rt2x00: Fix race condition when using inderect registers

Indirect registers require multiple calls to the CSR
register in order to access the indirect registers.
This must be protected under a lock to prevent race
conditions which could cause invalid data to
be returned when reading from the indirect register or silent
failures when writing data to the indirect register.

USB drivers where already protected under a mutex,
so rename the mutex and make PCI drivers use the mutex
as well.
This now means that BBP and RF registers are no longer
accessible in interrupt context. That is not a bad
situation since the slow behavior of accessing
those registers means we don't _want_ to access them
in interrupt context either.

Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 34 insertions, 13 deletions

diff --git a/drivers/net/wireless/rt2x00/rt2400pci.c b/drivers/net/wireless/rt2x00/rt2400pci.c
index 9bda3889539c..78fca1bcc544 100644
--- a/drivers/net/wireless/rt2x00/rt2400pci.c
+++ b/drivers/net/wireless/rt2x00/rt2400pci.c
@@ -69,14 +69,14 @@ static void rt2400pci_bbp_write(struct rt2x00_dev *rt2x00dev,
 {
         u32 reg;
 
+        mutex_lock(&rt2x00dev->csr_mutex);
+
         /*
          * Wait until the BBP becomes ready.
          */
         reg = rt2400pci_bbp_check(rt2x00dev);
-        if (rt2x00_get_field32(reg, BBPCSR_BUSY)) {
-                ERROR(rt2x00dev, "BBPCSR register busy. Write failed.\n");
-                return;
-        }
+        if (rt2x00_get_field32(reg, BBPCSR_BUSY))
+                goto exit_fail;
 
         /*
          * Write the data into the BBP.
@@ -88,6 +88,15 @@ static void rt2400pci_bbp_write(struct rt2x00_dev *rt2x00dev,
         rt2x00_set_field32(&reg, BBPCSR_WRITE_CONTROL, 1);
 
         rt2x00pci_register_write(rt2x00dev, BBPCSR, reg);
+
+        mutex_unlock(&rt2x00dev->csr_mutex);
+
+        return;
+
+exit_fail:
+        mutex_unlock(&rt2x00dev->csr_mutex);
+
+        ERROR(rt2x00dev, "BBPCSR register busy. Write failed.\n");
 }
 
 static void rt2400pci_bbp_read(struct rt2x00_dev *rt2x00dev,
@@ -95,14 +104,14 @@ static void rt2400pci_bbp_read(struct rt2x00_dev *rt2x00dev,
 {
         u32 reg;
 
+        mutex_lock(&rt2x00dev->csr_mutex);
+
         /*
          * Wait until the BBP becomes ready.
          */
         reg = rt2400pci_bbp_check(rt2x00dev);
-        if (rt2x00_get_field32(reg, BBPCSR_BUSY)) {
-                ERROR(rt2x00dev, "BBPCSR register busy. Read failed.\n");
-                return;
-        }
+        if (rt2x00_get_field32(reg, BBPCSR_BUSY))
+                goto exit_fail;
 
         /*
          * Write the request into the BBP.
@@ -118,13 +127,20 @@ static void rt2400pci_bbp_read(struct rt2x00_dev *rt2x00dev,
          * Wait until the BBP becomes ready.
          */
         reg = rt2400pci_bbp_check(rt2x00dev);
-        if (rt2x00_get_field32(reg, BBPCSR_BUSY)) {
-                ERROR(rt2x00dev, "BBPCSR register busy. Read failed.\n");
-                *value = 0xff;
-                return;
-        }
+        if (rt2x00_get_field32(reg, BBPCSR_BUSY))
+                goto exit_fail;
 
         *value = rt2x00_get_field32(reg, BBPCSR_VALUE);
+
+        mutex_unlock(&rt2x00dev->csr_mutex);
+
+        return;
+
+exit_fail:
+        mutex_unlock(&rt2x00dev->csr_mutex);
+
+        ERROR(rt2x00dev, "BBPCSR register busy. Read failed.\n");
+        *value = 0xff;
 }
 
 static void rt2400pci_rf_write(struct rt2x00_dev *rt2x00dev,
@@ -136,6 +152,8 @@ static void rt2400pci_rf_write(struct rt2x00_dev *rt2x00dev,
         if (!word)
                 return;
 
+        mutex_lock(&rt2x00dev->csr_mutex);
+
         for (i = 0; i < REGISTER_BUSY_COUNT; i++) {
                 rt2x00pci_register_read(rt2x00dev, RFCSR, &reg);
                 if (!rt2x00_get_field32(reg, RFCSR_BUSY))
@@ -143,6 +161,7 @@ static void rt2400pci_rf_write(struct rt2x00_dev *rt2x00dev,
                 udelay(REGISTER_BUSY_DELAY);
         }
 
+        mutex_unlock(&rt2x00dev->csr_mutex);
         ERROR(rt2x00dev, "RFCSR register busy. Write failed.\n");
         return;
 
@@ -155,6 +174,8 @@ rf_write:
 
         rt2x00pci_register_write(rt2x00dev, RFCSR, reg);
         rt2x00_rf_write(rt2x00dev, word, value);
+
+        mutex_unlock(&rt2x00dev->csr_mutex);
 }
 
 static void rt2400pci_eepromregister_read(struct eeprom_93cx6 *eeprom)