mpfs_i2c: fix semaphore race condition

MPFS_I2C_ST_STOP_SENT interrupt might be received right after semaphore timeout, which would cause the semaphore to be in the incorrect signaled state when the next transfer starts. Signed-off-by: Tero Salminen <[email protected]>
tiiuae · Mar 25, 2024 · d1140a5 · d1140a5
1 parent 8b2053d
commit d1140a5
Showing 1 changed file with 23 additions and 3 deletions.
diff --git a/arch/risc-v/src/mpfs/mpfs_i2c.c b/arch/risc-v/src/mpfs/mpfs_i2c.c
@@ -425,6 +425,10 @@ static int mpfs_i2c_init(struct mpfs_i2c_priv_s *priv)
 
       putreg32(MPFS_I2C_CTRL_ENS1_MASK, MPFS_I2C_CTRL);
 
+#ifdef CONFIG_MPFS_COREI2C
+      nxsem_init(&priv->sem_isr, 0, 0);
+#endif
+
       priv->initialized = true;
     }
 
@@ -469,8 +473,24 @@ static void mpfs_i2c_deinit(struct mpfs_i2c_priv_s *priv)
 
 static int mpfs_i2c_sem_waitdone(struct mpfs_i2c_priv_s *priv)
 {
+  int res = 0;
   uint32_t timeout = mpfs_i2c_timeout(priv->msgc, priv->msgv);
-  return nxsem_tickwait_uninterruptible(&priv->sem_isr, USEC2TICK(timeout));
+
+  res = nxsem_tickwait_uninterruptible(&priv->sem_isr, USEC2TICK(timeout));
+
+  /* -> race condition <- */
+
+  priv->inflight = false;
+
+  /* Handle a race condition above in which interrupt MPFS_I2C_ST_STOP_SENT was
+   * received right after semaphore timeout. In that case semaphore is signalled
+   * and has the incorrect state when the next transfer starts.
+   */
+  if (res < 0) {
+    res = nxsem_tickwait_uninterruptible(&priv->sem_isr, USEC2TICK(timeout));
+  }
+
+  return res;
 }
 
 /****************************************************************************
@@ -872,7 +892,6 @@ static int mpfs_i2c_transfer(struct i2c_master_s *dev,
       if (mpfs_i2c_sem_waitdone(priv) < 0)
         {
           i2cinfo("Message %" PRIu8 " timed out.\n", priv->msgid);
-          priv->inflight = false;
           ret = -ETIMEDOUT;
           break;
         }
@@ -933,6 +952,8 @@ static int mpfs_i2c_reset(struct i2c_master_s *dev)
 
   nxmutex_lock(&priv->lock);
 
+  i2cerr("i2c bus %d reset\n", priv->id);
+
   mpfs_i2c_deinit(priv);
 
   ret = mpfs_i2c_init(priv);
@@ -1138,7 +1159,6 @@ struct i2c_master_s *mpfs_i2cbus_initialize(int port)
   priv->hw_base = CONFIG_MPFS_COREI2C_BASE +
     port * CONFIG_MPFS_COREI2C_INST_OFFSET;
   priv->plic_irq = MPFS_IRQ_FABRIC_F2H_0 + CONFIG_MPFS_COREI2C_IRQNUM + port;
-  nxsem_init(&priv->sem_isr, 0, 0);
   priv->status = MPFS_I2C_SUCCESS;
   priv->fpga = true;
 #endif