V4L/DVB (6857): cx23885: correctly join I2C writes and reads from same address

When an I2C message specifies a write then a read from the same I2C address,
we need to tell the chip to not release the bus between the message parts.

Signed-off-by: Chris Pascoe <c.pascoe@itee.uq.edu.au>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>

1 files changed, 39 insertions, 14 deletions

diff --git a/drivers/media/video/cx23885/cx23885-i2c.c b/drivers/media/video/cx23885/cx23885-i2c.c
index 08e92df33168..20f3fb450f88 100644
--- a/drivers/media/video/cx23885/cx23885-i2c.c
+++ b/drivers/media/video/cx23885/cx23885-i2c.c
@@ -37,8 +37,10 @@ static unsigned int i2c_scan = 0;
 module_param(i2c_scan, int, 0444);
 MODULE_PARM_DESC(i2c_scan, "scan i2c bus at insmod time");
 
-#define dprintk(level,fmt, arg...)      if (i2c_debug >= level) \
-        printk(KERN_DEBUG "%s: " fmt, dev->name , ## arg)
+#define dprintk(level, fmt, arg...)     do { \
+        if (i2c_debug >= level) \
+                printk(KERN_DEBUG "%s: " fmt, dev->name , ## arg); \
+        } while (0)
 
 #define I2C_WAIT_DELAY 32
 #define I2C_WAIT_RETRY 64
@@ -77,14 +79,18 @@ static int i2c_wait_done(struct i2c_adapter *i2c_adap)
 }
 
 static int i2c_sendbytes(struct i2c_adapter *i2c_adap,
-                         const struct i2c_msg *msg, int last)
+                         const struct i2c_msg *msg, int joined_rlen)
 {
         struct cx23885_i2c *bus = i2c_adap->algo_data;
         struct cx23885_dev *dev = bus->dev;
         u32 wdata, addr, ctrl;
         int retval, cnt;
 
-        dprintk(1, "%s(msg->len=%d, last=%d)\n", __FUNCTION__, msg->len, last);
+        if (joined_rlen)
+                dprintk(1, "%s(msg->wlen=%d, nextmsg->rlen=%d)\n", __FUNCTION__,
+                        msg->len, joined_rlen);
+        else
+                dprintk(1, "%s(msg->len=%d)\n", __FUNCTION__, msg->len);
 
         /* Deal with i2c probe functions with zero payload */
         if (msg->len == 0) {
@@ -107,6 +113,8 @@ static int i2c_sendbytes(struct i2c_adapter *i2c_adap,
 
         if (msg->len > 1)
                 ctrl |= I2C_NOSTOP | I2C_EXTEND;
+        else if (joined_rlen)
+                ctrl |= I2C_NOSTOP;
 
         cx_write(bus->reg_addr, addr);
         cx_write(bus->reg_wdata, wdata);
@@ -130,6 +138,8 @@ static int i2c_sendbytes(struct i2c_adapter *i2c_adap,
 
                 if (cnt < msg->len - 1)
                         ctrl |= I2C_NOSTOP | I2C_EXTEND;
+                else if (joined_rlen)
+                        ctrl |= I2C_NOSTOP;
 
                 cx_write(bus->reg_addr, addr);
                 cx_write(bus->reg_wdata, wdata);
@@ -151,19 +161,22 @@ static int i2c_sendbytes(struct i2c_adapter *i2c_adap,
  eio:
         retval = -EIO;
  err:
-        printk(" ERR: %d\n", retval);
+        if (i2c_debug)
+                printk(" ERR: %d\n", retval);
         return retval;
 }
 
 static int i2c_readbytes(struct i2c_adapter *i2c_adap,
-                         const struct i2c_msg *msg, int last)
+                         const struct i2c_msg *msg, int joined)
 {
         struct cx23885_i2c *bus = i2c_adap->algo_data;
         struct cx23885_dev *dev = bus->dev;
         u32 ctrl, cnt;
         int retval;
 
-        dprintk(1, "%s(msg->len=%d, last=%d)\n", __FUNCTION__, msg->len, last);
+
+        if (i2c_debug && !joined)
+                dprintk(1, "%s(msg->len=%d)\n", __FUNCTION__, msg->len);
 
         /* Deal with i2c probe functions with zero payload */
         if (msg->len == 0) {
@@ -179,8 +192,12 @@ static int i2c_readbytes(struct i2c_adapter *i2c_adap,
                 return 0;
         }
 
-        if (i2c_debug)
-                printk(" <R %02x", (msg->addr << 1) + 1);
+        if (i2c_debug) {
+                if (joined)
+                        printk(" R");
+                else
+                        printk(" <R %02x", (msg->addr << 1) + 1);
+        }
 
         for(cnt = 0; cnt < msg->len; cnt++) {
 
@@ -209,7 +226,8 @@ static int i2c_readbytes(struct i2c_adapter *i2c_adap,
  eio:
         retval = -EIO;
  err:
-        printk(" ERR: %d\n", retval);
+        if (i2c_debug)
+                printk(" ERR: %d\n", retval);
         return retval;
 }
 
@@ -227,15 +245,22 @@ static int i2c_xfer(struct i2c_adapter *i2c_adap,
                         __FUNCTION__, num, msgs[i].addr, msgs[i].len);
                 if (msgs[i].flags & I2C_M_RD) {
                         /* read */
-                        retval = i2c_readbytes(i2c_adap, &msgs[i], i+1 == num);
+                        retval = i2c_readbytes(i2c_adap, &msgs[i], 0);
+                } else if (i + 1 < num && (msgs[i + 1].flags & I2C_M_RD) &&
+                           msgs[i].addr == msgs[i + 1].addr) {
+                        /* write then read from same address */
+                        retval = i2c_sendbytes(i2c_adap, &msgs[i],
+                                               msgs[i + 1].len);
                         if (retval < 0)
                                 goto err;
+                        i++;
+                        retval = i2c_readbytes(i2c_adap, &msgs[i], 1);
                 } else {
                         /* write */
-                        retval = i2c_sendbytes(i2c_adap, &msgs[i], i+1 == num);
-                        if (retval < 0)
-                                goto err;
+                        retval = i2c_sendbytes(i2c_adap, &msgs[i], 0);
                 }
+                if (retval < 0)
+                        goto err;
         }
         return num;