[ARM] 4140/1: AACI stability add ac97 timeout and retries

Add timeouts to hardware read/write/probe functions in order
to avoid lockups on buggy/broken hardware.

Signed-off-by: Kevin Hilman <khilman@mvista.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --git a/sound/arm/aaci.c b/sound/arm/aaci.c
index a032aee82adf152b34e97cc9a61406dcb7eaea1c..5190d7acdb9fd6306761c8a7da2a689d561e1f0c 100644 (file)
--- a/sound/arm/aaci.c
+++ b/sound/arm/aaci.c
@@ -65,10 +65,12 @@ static void aaci_ac97_select_codec(struct aaci *aaci, struct snd_ac97 *ac97)
  *  SI1TxEn, SI2TxEn and SI12TxEn bits are set in the AACI_MAINCR
  *  register.
  */
-static void aaci_ac97_write(struct snd_ac97 *ac97, unsigned short reg, unsigned short val)
+static void aaci_ac97_write(struct snd_ac97 *ac97, unsigned short reg,
+                           unsigned short val)
 {
        struct aaci *aaci = ac97->private_data;
        u32 v;
+       int timeout = 5000;
 
        if (ac97->num >= 4)
                return;
@@ -89,7 +91,11 @@ static void aaci_ac97_write(struct snd_ac97 *ac97, unsigned short reg, unsigned
         */
        do {
                v = readl(aaci->base + AACI_SLFR);
-       } while (v & (SLFR_1TXB|SLFR_2TXB));
+       } while ((v & (SLFR_1TXB|SLFR_2TXB)) && timeout--);
+
+       if (!timeout)
+               dev_err(&aaci->dev->dev,
+                       "timeout waiting for write to complete\n");
 
        mutex_unlock(&aaci->ac97_sem);
 }
@@ -101,6 +107,8 @@ static unsigned short aaci_ac97_read(struct snd_ac97 *ac97, unsigned short reg)
 {
        struct aaci *aaci = ac97->private_data;
        u32 v;
+       int timeout = 5000;
+       int retries = 10;
 
        if (ac97->num >= 4)
                return ~0;
@@ -119,7 +127,13 @@ static unsigned short aaci_ac97_read(struct snd_ac97 *ac97, unsigned short reg)
         */
        do {
                v = readl(aaci->base + AACI_SLFR);
-       } while (v & SLFR_1TXB);
+       } while ((v & SLFR_1TXB) && timeout--);
+
+       if (!timeout) {
+               dev_err(&aaci->dev->dev, "timeout on slot 1 TX busy\n");
+               v = ~0;
+               goto out;
+       }
 
        /*
         * Give the AC'97 codec more than enough time
@@ -130,21 +144,35 @@ static unsigned short aaci_ac97_read(struct snd_ac97 *ac97, unsigned short reg)
        /*
         * Wait for slot 2 to indicate data.
         */
+       timeout = 5000;
        do {
                cond_resched();
                v = readl(aaci->base + AACI_SLFR) & (SLFR_1RXV|SLFR_2RXV);
-       } while (v != (SLFR_1RXV|SLFR_2RXV));
+       } while ((v != (SLFR_1RXV|SLFR_2RXV)) && timeout--);
 
-       v = readl(aaci->base + AACI_SL1RX) >> 12;
-       if (v == reg) {
-               v = readl(aaci->base + AACI_SL2RX) >> 4;
-       } else {
-               dev_err(&aaci->dev->dev,
-                       "wrong ac97 register read back (%x != %x)\n",
-                       v, reg);
+       if (!timeout) {
+               dev_err(&aaci->dev->dev, "timeout on RX valid\n");
                v = ~0;
+               goto out;
        }
 
+       do {
+               v = readl(aaci->base + AACI_SL1RX) >> 12;
+               if (v == reg) {
+                       v = readl(aaci->base + AACI_SL2RX) >> 4;
+                       break;
+               } else if (--retries) {
+                       dev_warn(&aaci->dev->dev,
+                                "ac97 read back fail.  retry\n");
+                       continue;
+               } else {
+                       dev_warn(&aaci->dev->dev,
+                               "wrong ac97 register read back (%x != %x)\n",
+                               v, reg);
+                       v = ~0;
+               }
+       } while (retries);
+ out:
        mutex_unlock(&aaci->ac97_sem);
        return v;
 }