i2c: rcar: refactor handling of first message

After moving ICMSR handling to interrupt handlers previously to fix a
race condition, we can now also move ICMSR handling for the first
message out of the function to prepare a message. By introducing a
seperate function to initialize the first message, we can not only
remove some code duplication but the remaining code is also easier to
follow. The function to prepare a message is much simpler without ICMSR
handling.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>

diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
index cfc49c3..6e932f9 100644 (file)
--- a/drivers/i2c/busses/i2c-rcar.c
+++ b/drivers/i2c/busses/i2c-rcar.c
@@ -98,7 +98,6 @@
 #define RCAR_IRQ_STOP  (MST)
 
 #define ID_LAST_MSG    (1 << 0)
-#define ID_FIRST_MSG   (1 << 1)
 #define ID_DONE                (1 << 2)
 #define ID_ARBLOST     (1 << 3)
 #define ID_NACK                (1 << 4)
@@ -333,11 +332,19 @@ scgd_find:
        return 0;
 }
 
+/*
+ * We don't have a test case but the HW engineers say that the write order of
+ * ICMSR and ICMCR depends on whether we issue START or REP_START. So, ICMSR
+ * handling is outside of this function. First messages clear ICMSR before this
+ * function, interrupt handlers clear the relevant bits after this function.
+ */
 static void rcar_i2c_prepare_msg(struct rcar_i2c_priv *priv)
 {
        int read = !!rcar_i2c_is_recv(priv);
 
        priv->pos = 0;
+       priv->flags &= ID_P_MASK;
+
        if (priv->msgs_left == 1)
                priv->flags |= ID_LAST_MSG;
 
@@ -345,29 +352,27 @@ static void rcar_i2c_prepare_msg(struct rcar_i2c_priv *priv)
        if (!priv->atomic_xfer)
                rcar_i2c_write(priv, ICMIER, read ? RCAR_IRQ_RECV : RCAR_IRQ_SEND);
 
-       /*
-        * We don't have a test case but the HW engineers say that the write order
-        * of ICMSR and ICMCR depends on whether we issue START or REP_START. Since
-        * it didn't cause a drawback for me, let's rather be safe than sorry.
-        */
-       if (priv->flags & ID_FIRST_MSG) {
-               rcar_i2c_write(priv, ICMSR, 0);
+       if (priv->flags & ID_P_REP_AFTER_RD)
+               priv->flags &= ~ID_P_REP_AFTER_RD;
+       else
                rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_START);
-       } else {
-               if (priv->flags & ID_P_REP_AFTER_RD)
-                       priv->flags &= ~ID_P_REP_AFTER_RD;
-               else
-                       rcar_i2c_write(priv, ICMCR, RCAR_BUS_PHASE_START);
-               /* ICMSR is cleared in interrupt handlers */
-       }
+}
+
+static void rcar_i2c_first_msg(struct rcar_i2c_priv *priv,
+                              struct i2c_msg *msgs, int num)
+{
+       priv->msg = msgs;
+       priv->msgs_left = num;
+       rcar_i2c_write(priv, ICMSR, 0); /* must be before preparing msg */
+       rcar_i2c_prepare_msg(priv);
 }
 
 static void rcar_i2c_next_msg(struct rcar_i2c_priv *priv)
 {
        priv->msg++;
        priv->msgs_left--;
-       priv->flags &= ID_P_MASK;
        rcar_i2c_prepare_msg(priv);
+       /* ICMSR handling must come afterwards in the irq handler */
 }
 
 static void rcar_i2c_cleanup_dma(struct rcar_i2c_priv *priv, bool terminate)
@@ -852,11 +857,7 @@ static int rcar_i2c_master_xfer(struct i2c_adapter *adap,
        for (i = 0; i < num; i++)
                rcar_i2c_request_dma(priv, msgs + i);
 
-       /* init first message */
-       priv->msg = msgs;
-       priv->msgs_left = num;
-       priv->flags = (priv->flags & ID_P_MASK) | ID_FIRST_MSG;
-       rcar_i2c_prepare_msg(priv);
+       rcar_i2c_first_msg(priv, msgs, num);
 
        time_left = wait_event_timeout(priv->wait, priv->flags & ID_DONE,
                                     num * adap->timeout);
@@ -906,12 +907,7 @@ static int rcar_i2c_master_xfer_atomic(struct i2c_adapter *adap,
                goto out;
 
        rcar_i2c_init(priv);
-
-       /* init first message */
-       priv->msg = msgs;
-       priv->msgs_left = num;
-       priv->flags = (priv->flags & ID_P_MASK) | ID_FIRST_MSG;
-       rcar_i2c_prepare_msg(priv);
+       rcar_i2c_first_msg(priv, msgs, num);
 
        j = jiffies + num * adap->timeout;
        do {