[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>

1 files changed, 39 insertions, 11 deletions

diff --git a/sound/arm/aaci.c b/sound/arm/aaci.c
index a032aee82adf..5190d7acdb9f 100644
--- 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;
 }