[PATCH v3 0/2] i2c: i2c-xiic: fix clearing of bnb irq and waiting/ clearing while atomic

[PATCH v3 0/2] i2c: i2c-xiic: fix clearing of bnb irq and waiting/ clearing while atomic

[Thilo Zirnstein]

Dear all,

This patch-series fixes the clearing routine for the bus not busy (bnb) irq
plus the waiting and clearing routines while in atomic context.

The bnb is used to indicate that the current transfer is done.
A high level view of the software flow for tx:

* init i2c controller
* prepare all registers ( fill fifo, enable irqs, ... )
* start i2c txfer
* clear and enable bnb
* wait for completion
* ( serve interrupts )
* ( bnb interrupt ): complete completion

The datasheet ( pg090-axi-iic, Interrupt-Status-Register ISR)
states that the bnb bit can only be cleared if
the bus busy bit in the status register is set.
So the iic controller must have recognized that their is some activity
on the bus. ( Start condition )

Currently the bnb bit is cleared without checking or waiting for this
condition. This can lead to spurious bnb interrupts.

Andi suggested to use an atomic-save function to wait for bnb.
This was applied for other waiting/ clearing functions, too.

One question left:

Are the timeouts fine, while in an atomic context ?
One second seems to be rather high.

Kind regards,

Thilo Zirnstein
---

Changes in v3
- Use atomic-save functions for waiting and clearing.
- Fix intendation
- Unintentional changes removed

Changes in v2:
- Unintentional changes removed.

Thilo Zirnstein (2):
  i2c: i2c-xiic: fix clearing of bnb irq
  i2c: i2c-xiic: fix waiting/clearing while atomic

 drivers/i2c/busses/i2c-xiic.c | 68 ++++++++++++++++++++++++++++-------
 1 file changed, 55 insertions(+), 13 deletions(-)

--
2.43.0

[PATCH v3 1/2] i2c: i2c-xiic: fix clearing of bnb irq

[Thilo Zirnstein]

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

Signed-off-by: Thilo Zirnstein <thi.zirnstein@gmail.com>
---
 drivers/i2c/busses/i2c-xiic.c | 40 ++++++++++++++++++++++++++++-------
 1 file changed, 32 insertions(+), 8 deletions(-)

diff --git a/drivers/i2c/busses/i2c-xiic.c b/drivers/i2c/busses/i2c-xiic.c
index ba560462d451..e68e17bdf0ba 100644
--- a/drivers/i2c/busses/i2c-xiic.c
+++ b/drivers/i2c/busses/i2c-xiic.c
@@ -233,6 +233,8 @@ static const struct timing_regs timing_reg_values[] = {
 #define XIIC_RESET_MASK             0xAUL

 #define XIIC_PM_TIMEOUT		1000	/* ms */
+/* timeout waiting for bus busy */
+#define XIIC_BB_TIMEOUT_US	1000
 /* timeout waiting for the controller to respond */
 #define XIIC_I2C_TIMEOUT	(msecs_to_jiffies(1000))
 /* timeout waiting for the controller finish transfers */
@@ -394,6 +396,30 @@ static int xiic_wait_tx_empty(struct xiic_i2c *i2c)
 	return 0;
 }

+static void xiic_clear_en_bnb(struct xiic_i2c *i2c)
+{
+	u8 sr = 0, isr = 0;
+	int ret;
+
+	isr = xiic_getreg8(i2c, XIIC_IISR_OFFSET);
+	if (!(isr & XIIC_INTR_BNB_MASK)) {
+		xiic_irq_en(i2c, XIIC_INTR_BNB_MASK);
+		return;
+	}
+
+	ret = read_poll_timeout_atomic(xiic_getreg8, sr,
+			sr & XIIC_SR_BUS_BUSY_MASK, 0, XIIC_BB_TIMEOUT_US, 0,
+			i2c, XIIC_SR_REG_OFFSET);
+
+	if (ret) {
+		dev_err(i2c->dev, "Failed to clear bnb\n");
+		return;
+	}
+
+	xiic_setreg8(i2c, XIIC_IISR_OFFSET, XIIC_INTR_BNB_MASK);
+	xiic_irq_en(i2c, XIIC_INTR_BNB_MASK);
+}
+
 /**
  * xiic_setclk - Sets the configured clock rate
  * @i2c: Pointer to the xiic device structure
@@ -883,9 +909,6 @@ 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);

@@ -1030,7 +1053,7 @@ 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
@@ -1097,7 +1120,7 @@ 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;
@@ -1181,11 +1204,11 @@ 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
@@ -1227,8 +1250,9 @@ 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

[PATCH v3 2/2] i2c: i2c-xiic: fix waiting/clearing while atomic

[Thilo Zirnstein]

Use non jiffies based waiting functions,
if in atomic context.

Suggested-by: Andi Shyti <andi.shyti@kernel.org>
Signed-off-by: Thilo Zirnstein <thi.zirnstein@gmail.com>
---
 drivers/i2c/busses/i2c-xiic.c | 28 +++++++++++++++++++++++-----
 1 file changed, 23 insertions(+), 5 deletions(-)

diff --git a/drivers/i2c/busses/i2c-xiic.c b/drivers/i2c/busses/i2c-xiic.c
index e68e17bdf0ba..fc9a0628cb67 100644
--- a/drivers/i2c/busses/i2c-xiic.c
+++ b/drivers/i2c/busses/i2c-xiic.c
@@ -359,16 +359,28 @@ static inline void xiic_irq_clr_en(struct xiic_i2c *i2c, u32 mask)
 	xiic_irq_en(i2c, mask);
 }

+static int xiic_poll_rx_empty(struct xiic_i2c *i2c)
+{
+	if (xiic_getreg8(i2c, XIIC_SR_REG_OFFSET) &
+	    XIIC_SR_RX_FIFO_EMPTY_MASK)
+		return 1;
+
+	xiic_getreg8(i2c, XIIC_DRR_REG_OFFSET);
+	return 0;
+}
+
 static int xiic_clear_rx_fifo(struct xiic_i2c *i2c)
 {
-	u8 sr;
+	int rx_empty;
 	unsigned long timeout;

+	if (i2c->atomic)
+		return read_poll_timeout_atomic(xiic_poll_rx_empty,
+				rx_empty, rx_empty, 10, XIIC_I2C_TIMEOUT,
+				0, i2c);
+
 	timeout = jiffies + XIIC_I2C_TIMEOUT;
-	for (sr = xiic_getreg8(i2c, XIIC_SR_REG_OFFSET);
-		!(sr & XIIC_SR_RX_FIFO_EMPTY_MASK);
-		sr = xiic_getreg8(i2c, XIIC_SR_REG_OFFSET)) {
-		xiic_getreg8(i2c, XIIC_DRR_REG_OFFSET);
+	while (!xiic_poll_rx_empty(i2c)) {
 		if (time_after(jiffies, timeout)) {
 			dev_err(i2c->dev, "Failed to clear rx fifo\n");
 			return -ETIMEDOUT;
@@ -383,6 +395,12 @@ static int xiic_wait_tx_empty(struct xiic_i2c *i2c)
 	u8 isr;
 	unsigned long timeout;

+	if (i2c->atomic)
+		return read_poll_timeout_atomic(xiic_getreg32, isr,
+				isr & XIIC_INTR_TX_EMPTY_MASK, 10,
+				XIIC_I2C_TIMEOUT, 0, i2c,
+				XIIC_IISR_OFFSET);
+
 	timeout = jiffies + XIIC_I2C_TIMEOUT;
 	for (isr = xiic_getreg32(i2c, XIIC_IISR_OFFSET);
 		!(isr & XIIC_INTR_TX_EMPTY_MASK);
--
2.43.0