i2c-designware: enable/disable the controller properly

The correct way to disable or enable the controller is to wait until the
DW_IC_ENABLE_STATUS register bit matches the bit we program into DW_IC_ENABLE
register. This procedure is described in the DesignWare I2C databook.

By doing this we can be sure that the controller is in correct state once
the function returns.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

1 files changed, 28 insertions, 6 deletions

diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
index 94fd81875409..5cc4ebf29b0a 100644
--- a/drivers/i2c/busses/i2c-designware-core.c
+++ b/drivers/i2c/busses/i2c-designware-core.c
@@ -68,6 +68,7 @@
 #define DW_IC_TXFLR             0x74
 #define DW_IC_RXFLR             0x78
 #define DW_IC_TX_ABRT_SOURCE    0x80
+#define DW_IC_ENABLE_STATUS     0x9c
 #define DW_IC_COMP_PARAM_1      0xf4
 #define DW_IC_COMP_TYPE         0xfc
 #define DW_IC_COMP_TYPE_VALUE   0x44570140
@@ -248,6 +249,27 @@ static u32 i2c_dw_scl_lcnt(u32 ic_clk, u32 tLOW, u32 tf, int offset)
         return ((ic_clk * (tLOW + tf) + 5000) / 10000) - 1 + offset;
 }
 
+static void __i2c_dw_enable(struct dw_i2c_dev *dev, bool enable)
+{
+        int timeout = 100;
+
+        do {
+                dw_writel(dev, enable, DW_IC_ENABLE);
+                if ((dw_readl(dev, DW_IC_ENABLE_STATUS) & 1) == enable)
+                        return;
+
+                /*
+                 * Wait 10 times the signaling period of the highest I2C
+                 * transfer supported by the driver (for 400KHz this is
+                 * 25us) as described in the DesignWare I2C databook.
+                 */
+                usleep_range(25, 250);
+        } while (timeout--);
+
+        dev_warn(dev->dev, "timeout in %sabling adapter\n",
+                 enable ? "en" : "dis");
+}
+
 /**
  * i2c_dw_init() - initialize the designware i2c master hardware
  * @dev: device private data
@@ -278,7 +300,7 @@ int i2c_dw_init(struct dw_i2c_dev *dev)
         }
 
         /* Disable the adapter */
-        dw_writel(dev, 0, DW_IC_ENABLE);
+        __i2c_dw_enable(dev, false);
 
         /* set standard and fast speed deviders for high/low periods */
 
@@ -345,7 +367,7 @@ static void i2c_dw_xfer_init(struct dw_i2c_dev *dev)
         u32 ic_con;
 
         /* Disable the adapter */
-        dw_writel(dev, 0, DW_IC_ENABLE);
+        __i2c_dw_enable(dev, false);
 
         /* set the slave (target) address */
         dw_writel(dev, msgs[dev->msg_write_idx].addr, DW_IC_TAR);
@@ -359,7 +381,7 @@ static void i2c_dw_xfer_init(struct dw_i2c_dev *dev)
         dw_writel(dev, ic_con, DW_IC_CON);
 
         /* Enable the adapter */
-        dw_writel(dev, 1, DW_IC_ENABLE);
+        __i2c_dw_enable(dev, true);
 
         /* Enable interrupts */
         dw_writel(dev, DW_IC_INTR_DEFAULT_MASK, DW_IC_INTR_MASK);
@@ -565,7 +587,7 @@ i2c_dw_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
         /* no error */
         if (likely(!dev->cmd_err)) {
                 /* Disable the adapter */
-                dw_writel(dev, 0, DW_IC_ENABLE);
+                __i2c_dw_enable(dev, false);
                 ret = num;
                 goto done;
         }
@@ -700,7 +722,7 @@ EXPORT_SYMBOL_GPL(i2c_dw_isr);
 void i2c_dw_enable(struct dw_i2c_dev *dev)
 {
        /* Enable the adapter */
-        dw_writel(dev, 1, DW_IC_ENABLE);
+        __i2c_dw_enable(dev, true);
 }
 EXPORT_SYMBOL_GPL(i2c_dw_enable);
 
@@ -713,7 +735,7 @@ EXPORT_SYMBOL_GPL(i2c_dw_is_enabled);
 void i2c_dw_disable(struct dw_i2c_dev *dev)
 {
         /* Disable controller */
-        dw_writel(dev, 0, DW_IC_ENABLE);
+        __i2c_dw_enable(dev, false);
 
         /* Disable all interupts */
         dw_writel(dev, 0, DW_IC_INTR_MASK);