i2c: omap: add notes related to i2c multimaster mode

No functional changes.

Signed-off-by: Alexander Kochetkov <al.kochet@gmail.com>
Reviewed-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
index b70270d..9f5b57a 100644 (file)
--- a/drivers/i2c/busses/i2c-omap.c
+++ b/drivers/i2c/busses/i2c-omap.c
@@ -299,6 +299,12 @@ static void __omap_i2c_init(struct omap_i2c_dev *dev)
        /* Take the I2C module out of reset: */
        omap_i2c_write_reg(dev, OMAP_I2C_CON_REG, OMAP_I2C_CON_EN);
 
+       /*
+        * NOTE: right after setting CON_EN, STAT_BB could be 0 while the
+        * bus is busy. It will be changed to 1 on the next IP FCLK clock.
+        * udelay(1) will be enough to fix that.
+        */
+
        /*
         * Don't write to this register if the IE state is 0 as it can
         * cause deadlock.
@@ -660,7 +666,11 @@ static int omap_i2c_xfer_msg(struct i2c_adapter *adap,
 
        if (!dev->b_hw && stop)
                w |= OMAP_I2C_CON_STP;
-
+       /*
+        * NOTE: STAT_BB bit could became 1 here if another master occupy
+        * the bus. IP successfully complete transfer when the bus will be
+        * free again (BB reset to 0).
+        */
        omap_i2c_write_reg(dev, OMAP_I2C_CON_REG, w);
 
        /*