[PATCH v8 2/2] i2c: qcom-geni: Add dynamic transfer timeout based on transfer length and frequency

[Aniket Randive]

The driver uses a static XFER_TIMEOUT of HZ (1 second) for all transfers
regardless of message length or bus frequency, causing unnecessary
delays on error paths.

Use i2c_update_timeout() API to calculate transfer timeouts dynamically
based on message length and bus frequency. update the timeout per message
for FIFO, SE-DMA and GPI single descriptor transfers. For GPI multi
descriptor transfers, calculate the timeout from the combined length of
all messages, as completion is reported only after the entire batch has
finished.

A 10x safety margin over the theoretical wire time is applied, with a
300ms floor to account for I2C clock stretching and other situations where
a slave may keep SCL asserted for an extended period, including faulty
devices holding the bus.

Signed-off-by: Aniket Randive <aniket.randive@xxxxxxxxxxxxxxxx>
---
 drivers/i2c/busses/i2c-qcom-geni.c | 48 +++++++++++++++++++++++++++++++-------
 1 file changed, 39 insertions(+), 9 deletions(-)

diff --git a/drivers/i2c/busses/i2c-qcom-geni.c b/drivers/i2c/busses/i2c-qcom-geni.c
index 658636c1ee0e..203f4d627ca1 100644
--- a/drivers/i2c/busses/i2c-qcom-geni.c
+++ b/drivers/i2c/busses/i2c-qcom-geni.c
@@ -79,9 +79,14 @@ enum geni_i2c_err_code {
 
 #define ABORT_TIMEOUT		HZ
 #define CANCEL_TIMEOUT		HZ
-#define XFER_TIMEOUT		HZ
 #define RST_TIMEOUT		HZ
 
+/* 9 bits per byte (8 data + 1 ACK), 10x safety margin */
+#define I2C_TIMEOUT_SAFETY_COEFFICIENT	10
+
+/* 300ms floor: budget for clock stretching; slave may hold SCL low indefinitely */
+#define I2C_TIMEOUT_MIN_USEC		300000
+
 struct geni_i2c_desc {
 	bool no_dma_support;
 	unsigned int tx_fifo_depth;
@@ -513,7 +518,10 @@ static int geni_i2c_rx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
 	}
 
 	cur = gi2c->cur;
-	time_left = wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT);
+	i2c_update_timeout(&gi2c->adap, gi2c->clk_freq_out, len,
+			   I2C_TIMEOUT_SAFETY_COEFFICIENT,
+			   I2C_TIMEOUT_MIN_USEC);
+	time_left = wait_for_completion_timeout(&gi2c->done, gi2c->adap.timeout);
 	if (!time_left || (gi2c->err && gi2c->err != gi2c_log[ADDR_NACK].err))
 		geni_i2c_cancel_xfer(gi2c);
 
@@ -555,7 +563,10 @@ static int geni_i2c_tx_one_msg(struct geni_i2c_dev *gi2c, struct i2c_msg *msg,
 		writel_relaxed(1, se->base + SE_GENI_TX_WATERMARK_REG);
 
 	cur = gi2c->cur;
-	time_left = wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT);
+	i2c_update_timeout(&gi2c->adap, gi2c->clk_freq_out, len,
+			   I2C_TIMEOUT_SAFETY_COEFFICIENT,
+			   I2C_TIMEOUT_MIN_USEC);
+	time_left = wait_for_completion_timeout(&gi2c->done, gi2c->adap.timeout);
 	if (!time_left || (gi2c->err && gi2c->err != gi2c_log[ADDR_NACK].err))
 		geni_i2c_cancel_xfer(gi2c);
 
@@ -633,7 +644,7 @@ static void geni_i2c_gpi_multi_desc_unmap(struct geni_i2c_dev *gi2c, struct i2c_
  * geni_i2c_gpi_multi_xfer_timeout_handler() - Handles multi message transfer timeout
  * @dev: Pointer to the corresponding dev node
  * @multi_xfer: Pointer to the geni_i2c_gpi_multi_desc_xfer
- * @transfer_timeout_msecs: Timeout value in milliseconds
+ * @timeout_jiffies: Per-message completion timeout in jiffies
  * @transfer_comp: Completion object of the transfer
  *
  * This function waits for the completion of each processed transfer messages
@@ -643,18 +654,18 @@ static void geni_i2c_gpi_multi_desc_unmap(struct geni_i2c_dev *gi2c, struct i2c_
  */
 static int geni_i2c_gpi_multi_xfer_timeout_handler(struct device *dev,
 						   struct geni_i2c_gpi_multi_desc_xfer *multi_xfer,
-						   u32 transfer_timeout_msecs,
+						   unsigned long timeout_jiffies,
 						   struct completion *transfer_comp)
 {
 	int i;
-	u32 time_left;
+	unsigned long time_left;
 
 	for (i = 0; i < multi_xfer->msg_idx_cnt - 1; i++) {
 		reinit_completion(transfer_comp);
 
 		if (multi_xfer->msg_idx_cnt != multi_xfer->irq_cnt) {
 			time_left = wait_for_completion_timeout(transfer_comp,
-								transfer_timeout_msecs);
+								timeout_jiffies);
 			if (!time_left) {
 				dev_err(dev, "%s: Transfer timeout\n", __func__);
 				return -ETIMEDOUT;
@@ -778,8 +789,24 @@ static int geni_i2c_gpi(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[],
 		dma_async_issue_pending(gi2c->tx_c);
 
 		if ((msg_idx == (gi2c->num_msgs - 1)) || flags & DMA_PREP_INTERRUPT) {
+			size_t total_len = 0;
+			int j;
+
+			/*
+			 * All TREs except the last carry the BEI bit, so a single
+			 * completion interrupt fires only after the entire batch has
+			 * drained on the wire. The timeout budget must therefore cover
+			 * the combined wire time of every message in the batch.
+			 */
+			for (j = 0; j < gi2c->num_msgs; j++)
+				total_len += msgs[j].len;
+
+			i2c_update_timeout(&gi2c->adap, gi2c->clk_freq_out, total_len,
+					   I2C_TIMEOUT_SAFETY_COEFFICIENT,
+					   I2C_TIMEOUT_MIN_USEC);
 			ret = geni_i2c_gpi_multi_xfer_timeout_handler(gi2c->se.dev, gi2c_gpi_xfer,
-								      XFER_TIMEOUT, &gi2c->done);
+								      gi2c->adap.timeout,
+								      &gi2c->done);
 			if (ret) {
 				dev_err(gi2c->se.dev,
 					"I2C multi write msg transfer timeout: %d\n",
@@ -899,7 +926,10 @@ static int geni_i2c_gpi_xfer(struct geni_i2c_dev *gi2c, struct i2c_msg msgs[], i
 
 		if (!gi2c->is_tx_multi_desc_xfer) {
 			dma_async_issue_pending(gi2c->tx_c);
-			time_left = wait_for_completion_timeout(&gi2c->done, XFER_TIMEOUT);
+			i2c_update_timeout(&gi2c->adap, gi2c->clk_freq_out, msgs[i].len,
+					   I2C_TIMEOUT_SAFETY_COEFFICIENT,
+					   I2C_TIMEOUT_MIN_USEC);
+			time_left = wait_for_completion_timeout(&gi2c->done, gi2c->adap.timeout);
 			if (!time_left) {
 				dev_err(gi2c->se.dev, "%s:I2C timeout\n", __func__);
 				gi2c->err = -ETIMEDOUT;

-- 
2.34.1