Revert "i2c: designware: do not disable adapter after transfer"

This reverts commit 0317e6c0f1dc1ba86b8d9dccc010c5e77b8355fa.

Srinivas reported recently touchscreen and touchpad stopped working in
Haswell based machine in Linux 4.9-rc series with timeout errors from
i2c_designware:

[   16.508013] i2c_designware INT33C3:00: controller timed out
[   16.508302] i2c_hid i2c-MSFT0001:02: failed to change power setting.
[   17.532016] i2c_designware INT33C3:00: controller timed out
[   18.556022] i2c_designware INT33C3:00: controller timed out
[   18.556315] i2c_hid i2c-ATML1000:00: failed to retrieve report from device.

I managed to reproduce similar errors on another Haswell based machine
where touchscreen initialization fails maybe in every 1/5 - 1/2 boots.
Since root cause for these errors is not clear yet and debugging is
ongoing it's better to revert this commit as we are near to release.

Reported-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
Signed-off-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>

1 files changed, 18 insertions, 37 deletions

diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
index c53058d6139c..b403fa5ecf49 100644
--- a/drivers/i2c/busses/i2c-designware-core.c
+++ b/drivers/i2c/busses/i2c-designware-core.c
@@ -91,9 +91,7 @@
                                          DW_IC_INTR_TX_ABRT | \
                                          DW_IC_INTR_STOP_DET)
 
-#define DW_IC_STATUS_ACTIVITY           0x1
-#define DW_IC_STATUS_TFE                BIT(2)
-#define DW_IC_STATUS_MST_ACTIVITY       BIT(5)
+#define DW_IC_STATUS_ACTIVITY   0x1
 
 #define DW_IC_SDA_HOLD_RX_SHIFT         16
 #define DW_IC_SDA_HOLD_RX_MASK          GENMASK(23, DW_IC_SDA_HOLD_RX_SHIFT)
@@ -478,25 +476,9 @@ static void i2c_dw_xfer_init(struct dw_i2c_dev *dev)
 {
         struct i2c_msg *msgs = dev->msgs;
         u32 ic_tar = 0;
-        bool enabled;
 
-        enabled = dw_readl(dev, DW_IC_ENABLE_STATUS) & 1;
-
-        if (enabled) {
-                u32 ic_status;
-
-                /*
-                 * Only disable adapter if ic_tar and ic_con can't be
-                 * dynamically updated
-                 */
-                ic_status = dw_readl(dev, DW_IC_STATUS);
-                if (!dev->dynamic_tar_update_enabled ||
-                    (ic_status & DW_IC_STATUS_MST_ACTIVITY) ||
-                    !(ic_status & DW_IC_STATUS_TFE)) {
-                        __i2c_dw_enable_and_wait(dev, false);
-                        enabled = false;
-                }
-        }
+        /* Disable the adapter */
+        __i2c_dw_enable_and_wait(dev, false);
 
         /* if the slave address is ten bit address, enable 10BITADDR */
         if (dev->dynamic_tar_update_enabled) {
@@ -526,8 +508,8 @@ static void i2c_dw_xfer_init(struct dw_i2c_dev *dev)
         /* enforce disabled interrupts (due to HW issues) */
         i2c_dw_disable_int(dev);
 
-        if (!enabled)
-                __i2c_dw_enable(dev, true);
+        /* Enable the adapter */
+        __i2c_dw_enable(dev, true);
 
         /* Clear and enable interrupts */
         dw_readl(dev, DW_IC_CLR_INTR);
@@ -708,8 +690,7 @@ static int i2c_dw_handle_tx_abort(struct dw_i2c_dev *dev)
 }
 
 /*
- * Prepare controller for a transaction and start transfer by calling
- * i2c_dw_xfer_init()
+ * Prepare controller for a transaction and call i2c_dw_xfer_msg
  */
 static int
 i2c_dw_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
@@ -752,6 +733,16 @@ i2c_dw_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
                 goto done;
         }
 
+        /*
+         * We must disable the adapter before returning and signaling the end
+         * of the current transfer. Otherwise the hardware might continue
+         * generating interrupts which in turn causes a race condition with
+         * the following transfer.  Needs some more investigation if the
+         * additional interrupts are a hardware bug or this driver doesn't
+         * handle them correctly yet.
+         */
+        __i2c_dw_enable(dev, false);
+
         if (dev->msg_err) {
                 ret = dev->msg_err;
                 goto done;
@@ -893,19 +884,9 @@ static irqreturn_t i2c_dw_isr(int this_irq, void *dev_id)
          */
 
 tx_aborted:
-        if ((stat & (DW_IC_INTR_TX_ABRT | DW_IC_INTR_STOP_DET))
-                        || dev->msg_err) {
-                /*
-                 * We must disable interruts before returning and signaling
-                 * the end of the current transfer. Otherwise the hardware
-                 * might continue generating interrupts for non-existent
-                 * transfers.
-                 */
-                i2c_dw_disable_int(dev);
-                dw_readl(dev, DW_IC_CLR_INTR);
-
+        if ((stat & (DW_IC_INTR_TX_ABRT | DW_IC_INTR_STOP_DET)) || dev->msg_err)
                 complete(&dev->cmd_complete);
-        } else if (unlikely(dev->accessor_flags & ACCESS_INTR_MASK)) {
+        else if (unlikely(dev->accessor_flags & ACCESS_INTR_MASK)) {
                 /* workaround to trigger pending interrupt */
                 stat = dw_readl(dev, DW_IC_INTR_MASK);
                 i2c_dw_disable_int(dev);