[PATCH] I2C: Fix OMAP I2C status register handling in IRQ processing

[Seth Forshee <seth.forshee@gmail.com>]

The IRQ handler in omap-i2c.c can sometimes clear status bits without
actually processing them.  In particular, error status bits will be
ignored if any of the ARDY, RRDY, RDR, XRDY, or XDR bits are
concurrently set.

Signed-off-by: Seth Forshee <seth.forshee@gmail.com>
---

More information:

I originally noticed this problem on a custom 2430 board I am working
with.  Whenever an i2c chip driver calls i2c_probe() the device would
be found on both i2c busses at each of the possible addresses for the
device.  I discovered that NACK was being set in the status register
but omap_i2c_xfer() still returned success because ARDY was also set.

This patch fixes this issue on my board and hasn't caused any problems
(in my admittedly light i2c usage).  I don't have immediate access to
an SDP board however, so it has not been tested on that platform.

 drivers/i2c/busses/i2c-omap.c |   28 +++++++++++++---------------
 1 files changed, 13 insertions(+), 15 deletions(-)

diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
index 4777466..a16d513 100644
--- a/drivers/i2c/busses/i2c-omap.c
+++ b/drivers/i2c/busses/i2c-omap.c
@@ -590,7 +590,7 @@ omap_i2c_isr(int this_irq, void *dev_id)
 	struct omap_i2c_dev *dev = dev_id;
 	u16 bits;
 	u16 stat, w;
-	int count = 0;
+	int err, count = 0;
 
 	if (dev->idle)
 		return IRQ_NONE;
@@ -605,10 +605,19 @@ omap_i2c_isr(int this_irq, void *dev_id)
 
 		omap_i2c_write_reg(dev, OMAP_I2C_STAT_REG, stat);
 
-		if (stat & OMAP_I2C_STAT_ARDY) {
-			omap_i2c_complete_cmd(dev, 0);
-			continue;
+		err = 0;
+		if (stat & OMAP_I2C_STAT_NACK) {
+			err |= OMAP_I2C_STAT_NACK;
+			omap_i2c_write_reg(dev, OMAP_I2C_CON_REG,
+					   OMAP_I2C_CON_STP);
 		}
+		if (stat & OMAP_I2C_STAT_AL) {
+			dev_err(dev->dev, "Arbitration lost\n");
+			err |= OMAP_I2C_STAT_AL;
+		}
+		if (stat & (OMAP_I2C_STAT_ARDY | OMAP_I2C_STAT_NACK |
+					OMAP_I2C_STAT_AL))
+			omap_i2c_complete_cmd(dev, err);
 		if (stat & (OMAP_I2C_STAT_RRDY | OMAP_I2C_STAT_RDR)) {
 			u8 num_bytes = 1;
 			if (dev->fifo_size) {
@@ -640,7 +649,6 @@ omap_i2c_isr(int this_irq, void *dev_id)
 				}
 			}
 			omap_i2c_ack_stat(dev, stat & (OMAP_I2C_STAT_RRDY | OMAP_I2C_STAT_RDR));
-			continue;
 		}
 		if (stat & (OMAP_I2C_STAT_XRDY | OMAP_I2C_STAT_XDR)) {
 			u8 num_bytes = 1;
@@ -674,7 +682,6 @@ omap_i2c_isr(int this_irq, void *dev_id)
 				omap_i2c_write_reg(dev, OMAP_I2C_DATA_REG, w);
 			}
 			omap_i2c_ack_stat(dev, stat & (OMAP_I2C_STAT_XRDY | OMAP_I2C_STAT_XDR));
-			continue;
 		}
 		if (stat & OMAP_I2C_STAT_ROVR) {
 			dev_err(dev->dev, "Receive overrun\n");
@@ -684,15 +691,6 @@ omap_i2c_isr(int this_irq, void *dev_id)
 			dev_err(dev->dev, "Transmit overflow\n");
 			dev->cmd_err |= OMAP_I2C_STAT_XUDF;
 		}
-		if (stat & OMAP_I2C_STAT_NACK) {
-			omap_i2c_complete_cmd(dev, OMAP_I2C_STAT_NACK);
-			omap_i2c_write_reg(dev, OMAP_I2C_CON_REG,
-					   OMAP_I2C_CON_STP);
-		}
-		if (stat & OMAP_I2C_STAT_AL) {
-			dev_err(dev->dev, "Arbitration lost\n");
-			omap_i2c_complete_cmd(dev, OMAP_I2C_STAT_AL);
-		}
 	}
 
 	return count ? IRQ_HANDLED : IRQ_NONE;
-- 
1.5.2.5