i2c: xlp9xx: Check for Bus state before every transfer

BugLink: https://bugs.launchpad.net/bugs/1762812
I2C bus enters the STOP condition after the DATA_DONE interrupt is raised.
Essentially the driver should be checking the bus state before sending
any transaction. In case a transaction is initiated while the
bus is busy, the prior transaction's stop condition is not achieved.
Add the check to make sure the bus is not busy before every transaction.

Signed-off-by: George Cherian <george.cherian@cavium.com>
Reviewed-by: Jan Glauber <jglauber@cavium.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
(cherry picked from commit d3898a78521cd383d287b3ed5683f914c48c3be9)
Signed-off-by: dann frazier <dann.frazier@canonical.com>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>

diff --git a/drivers/i2c/busses/i2c-xlp9xx.c b/drivers/i2c/busses/i2c-xlp9xx.c
index 1f6d78087af9d742514f852fa30b7acba4c45cb5..42dd1fa0b6442550577fbeca13c4c0ea220896ba 100644 (file)
--- a/drivers/i2c/busses/i2c-xlp9xx.c
+++ b/drivers/i2c/busses/i2c-xlp9xx.c
@@ -16,6 +16,7 @@
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/platform_device.h>
+#include <linux/delay.h>
 
 #define XLP9XX_I2C_DIV                 0x0
 #define XLP9XX_I2C_CTRL                        0x1
@@ -36,6 +37,8 @@
 #define XLP9XX_I2C_TIMEOUT             0X10
 #define XLP9XX_I2C_GENCALLADDR         0x11
 
+#define XLP9XX_I2C_STATUS_BUSY         BIT(0)
+
 #define XLP9XX_I2C_CMD_START           BIT(7)
 #define XLP9XX_I2C_CMD_STOP            BIT(6)
 #define XLP9XX_I2C_CMD_READ            BIT(5)
@@ -71,6 +74,7 @@
 #define XLP9XX_I2C_HIGH_FREQ           400000
 #define XLP9XX_I2C_FIFO_SIZE           0x80U
 #define XLP9XX_I2C_TIMEOUT_MS          1000
+#define XLP9XX_I2C_BUSY_TIMEOUT                50
 
 #define XLP9XX_I2C_FIFO_WCNT_MASK      0xff
 #define XLP9XX_I2C_STATUS_ERRMASK      (XLP9XX_I2C_INTEN_ARLOST | \
@@ -241,6 +245,26 @@ xfer_done:
        return IRQ_HANDLED;
 }
 
+static int xlp9xx_i2c_check_bus_status(struct xlp9xx_i2c_dev *priv)
+{
+       u32 status;
+       u32 busy_timeout = XLP9XX_I2C_BUSY_TIMEOUT;
+
+       while (busy_timeout) {
+               status = xlp9xx_read_i2c_reg(priv, XLP9XX_I2C_STATUS);
+               if ((status & XLP9XX_I2C_STATUS_BUSY) == 0)
+                       break;
+
+               busy_timeout--;
+               usleep_range(1000, 1100);
+       }
+
+       if (!busy_timeout)
+               return -EIO;
+
+       return 0;
+}
+
 static int xlp9xx_i2c_init(struct xlp9xx_i2c_dev *priv)
 {
        u32 prescale;
@@ -363,6 +387,14 @@ static int xlp9xx_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
        int i, ret;
        struct xlp9xx_i2c_dev *priv = i2c_get_adapdata(adap);
 
+       ret = xlp9xx_i2c_check_bus_status(priv);
+       if (ret) {
+               xlp9xx_i2c_init(priv);
+               ret = xlp9xx_i2c_check_bus_status(priv);
+               if (ret)
+                       return ret;
+       }
+
        for (i = 0; i < num; i++) {
                ret = xlp9xx_i2c_xfer_msg(priv, &msgs[i], i == num - 1);
                if (ret != 0)