ASoC: add locking to mpc5200-psc-ac97 driver

AC97 bus register read/write hooks need to provide locking, but the
mpc5200-psc-ac97 driver does not.  This patch adds a mutex around
the register access routines.
Signed-off-by: Grant Likely <grant.likely@secretlab.ca>
Acked-by: Jon Smirl <jonsmirl@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/fsl/mpc5200_dma.c

@@ -456,6 +456,7 @@ int mpc5200_audio_dma_create(struct of_device *op)
 		return -ENODEV;
 
 	spin_lock_init(&psc_dma->lock);
+	mutex_init(&psc_dma->mutex);
 	psc_dma->id = be32_to_cpu(*prop);
 	psc_dma->irq = irq;
 	psc_dma->psc_regs = regs;

sound/soc/fsl/mpc5200_dma.h

@@ -55,6 +55,7 @@ struct psc_dma {
 	unsigned int irq;
 	struct device *dev;
 	spinlock_t lock;
+	struct mutex mutex;
 	u32 sicr;
 	uint sysclk;
 	int imr;

sound/soc/fsl/mpc5200_psc_ac97.c

@@ -34,11 +34,14 @@ static unsigned short psc_ac97_read(struct snd_ac97 *ac97, unsigned short reg)
 	int status;
 	unsigned int val;
 
+	mutex_lock(&psc_dma->mutex);
+
 	/* Wait for command send status zero = ready */
 	status = spin_event_timeout(!(in_be16(&psc_dma->psc_regs->sr_csr.status) &
 				MPC52xx_PSC_SR_CMDSEND), 100, 0);
 	if (status == 0) {
 		pr_err("timeout on ac97 bus (rdy)\n");
+		mutex_unlock(&psc_dma->mutex);
 		return -ENODEV;
 	}
 
@@ -54,16 +57,19 @@ static unsigned short psc_ac97_read(struct snd_ac97 *ac97, unsigned short reg)
 	if (status == 0) {
 		pr_err("timeout on ac97 read (val) %x\n",
 				in_be16(&psc_dma->psc_regs->sr_csr.status));
+		mutex_unlock(&psc_dma->mutex);
 		return -ENODEV;
 	}
 	/* Get the data */
 	val = in_be32(&psc_dma->psc_regs->ac97_data);
 	if (((val >> 24) & 0x7f) != reg) {
 		pr_err("reg echo error on ac97 read\n");
+		mutex_unlock(&psc_dma->mutex);
 		return -ENODEV;
 	}
 	val = (val >> 8) & 0xffff;
 
+	mutex_unlock(&psc_dma->mutex);
 	return (unsigned short) val;
 }
 
@@ -72,16 +78,21 @@ static void psc_ac97_write(struct snd_ac97 *ac97,
 {
 	int status;
 
+	mutex_lock(&psc_dma->mutex);
+
 	/* Wait for command status zero = ready */
 	status = spin_event_timeout(!(in_be16(&psc_dma->psc_regs->sr_csr.status) &
 				MPC52xx_PSC_SR_CMDSEND), 100, 0);
 	if (status == 0) {
 		pr_err("timeout on ac97 bus (write)\n");
-		return;
+		goto out;
 	}
 	/* Write data */
 	out_be32(&psc_dma->psc_regs->ac97_cmd,
 			((reg & 0x7f) << 24) | (val << 8));
+
+ out:
+	mutex_unlock(&psc_dma->mutex);
 }
 
 static void psc_ac97_warm_reset(struct snd_ac97 *ac97)