@ -511,7 +514,7 @@ static int snd_at73c213_stereo_put(struct snd_kcontrol *kcontrol,
         val1 <<= shift_left;
         val2 <<= shift_right;
 
-        spin_lock_irq(&chip->lock);
+        mutex_lock(&chip->mixer_lock);
 
         val1 = (chip->reg_image[left_reg] & ~(mask << shift_left)) | val1;
         val2 = (chip->reg_image[right_reg] & ~(mask << shift_right)) | val2;
@@ -519,16 +522,16 @@ static int snd_at73c213_stereo_put(struct snd_kcontrol *kcontrol,
                 || val2 != chip->reg_image[right_reg];
         retval = snd_at73c213_write_reg(chip, left_reg, val1);
         if (retval) {
-                spin_unlock_irq(&chip->lock);
+                mutex_unlock(&chip->mixer_lock);
                 goto out;
         }
         retval = snd_at73c213_write_reg(chip, right_reg, val2);
         if (retval) {
-                spin_unlock_irq(&chip->lock);
+                mutex_unlock(&chip->mixer_lock);
                 goto out;
         }
 
-        spin_unlock_irq(&chip->lock);
+        mutex_unlock(&chip->mixer_lock);
 
         return change;
 
@@ -546,7 +549,7 @@ static int snd_at73c213_mono_switch_get(struct snd_kcontrol *kcontrol,
         int shift = (kcontrol->private_value >> 8) & 0xff;
         int invert = (kcontrol->private_value >> 24) & 0xff;
 
-        spin_lock_irq(&chip->lock);
+        mutex_lock(&chip->mixer_lock);
 
         ucontrol->value.integer.value[0] =
                 (chip->reg_image[reg] >> shift) & 0x01;
@@ -555,7 +558,7 @@ static int snd_at73c213_mono_switch_get(struct snd_kcontrol *kcontrol,
                 ucontrol->value.integer.value[0] =
                         0x01 - ucontrol->value.integer.value[0];
 
-        spin_unlock_irq(&chip->lock);
+        mutex_unlock(&chip->mixer_lock);
 
         return 0;
 }
@@ -580,14 +583,14 @@ static int snd_at73c213_mono_switch_put(struct snd_kcontrol *kcontrol,
                 val = mask - val;
         val <<= shift;
 
-        spin_lock_irq(&chip->lock);
+        mutex_lock(&chip->mixer_lock);
 
         val |= (chip->reg_image[reg] & ~(mask << shift));
         change = val != chip->reg_image[reg];
 
         retval = snd_at73c213_write_reg(chip, reg, val);
 
-        spin_unlock_irq(&chip->lock);
+        mutex_unlock(&chip->mixer_lock);
 
         if (retval)
                 return retval;
@@ -884,6 +887,7 @@ static int __devinit snd_at73c213_dev_init(struct snd_card *card,
                 return irq;
 
         spin_lock_init(&chip->lock);
+        mutex_init(&chip->mixer_lock);
         chip->card = card;
         chip->irq = -1;