[PATCH v2 1/1] i2c: i2c-xiic: fix clearing of bnb irq

[Thilo Zirnstein <thi.zirnstein@gmail.com>]

Add a function for clearing the bnb bit,
It waits for all preconditions before clearing the bnb bit or times out.

Tested on Zynqmp dev board with some custom logic.
Tested-by: Thilo Zirnstein <thi.zirnstein@gmail.com>

Signed-off-by: Thilo Zirnstein <thi.zirnstein@gmail.com>
---
 drivers/i2c/busses/i2c-xiic.c | 42 +++++++++++++++++++++++++++--------
 1 file changed, 33 insertions(+), 9 deletions(-)

diff --git a/drivers/i2c/busses/i2c-xiic.c b/drivers/i2c/busses/i2c-xiic.c
index 5e397a7e63f6..da9cedb86f94 100644
--- a/drivers/i2c/busses/i2c-xiic.c
+++ b/drivers/i2c/busses/i2c-xiic.c
@@ -230,7 +230,9 @@ static const struct timing_regs timing_reg_values[] = {
 
 #define XIIC_RESET_MASK             0xAUL
 
-#define XIIC_PM_TIMEOUT		1000	/* ms */
+#define XIIC_PM_TIMEOUT 1000 /* ms */
+/* timeout waiting for bus busy */
+#define XIIC_BB_TIMEOUT		(msecs_to_jiffies(1))
 /* timeout waiting for the controller to respond */
 #define XIIC_I2C_TIMEOUT	(msecs_to_jiffies(1000))
 /* timeout waiting for the controller finish transfers */
@@ -392,6 +394,30 @@ static int xiic_wait_tx_empty(struct xiic_i2c *i2c)
 	return 0;
 }
 
+static int xiic_clear_en_bnb(struct xiic_i2c *i2c)
+{
+	u8 sr = 0, isr = 0;
+	unsigned long timeout;
+
+	timeout = jiffies + XIIC_BB_TIMEOUT;
+	for (isr = xiic_getreg8(i2c, XIIC_IISR_OFFSET);
+		(isr & XIIC_INTR_BNB_MASK);
+		isr = xiic_getreg8(i2c, XIIC_IISR_OFFSET)) {
+
+		sr = xiic_getreg8(i2c, XIIC_SR_REG_OFFSET);
+		if (sr & XIIC_SR_BUS_BUSY_MASK)
+			xiic_setreg8(i2c, XIIC_IISR_OFFSET, XIIC_INTR_BNB_MASK);
+
+		if (time_after(jiffies, timeout)) {
+			dev_err(i2c->dev, "Failed to clear bnb\n");
+			return -ETIMEDOUT;
+		}
+	}
+
+	xiic_irq_en(i2c, XIIC_INTR_BNB_MASK);
+	return 0;
+}
+
 /**
  * xiic_setclk - Sets the configured clock rate
  * @i2c: Pointer to the xiic device structure
@@ -881,9 +907,6 @@ static irqreturn_t xiic_process(int irq, void *dev_id)
 	}
 
 	if (pend & XIIC_INTR_BNB_MASK) {
-		/* IIC bus has transitioned to not busy */
-		clr |= XIIC_INTR_BNB_MASK;
-
 		/* The bus is not busy, disable BusNotBusy interrupt */
 		xiic_irq_dis(i2c, XIIC_INTR_BNB_MASK);
 
@@ -1028,7 +1051,7 @@ static void xiic_start_recv(struct xiic_i2c *i2c)
 
 		xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET, val);
 
-		xiic_irq_clr_en(i2c, XIIC_INTR_BNB_MASK);
+		xiic_clear_en_bnb(i2c);
 	} else {
 		/*
 		 * If previous message is Tx, make sure that Tx FIFO is empty
@@ -1095,7 +1118,7 @@ static void xiic_start_recv(struct xiic_i2c *i2c)
 
 	if (i2c->nmsgs == 1)
 		/* very last, enable bus not busy as well */
-		xiic_irq_clr_en(i2c, XIIC_INTR_BNB_MASK);
+		xiic_clear_en_bnb(i2c);
 
 	/* the message is tx:ed */
 	i2c->tx_pos = msg->len;
@@ -1179,11 +1202,11 @@ static void xiic_start_send(struct xiic_i2c *i2c)
 		/* Clear any pending Tx empty, Tx Error and then enable them */
 		xiic_irq_clr_en(i2c, XIIC_INTR_TX_EMPTY_MASK |
 				XIIC_INTR_TX_ERROR_MASK |
-				XIIC_INTR_BNB_MASK |
 				((i2c->nmsgs > 1 || xiic_tx_space(i2c)) ?
 				XIIC_INTR_TX_HALF_MASK : 0));
 
 		xiic_fill_tx_fifo(i2c);
+		xiic_clear_en_bnb(i2c);
 	} else {
 		/*
 		 * If previous message is Tx, make sure that Tx FIFO is empty
@@ -1225,8 +1248,9 @@ static void xiic_start_send(struct xiic_i2c *i2c)
 
 		/* Clear any pending Tx empty, Tx Error and then enable them */
 		xiic_irq_clr_en(i2c, XIIC_INTR_TX_EMPTY_MASK |
-				XIIC_INTR_TX_ERROR_MASK |
-				XIIC_INTR_BNB_MASK);
+						XIIC_INTR_TX_ERROR_MASK);
+
+		xiic_clear_en_bnb(i2c);
 	}
 
 	i2c->prev_msg_tx = true;
-- 
2.43.0