Rework the read and write code paths in the driver to support operation
in atomic contexts.

Similar changes have been implemented in other drivers, including:
commit 3a5ee18d2a32 ("i2c: imx: implement master_xfer_atomic callback")
commit 445094c8a9fb ("i2c: exynos5: add support for atomic transfers")
commit ede2299f7101 ("i2c: tegra: Support atomic transfers")
commit fe402bd09049 ("i2c: meson: implement the master_xfer_atomic
callback")

Signed-off-by: Manikanta Guntupalli <manikanta.guntupalli@amd.com>
---
 drivers/i2c/busses/i2c-xiic.c | 245 +++++++++++++++++++++++++++++-----
 1 file changed, 212 insertions(+), 33 deletions(-)

diff --git a/drivers/i2c/busses/i2c-xiic.c b/drivers/i2c/busses/i2c-xiic.c
index 052bae4fc664..e5e9a4993bd4 100644
--- a/drivers/i2c/busses/i2c-xiic.c
+++ b/drivers/i2c/busses/i2c-xiic.c
@@ -30,6 +30,8 @@
 #include <linux/of.h>
 #include <linux/clk.h>
 #include <linux/pm_runtime.h>
+#include <linux/iopoll.h>
+#include <linux/spinlock.h>
 
 #define DRIVER_NAME "xiic-i2c"
 #define DYNAMIC_MODE_READ_BROKEN_BIT	BIT(0)
@@ -74,6 +76,9 @@ enum i2c_scl_freq {
  * @smbus_block_read: Flag to handle block read
  * @input_clk: Input clock to I2C controller
  * @i2c_clk: I2C SCL frequency
+ * @atomic: Mode of transfer
+ * @atomic_lock: Lock for atomic transfer mode
+ * @atomic_xfer_state: See STATE_
  */
 struct xiic_i2c {
 	struct device *dev;
@@ -96,6 +101,9 @@ struct xiic_i2c {
 	bool smbus_block_read;
 	unsigned long input_clk;
 	unsigned int i2c_clk;
+	bool atomic;
+	spinlock_t atomic_lock;		/* Lock for atomic transfer mode */
+	enum xilinx_i2c_state atomic_xfer_state;
 };
 
 struct xiic_version_data {
@@ -224,6 +232,8 @@ static const struct timing_regs timing_reg_values[] = {
 #define XIIC_I2C_TIMEOUT	(msecs_to_jiffies(1000))
 /* timeout waiting for the controller finish transfers */
 #define XIIC_XFER_TIMEOUT	(msecs_to_jiffies(10000))
+/* timeout waiting for the controller finish transfers in micro seconds */
+#define XIIC_XFER_TIMEOUT_US	10000000
 
 /*
  * The following constant is used for the device global interrupt enable
@@ -238,7 +248,7 @@ static const struct timing_regs timing_reg_values[] = {
 static int xiic_start_xfer(struct xiic_i2c *i2c, struct i2c_msg *msgs, int num);
 static void __xiic_start_xfer(struct xiic_i2c *i2c);
 
-static int __maybe_unused xiic_i2c_runtime_suspend(struct device *dev)
+static int xiic_i2c_runtime_suspend(struct device *dev)
 {
 	struct xiic_i2c *i2c = dev_get_drvdata(dev);
 
@@ -247,7 +257,7 @@ static int __maybe_unused xiic_i2c_runtime_suspend(struct device *dev)
 	return 0;
 }
 
-static int __maybe_unused xiic_i2c_runtime_resume(struct device *dev)
+static int xiic_i2c_runtime_resume(struct device *dev)
 {
 	struct xiic_i2c *i2c = dev_get_drvdata(dev);
 	int ret;
@@ -397,9 +407,10 @@ static int xiic_setclk(struct xiic_i2c *i2c)
 	unsigned int index = 0;
 	u32 reg_val;
 
-	dev_dbg(i2c->adap.dev.parent,
-		"%s entry, i2c->input_clk: %ld, i2c->i2c_clk: %d\n",
-		__func__, i2c->input_clk, i2c->i2c_clk);
+	if (!i2c->atomic)
+		dev_dbg(i2c->adap.dev.parent,
+			"%s entry, i2c->input_clk: %ld, i2c->i2c_clk: %d\n",
+			__func__, i2c->input_clk, i2c->i2c_clk);
 
 	/* If not specified in DT, do not configure in SW. Rely only on Vivado design */
 	if (!i2c->i2c_clk || !i2c->input_clk)
@@ -490,7 +501,8 @@ static int xiic_reinit(struct xiic_i2c *i2c)
 		return ret;
 
 	/* Enable interrupts */
-	xiic_setreg32(i2c, XIIC_DGIER_OFFSET, XIIC_GINTR_ENABLE_MASK);
+	if (!i2c->atomic)
+		xiic_setreg32(i2c, XIIC_DGIER_OFFSET, XIIC_GINTR_ENABLE_MASK);
 
 	xiic_irq_clr_en(i2c, XIIC_INTR_ARB_LOST_MASK);
 
@@ -572,11 +584,12 @@ static void xiic_read_rx(struct xiic_i2c *i2c)
 
 	bytes_in_fifo = xiic_getreg8(i2c, XIIC_RFO_REG_OFFSET) + 1;
 
-	dev_dbg(i2c->adap.dev.parent,
-		"%s entry, bytes in fifo: %d, rem: %d, SR: 0x%x, CR: 0x%x\n",
-		__func__, bytes_in_fifo, xiic_rx_space(i2c),
-		xiic_getreg8(i2c, XIIC_SR_REG_OFFSET),
-		xiic_getreg8(i2c, XIIC_CR_REG_OFFSET));
+	if (!i2c->atomic)
+		dev_dbg(i2c->adap.dev.parent,
+			"%s entry, bytes in fifo: %d, rem: %d, SR: 0x%x, CR: 0x%x\n",
+			__func__, bytes_in_fifo, xiic_rx_space(i2c),
+			xiic_getreg8(i2c, XIIC_SR_REG_OFFSET),
+			xiic_getreg8(i2c, XIIC_CR_REG_OFFSET));
 
 	if (bytes_in_fifo > xiic_rx_space(i2c))
 		bytes_in_fifo = xiic_rx_space(i2c);
@@ -635,6 +648,26 @@ static void xiic_read_rx(struct xiic_i2c *i2c)
 	}
 }
 
+static bool xiic_error_check(struct xiic_i2c *i2c)
+{
+	bool status = false;
+	u32 pend, isr, ier;
+
+	isr = xiic_getreg32(i2c, XIIC_IISR_OFFSET);
+	ier = xiic_getreg32(i2c, XIIC_IIER_OFFSET);
+	pend = isr & ier;
+
+	if ((pend & XIIC_INTR_ARB_LOST_MASK) ||
+	    ((pend & XIIC_INTR_TX_ERROR_MASK) &&
+	    !(pend & XIIC_INTR_RX_FULL_MASK))) {
+		xiic_reinit(i2c);
+		status = true;
+		if (i2c->tx_msg || i2c->rx_msg)
+			i2c->atomic_xfer_state = STATE_ERROR;
+	}
+	return status;
+}
+
 static int xiic_tx_fifo_space(struct xiic_i2c *i2c)
 {
 	/* return the actual space left in the FIFO */
@@ -648,8 +681,9 @@ static void xiic_fill_tx_fifo(struct xiic_i2c *i2c)
 
 	len = (len > fifo_space) ? fifo_space : len;
 
-	dev_dbg(i2c->adap.dev.parent, "%s entry, len: %d, fifo space: %d\n",
-		__func__, len, fifo_space);
+	if (!i2c->atomic)
+		dev_dbg(i2c->adap.dev.parent, "%s entry, len: %d, fifo space: %d\n",
+			__func__, len, fifo_space);
 
 	while (len--) {
 		u16 data = i2c->tx_msg->buf[i2c->tx_pos++];
@@ -672,9 +706,13 @@ static void xiic_fill_tx_fifo(struct xiic_i2c *i2c)
 				xiic_setreg8(i2c, XIIC_CR_REG_OFFSET, cr &
 					     ~XIIC_CR_MSMS_MASK);
 			}
-			dev_dbg(i2c->adap.dev.parent, "%s TX STOP\n", __func__);
+			if (!i2c->atomic)
+				dev_dbg(i2c->adap.dev.parent, "%s TX STOP\n", __func__);
 		}
 		xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET, data);
+
+		if (i2c->atomic && xiic_error_check(i2c))
+			return;
 	}
 }
 
@@ -877,22 +915,55 @@ static int xiic_wait_not_busy(struct xiic_i2c *i2c)
 	 */
 	err = xiic_bus_busy(i2c);
 	while (err && tries--) {
-		msleep(1);
+		if (i2c->atomic)
+			udelay(1000);
+		else
+			usleep_range(1000, 1100);
 		err = xiic_bus_busy(i2c);
 	}
 
 	return err;
 }
 
+static void xiic_recv_atomic(struct xiic_i2c *i2c)
+{
+	while (xiic_rx_space(i2c)) {
+		if (xiic_getreg32(i2c, XIIC_IISR_OFFSET) & XIIC_INTR_RX_FULL_MASK) {
+			if (!i2c->rx_msg) {
+				xiic_clear_rx_fifo(i2c);
+				break;
+			}
+			xiic_read_rx(i2c);
+
+			/* Clear Rx full and Tx error interrupts. */
+			xiic_irq_clr_en(i2c, XIIC_INTR_RX_FULL_MASK |
+					XIIC_INTR_TX_ERROR_MASK);
+		}
+		if (xiic_error_check(i2c))
+			return;
+	}
+
+	i2c->rx_msg = NULL;
+	xiic_irq_clr_en(i2c, XIIC_INTR_TX_ERROR_MASK);
+
+	/* send next message if this wasn't the last. */
+	if (i2c->nmsgs > 1) {
+		i2c->nmsgs--;
+		i2c->tx_msg++;
+		__xiic_start_xfer(i2c);
+	}
+}
+
 static void xiic_start_recv(struct xiic_i2c *i2c)
 {
 	u16 rx_watermark;
 	u8 cr = 0, rfd_set = 0;
 	struct i2c_msg *msg = i2c->rx_msg = i2c->tx_msg;
 
-	dev_dbg(i2c->adap.dev.parent, "%s entry, ISR: 0x%x, CR: 0x%x\n",
-		__func__, xiic_getreg32(i2c, XIIC_IISR_OFFSET),
-		xiic_getreg8(i2c, XIIC_CR_REG_OFFSET));
+	if (!i2c->atomic)
+		dev_dbg(i2c->adap.dev.parent, "%s entry, ISR: 0x%x, CR: 0x%x\n",
+			__func__, xiic_getreg32(i2c, XIIC_IISR_OFFSET),
+			xiic_getreg8(i2c, XIIC_CR_REG_OFFSET));
 
 	/* Disable Tx interrupts */
 	xiic_irq_dis(i2c, XIIC_INTR_TX_HALF_MASK | XIIC_INTR_TX_EMPTY_MASK);
@@ -990,9 +1061,10 @@ static void xiic_start_recv(struct xiic_i2c *i2c)
 					XIIC_CR_MSMS_MASK)
 					& ~(XIIC_CR_DIR_IS_TX_MASK));
 		}
-		dev_dbg(i2c->adap.dev.parent, "%s end, ISR: 0x%x, CR: 0x%x\n",
-			__func__, xiic_getreg32(i2c, XIIC_IISR_OFFSET),
-			xiic_getreg8(i2c, XIIC_CR_REG_OFFSET));
+		if (!i2c->atomic)
+			dev_dbg(i2c->adap.dev.parent, "%s end, ISR: 0x%x, CR: 0x%x\n",
+				__func__, xiic_getreg32(i2c, XIIC_IISR_OFFSET),
+				xiic_getreg8(i2c, XIIC_CR_REG_OFFSET));
 	}
 
 	if (i2c->nmsgs == 1)
@@ -1002,10 +1074,57 @@ static void xiic_start_recv(struct xiic_i2c *i2c)
 	/* the message is tx:ed */
 	i2c->tx_pos = msg->len;
 
+	i2c->prev_msg_tx = false;
+
 	/* Enable interrupts */
-	xiic_setreg32(i2c, XIIC_DGIER_OFFSET, XIIC_GINTR_ENABLE_MASK);
+	if (!i2c->atomic)
+		xiic_setreg32(i2c, XIIC_DGIER_OFFSET, XIIC_GINTR_ENABLE_MASK);
+	else
+		xiic_recv_atomic(i2c);
+}
 
-	i2c->prev_msg_tx = false;
+static void xiic_send_rem_atomic(struct xiic_i2c *i2c)
+{
+	if (!i2c->tx_msg)
+		goto send_atomic_out;
+	while (xiic_tx_space(i2c)) {
+		if (xiic_tx_fifo_space(i2c)) {
+			u16 data;
+
+			data = i2c->tx_msg->buf[i2c->tx_pos];
+			i2c->tx_pos++;
+			if (!xiic_tx_space(i2c) && i2c->nmsgs == 1) {
+				/* last message in transfer -> STOP */
+				if (i2c->dynamic) {
+					data |= XIIC_TX_DYN_STOP_MASK;
+				} else {
+					u8 cr;
+					int status;
+
+					/* Wait till FIFO is empty so STOP is sent last */
+					status = xiic_wait_tx_empty(i2c);
+					if (status)
+						return;
+
+					/* Write to CR to stop */
+					cr = xiic_getreg8(i2c, XIIC_CR_REG_OFFSET);
+					xiic_setreg8(i2c, XIIC_CR_REG_OFFSET, cr &
+						     ~XIIC_CR_MSMS_MASK);
+				}
+			}
+			xiic_setreg16(i2c, XIIC_DTR_REG_OFFSET, data);
+		}
+		if (xiic_error_check(i2c))
+			return;
+	}
+send_atomic_out:
+	if (i2c->nmsgs > 1) {
+		i2c->nmsgs--;
+		i2c->tx_msg++;
+		__xiic_start_xfer(i2c);
+	} else {
+		xiic_irq_dis(i2c, XIIC_INTR_TX_HALF_MASK);
+	}
 }
 
 static void xiic_start_send(struct xiic_i2c *i2c)
@@ -1014,11 +1133,13 @@ static void xiic_start_send(struct xiic_i2c *i2c)
 	u16 data;
 	struct i2c_msg *msg = i2c->tx_msg;
 
-	dev_dbg(i2c->adap.dev.parent, "%s entry, msg: %p, len: %d",
-		__func__, msg, msg->len);
-	dev_dbg(i2c->adap.dev.parent, "%s entry, ISR: 0x%x, CR: 0x%x\n",
-		__func__, xiic_getreg32(i2c, XIIC_IISR_OFFSET),
-		xiic_getreg8(i2c, XIIC_CR_REG_OFFSET));
+	if (!i2c->atomic) {
+		dev_dbg(i2c->adap.dev.parent, "%s entry, msg: %p, len: %d",
+			__func__, msg, msg->len);
+		dev_dbg(i2c->adap.dev.parent, "%s entry, ISR: 0x%x, CR: 0x%x\n",
+			__func__, xiic_getreg32(i2c, XIIC_IISR_OFFSET),
+			xiic_getreg8(i2c, XIIC_CR_REG_OFFSET));
+	}
 
 	if (i2c->dynamic) {
 		/* write the address */
@@ -1083,19 +1204,27 @@ static void xiic_start_send(struct xiic_i2c *i2c)
 				XIIC_INTR_TX_ERROR_MASK |
 				XIIC_INTR_BNB_MASK);
 	}
+
 	i2c->prev_msg_tx = true;
+
+	if (i2c->atomic && !i2c->atomic_xfer_state)
+		xiic_send_rem_atomic(i2c);
 }
 
 static void __xiic_start_xfer(struct xiic_i2c *i2c)
 {
 	int fifo_space = xiic_tx_fifo_space(i2c);
 
-	dev_dbg(i2c->adap.dev.parent, "%s entry, msg: %p, fifos space: %d\n",
-		__func__, i2c->tx_msg, fifo_space);
+	if (!i2c->atomic)
+		dev_dbg(i2c->adap.dev.parent, "%s entry, msg: %p, fifos space: %d\n",
+			__func__, i2c->tx_msg, fifo_space);
 
 	if (!i2c->tx_msg)
 		return;
 
+	if (i2c->atomic && xiic_error_check(i2c))
+		return;
+
 	i2c->rx_pos = 0;
 	i2c->tx_pos = 0;
 	i2c->state = STATE_START;
@@ -1112,7 +1241,10 @@ static int xiic_start_xfer(struct xiic_i2c *i2c, struct i2c_msg *msgs, int num)
 	bool broken_read, max_read_len, smbus_blk_read;
 	int ret, count;
 
-	mutex_lock(&i2c->lock);
+	if (i2c->atomic)
+		spin_lock(&i2c->atomic_lock);
+	else
+		mutex_lock(&i2c->lock);
 
 	if (i2c->tx_msg || i2c->rx_msg) {
 		dev_err(i2c->adap.dev.parent,
@@ -1121,6 +1253,8 @@ static int xiic_start_xfer(struct xiic_i2c *i2c, struct i2c_msg *msgs, int num)
 		goto out;
 	}
 
+	i2c->atomic_xfer_state = STATE_DONE;
+
 	/* In single master mode bus can only be busy, when in use by this
 	 * driver. If the register indicates bus being busy for some reason we
 	 * should ignore it, since bus will never be released and i2c will be
@@ -1147,7 +1281,9 @@ static int xiic_start_xfer(struct xiic_i2c *i2c, struct i2c_msg *msgs, int num)
 	i2c->tx_msg = msgs;
 	i2c->rx_msg = NULL;
 	i2c->nmsgs = num;
-	init_completion(&i2c->completion);
+
+	if (!i2c->atomic)
+		init_completion(&i2c->completion);
 
 	/* Decide standard mode or Dynamic mode */
 	i2c->dynamic = true;
@@ -1182,7 +1318,10 @@ static int xiic_start_xfer(struct xiic_i2c *i2c, struct i2c_msg *msgs, int num)
 		__xiic_start_xfer(i2c);
 
 out:
-	mutex_unlock(&i2c->lock);
+	if (i2c->atomic)
+		spin_unlock(&i2c->atomic_lock);
+	else
+		mutex_unlock(&i2c->lock);
 
 	return ret;
 }
@@ -1221,6 +1360,44 @@ static int xiic_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
 	return err;
 }
 
+static int xiic_xfer_atomic(struct i2c_adapter *adap, struct i2c_msg *msgs, int num)
+{
+	struct xiic_i2c *i2c = i2c_get_adapdata(adap);
+	u32 status_reg;
+	int err;
+
+	err = xiic_i2c_runtime_resume(i2c->dev);
+	if (err)
+		return err;
+
+	i2c->atomic = true;
+	err = xiic_start_xfer(i2c, msgs, num);
+	if (err < 0)
+		return err;
+
+	err = readl_poll_timeout_atomic(i2c->base + XIIC_SR_REG_OFFSET,
+					status_reg, !(status_reg & XIIC_SR_BUS_BUSY_MASK),
+					1, XIIC_XFER_TIMEOUT_US);
+
+	if (err) /* Timeout */
+		err = -ETIMEDOUT;
+
+	spin_lock(&i2c->atomic_lock);
+	if (err || i2c->state) {
+		i2c->tx_msg = NULL;
+		i2c->rx_msg = NULL;
+		i2c->nmsgs = 0;
+	}
+
+	err = (i2c->atomic_xfer_state == STATE_DONE) ? num : -EIO;
+	spin_unlock(&i2c->atomic_lock);
+
+	i2c->atomic = false;
+	xiic_i2c_runtime_suspend(i2c->dev);
+
+	return err;
+}
+
 static u32 xiic_func(struct i2c_adapter *adap)
 {
 	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | I2C_FUNC_SMBUS_BLOCK_DATA;
@@ -1228,6 +1405,7 @@ static u32 xiic_func(struct i2c_adapter *adap)
 
 static const struct i2c_algorithm xiic_algorithm = {
 	.master_xfer = xiic_xfer,
+	.master_xfer_atomic = xiic_xfer_atomic,
 	.functionality = xiic_func,
 };
 
@@ -1291,6 +1469,7 @@ static int xiic_i2c_probe(struct platform_device *pdev)
 		 DRIVER_NAME " %s", pdev->name);
 
 	mutex_init(&i2c->lock);
+	spin_lock_init(&i2c->atomic_lock);
 
 	i2c->clk = devm_clk_get_enabled(&pdev->dev, NULL);
 	if (IS_ERR(i2c->clk))
-- 
2.34.1

Op 11-10-2024 om 12:41 schreef Manikanta Guntupalli:
> Rework the read and write code paths in the driver to support operation
> in atomic contexts.
>
> Similar changes have been implemented in other drivers, including:
> commit 3a5ee18d2a32 ("i2c: imx: implement master_xfer_atomic callback")
> commit 445094c8a9fb ("i2c: exynos5: add support for atomic transfers")
> commit ede2299f7101 ("i2c: tegra: Support atomic transfers")
> commit fe402bd09049 ("i2c: meson: implement the master_xfer_atomic
> callback")
>
> Signed-off-by: Manikanta Guntupalli <manikanta.guntupalli@amd.com>
> ---
>   drivers/i2c/busses/i2c-xiic.c | 245 +++++++++++++++++++++++++++++-----
>   1 file changed, 212 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/i2c/busses/i2c-xiic.c b/drivers/i2c/busses/i2c-xiic.c
> index 052bae4fc664..e5e9a4993bd4 100644
> --- a/drivers/i2c/busses/i2c-xiic.c
> +++ b/drivers/i2c/busses/i2c-xiic.c
> [...]
> +static void xiic_recv_atomic(struct xiic_i2c *i2c)
> +{
> +	while (xiic_rx_space(i2c)) {
Let's remind what xiic_rx_space is
#define xiic_rx_space(i2c) ((i2c)->rx_msg->len - (i2c)->rx_pos)

> +		if (xiic_getreg32(i2c, XIIC_IISR_OFFSET) & XIIC_INTR_RX_FULL_MASK) {
> +			if (!i2c->rx_msg) {
This check is suspicious. If i2c->rx_msg is NULL then the while
above already dereferenced a NULL pointer.
What is going on?
> [...]
> +}
> [...]
> +static void xiic_send_rem_atomic(struct xiic_i2c *i2c)
> +{
> +	if (!i2c->tx_msg)
> +		goto send_atomic_out;
> +	while (xiic_tx_space(i2c)) {
> [...]
> +	}
> +send_atomic_out:
> +	if (i2c->nmsgs > 1) {
> +		i2c->nmsgs--;
> +		i2c->tx_msg++;
We can get here with i2c->tx_msg being NULL. See the first if
in the function.
> +		__xiic_start_xfer(i2c);
> +	} else {
> +		xiic_irq_dis(i2c, XIIC_INTR_TX_HALF_MASK);
> +	}
>   }
> [...]

Hi Kees,

On Fri, Nov 22, 2024 at 10:29:27PM +0100, Kees Bakker wrote:
> Op 11-10-2024 om 12:41 schreef Manikanta Guntupalli:
> > Rework the read and write code paths in the driver to support operation
> > in atomic contexts.
> > 
> > Similar changes have been implemented in other drivers, including:
> > commit 3a5ee18d2a32 ("i2c: imx: implement master_xfer_atomic callback")
> > commit 445094c8a9fb ("i2c: exynos5: add support for atomic transfers")
> > commit ede2299f7101 ("i2c: tegra: Support atomic transfers")
> > commit fe402bd09049 ("i2c: meson: implement the master_xfer_atomic
> > callback")
> > 
> > Signed-off-by: Manikanta Guntupalli <manikanta.guntupalli@amd.com>
> > ---
> >   drivers/i2c/busses/i2c-xiic.c | 245 +++++++++++++++++++++++++++++-----
> >   1 file changed, 212 insertions(+), 33 deletions(-)
> > 
> > diff --git a/drivers/i2c/busses/i2c-xiic.c b/drivers/i2c/busses/i2c-xiic.c
> > index 052bae4fc664..e5e9a4993bd4 100644
> > --- a/drivers/i2c/busses/i2c-xiic.c
> > +++ b/drivers/i2c/busses/i2c-xiic.c
> > [...]
> > +static void xiic_recv_atomic(struct xiic_i2c *i2c)
> > +{
> > +	while (xiic_rx_space(i2c)) {
> Let's remind what xiic_rx_space is
> #define xiic_rx_space(i2c) ((i2c)->rx_msg->len - (i2c)->rx_pos)
> 
> > +		if (xiic_getreg32(i2c, XIIC_IISR_OFFSET) & XIIC_INTR_RX_FULL_MASK) {
> > +			if (!i2c->rx_msg) {
> This check is suspicious. If i2c->rx_msg is NULL then the while
> above already dereferenced a NULL pointer.
> What is going on?
> > [...]
> > +}
> > [...]
> > +static void xiic_send_rem_atomic(struct xiic_i2c *i2c)
> > +{
> > +	if (!i2c->tx_msg)
> > +		goto send_atomic_out;
> > +	while (xiic_tx_space(i2c)) {
> > [...]
> > +	}
> > +send_atomic_out:
> > +	if (i2c->nmsgs > 1) {
> > +		i2c->nmsgs--;
> > +		i2c->tx_msg++;
> We can get here with i2c->tx_msg being NULL. See the first if
> in the function.

Valid point. Thanks for looking into this and thanks Wolfram for
having removed it. I read this patch several times, but I missed
it.

Andi

> > +	while (xiic_rx_space(i2c)) {
> Let's remind what xiic_rx_space is
> #define xiic_rx_space(i2c) ((i2c)->rx_msg->len - (i2c)->rx_pos)
> 
> > +		if (xiic_getreg32(i2c, XIIC_IISR_OFFSET) & XIIC_INTR_RX_FULL_MASK) {
> > +			if (!i2c->rx_msg) {
> This check is suspicious. If i2c->rx_msg is NULL then the while
> above already dereferenced a NULL pointer.
> What is going on?

Valid point. I'll remove the patches from the pull request.