i2c-davinci: Fix signal handling bug

If wait_for_completion_interruptible_timeout exits due
to a signal, the i2c bus was locking up.

Signed-off-by: Troy Kisky <troy.kisky@boundarydevices.com>
Signed-off-by: Kevin Hilman <khilman@mvista.com>
Signed-off-by: Jean Delvare <khali@linux-fr.org>

1 files changed, 52 insertions, 10 deletions

diff --git a/drivers/i2c/busses/i2c-davinci.c b/drivers/i2c/busses/i2c-davinci.c
index c56f8fe4efe5..160857296952 100644
--- a/drivers/i2c/busses/i2c-davinci.c
+++ b/drivers/i2c/busses/i2c-davinci.c
@@ -85,6 +85,7 @@
 #define DAVINCI_I2C_MDR_MST     (1 << 10)
 #define DAVINCI_I2C_MDR_TRX     (1 << 9)
 #define DAVINCI_I2C_MDR_XA      (1 << 8)
+#define DAVINCI_I2C_MDR_RM      (1 << 7)
 #define DAVINCI_I2C_MDR_IRS     (1 << 5)
 
 #define DAVINCI_I2C_IMR_AAS     (1 << 6)
@@ -112,6 +113,7 @@ struct davinci_i2c_dev {
         u8                      *buf;
         size_t                  buf_len;
         int                     irq;
+        u8                      terminate;
         struct i2c_adapter      adapter;
 };
 
@@ -283,20 +285,34 @@ i2c_davinci_xfer_msg(struct i2c_adapter *adap, struct i2c_msg *msg, int stop)
                 MOD_REG_BIT(w, DAVINCI_I2C_IMR_XRDY, 1);
         davinci_i2c_write_reg(dev, DAVINCI_I2C_IMR_REG, w);
 
+        dev->terminate = 0;
         /* write the data into mode register */
         davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, flag);
 
         r = wait_for_completion_interruptible_timeout(&dev->cmd_complete,
                                                       DAVINCI_I2C_TIMEOUT);
-        dev->buf_len = 0;
-        if (r < 0)
-                return r;
-
         if (r == 0) {
                 dev_err(dev->dev, "controller timed out\n");
                 i2c_davinci_init(dev);
+                dev->buf_len = 0;
                 return -ETIMEDOUT;
         }
+        if (dev->buf_len) {
+                /* This should be 0 if all bytes were transferred
+                 * or dev->cmd_err denotes an error.
+                 * A signal may have aborted the transfer.
+                 */
+                if (r >= 0) {
+                        dev_err(dev->dev, "abnormal termination buf_len=%i\n",
+                                dev->buf_len);
+                        r = -EREMOTEIO;
+                }
+                dev->terminate = 1;
+                wmb();
+                dev->buf_len = 0;
+        }
+        if (r < 0)
+                return r;
 
         /* no error */
         if (likely(!dev->cmd_err))
@@ -354,6 +370,27 @@ static u32 i2c_davinci_func(struct i2c_adapter *adap)
         return I2C_FUNC_I2C | (I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK);
 }
 
+static void terminate_read(struct davinci_i2c_dev *dev)
+{
+        u16 w = davinci_i2c_read_reg(dev, DAVINCI_I2C_MDR_REG);
+        w |= DAVINCI_I2C_MDR_NACK;
+        davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, w);
+
+        /* Throw away data */
+        davinci_i2c_read_reg(dev, DAVINCI_I2C_DRR_REG);
+        if (!dev->terminate)
+                dev_err(dev->dev, "RDR IRQ while no data requested\n");
+}
+static void terminate_write(struct davinci_i2c_dev *dev)
+{
+        u16 w = davinci_i2c_read_reg(dev, DAVINCI_I2C_MDR_REG);
+        w |= DAVINCI_I2C_MDR_RM | DAVINCI_I2C_MDR_STP;
+        davinci_i2c_write_reg(dev, DAVINCI_I2C_MDR_REG, w);
+
+        if (!dev->terminate)
+                dev_err(dev->dev, "TDR IRQ while no data to send\n");
+}
+
 /*
  * Interrupt service routine. This gets called whenever an I2C interrupt
  * occurs.
@@ -374,12 +411,15 @@ static irqreturn_t i2c_davinci_isr(int this_irq, void *dev_id)
 
                 switch (stat) {
                 case DAVINCI_I2C_IVR_AL:
+                        /* Arbitration lost, must retry */
                         dev->cmd_err |= DAVINCI_I2C_STR_AL;
+                        dev->buf_len = 0;
                         complete(&dev->cmd_complete);
                         break;
 
                 case DAVINCI_I2C_IVR_NACK:
                         dev->cmd_err |= DAVINCI_I2C_STR_NACK;
+                        dev->buf_len = 0;
                         complete(&dev->cmd_complete);
                         break;
 
@@ -401,9 +441,10 @@ static irqreturn_t i2c_davinci_isr(int this_irq, void *dev_id)
                                 davinci_i2c_write_reg(dev,
                                         DAVINCI_I2C_STR_REG,
                                         DAVINCI_I2C_IMR_RRDY);
-                        } else
-                                dev_err(dev->dev, "RDR IRQ while no "
-                                        "data requested\n");
+                        } else {
+                                /* signal can terminate transfer */
+                                terminate_read(dev);
+                        }
                         break;
 
                 case DAVINCI_I2C_IVR_XRDY:
@@ -420,9 +461,10 @@ static irqreturn_t i2c_davinci_isr(int this_irq, void *dev_id)
                                 davinci_i2c_write_reg(dev,
                                                       DAVINCI_I2C_IMR_REG,
                                                       w);
-                        } else
-                                dev_err(dev->dev, "TDR IRQ while no data to "
-                                        "send\n");
+                        } else {
+                                /* signal can terminate transfer */
+                                terminate_write(dev);
+                        }
                         break;
 
                 case DAVINCI_I2C_IVR_SCD: