Thread (4 messages) 4 messages, 2 authors, 2025-07-23

[PATCH v5 1/2] i2c: lpi2c: use readl_poll_timeout() for register polling

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From: Francesco Dolcini <francesco@dolcini.it>
Date: 2025-07-18 13:43:01
Also in: imx, linux-i2c, lkml
Subsystem: freescale imx lpi2c driver, i2c subsystem, i2c subsystem host drivers, the rest · Maintainers: Dong Aisheng, Andi Shyti, Linus Torvalds

Revision v5 of 2 in this series; 2 review trailers; landed in mainline as 8336f9de21f7 on 2025-07-25.

Revisions (2)
  1. v4 [diff vs current]
  2. v5 current 
From: Emanuele Ghidoli <redacted>

Replaces polling loops with the readl_poll_timeout() helper macro.

Signed-off-by: Emanuele Ghidoli <redacted>
Signed-off-by: Francesco Dolcini <redacted>
Reviewed-by: Carlos Song <redacted>
Tested-by: Primoz Fiser <redacted>
---
v4 -> v5
- rebased due to commit 614b1c3cbfb0 ("i2c: use inclusive callbacks in struct i2c_algorithm").
- add Tested-by Primoz

v3 -> v4
- Split the patch into two parts: one for the readl_poll_timeout() and one for the atomic implementation.
- Change the readl_poll_timeout() delay to 0 us to do not change the behavior of the driver.
- Use err variable consistently.

v2 -> v3
- Closes: https://lore.kernel.org/oe-kbuild-all/202505130735.zh3WuTNu-lkp@intel.com/ (local). Using the return value of
lpi2c_imx_read_msr_poll_timeout() to check for errors.

v1 -> v2
- Rename READL_POLL_TIMEOUT to lpi2c_imx_read_msr_poll_timeout
- Remove addr and timeout_us parameters from lpi2c_imx_read_msr_poll_timeout since they are used always with the same value
- add r-b tag from Carlos Song
---
 drivers/i2c/busses/i2c-imx-lpi2c.c | 94 ++++++++++++++----------------
 1 file changed, 45 insertions(+), 49 deletions(-)

diff --git a/drivers/i2c/busses/i2c-imx-lpi2c.c b/drivers/i2c/busses/i2c-imx-lpi2c.c
index 064bc83840a6..4a25c92adfc1 100644
--- a/drivers/i2c/busses/i2c-imx-lpi2c.c
+++ b/drivers/i2c/busses/i2c-imx-lpi2c.c
@@ -16,6 +16,7 @@
 #include <linux/init.h>
 #include <linux/interrupt.h>
 #include <linux/io.h>
+#include <linux/iopoll.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/of.h>
@@ -187,6 +188,10 @@ struct lpi2c_imx_struct {
 	struct i2c_client	*target;
 };
 
+#define lpi2c_imx_read_msr_poll_timeout(val, cond)                            \
+		  readl_poll_timeout(lpi2c_imx->base + LPI2C_MSR, val, cond,  \
+				     0, 500000)
+
 static void lpi2c_imx_intctrl(struct lpi2c_imx_struct *lpi2c_imx,
 			      unsigned int enable)
 {
@@ -195,33 +200,34 @@ static void lpi2c_imx_intctrl(struct lpi2c_imx_struct *lpi2c_imx,
 
 static int lpi2c_imx_bus_busy(struct lpi2c_imx_struct *lpi2c_imx)
 {
-	unsigned long orig_jiffies = jiffies;
+	int err;
 	unsigned int temp;
 
-	while (1) {
-		temp = readl(lpi2c_imx->base + LPI2C_MSR);
-
-		/* check for arbitration lost, clear if set */
-		if (temp & MSR_ALF) {
-			writel(temp, lpi2c_imx->base + LPI2C_MSR);
-			return -EAGAIN;
-		}
+	err = lpi2c_imx_read_msr_poll_timeout(temp,
+					      temp & (MSR_ALF | MSR_BBF | MSR_MBF));
 
-		if (temp & (MSR_BBF | MSR_MBF))
-			break;
+	/* check for arbitration lost, clear if set */
+	if (temp & MSR_ALF) {
+		writel(temp, lpi2c_imx->base + LPI2C_MSR);
+		return -EAGAIN;
+	}
 
-		if (time_after(jiffies, orig_jiffies + msecs_to_jiffies(500))) {
-			dev_dbg(&lpi2c_imx->adapter.dev, "bus not work\n");
-			if (lpi2c_imx->adapter.bus_recovery_info)
-				i2c_recover_bus(&lpi2c_imx->adapter);
-			return -ETIMEDOUT;
-		}
-		schedule();
+	/* check for bus not busy */
+	if (err) {
+		dev_dbg(&lpi2c_imx->adapter.dev, "bus not work\n");
+		if (lpi2c_imx->adapter.bus_recovery_info)
+			i2c_recover_bus(&lpi2c_imx->adapter);
+		return -ETIMEDOUT;
 	}
 
 	return 0;
 }
 
+static u32 lpi2c_imx_txfifo_cnt(struct lpi2c_imx_struct *lpi2c_imx)
+{
+	return readl(lpi2c_imx->base + LPI2C_MFSR) & 0xff;
+}
+
 static void lpi2c_imx_set_mode(struct lpi2c_imx_struct *lpi2c_imx)
 {
 	unsigned int bitrate = lpi2c_imx->bitrate;
@@ -259,25 +265,18 @@ static int lpi2c_imx_start(struct lpi2c_imx_struct *lpi2c_imx,
 
 static void lpi2c_imx_stop(struct lpi2c_imx_struct *lpi2c_imx)
 {
-	unsigned long orig_jiffies = jiffies;
 	unsigned int temp;
+	int err;
 
 	writel(GEN_STOP << 8, lpi2c_imx->base + LPI2C_MTDR);
 
-	do {
-		temp = readl(lpi2c_imx->base + LPI2C_MSR);
-		if (temp & MSR_SDF)
-			break;
+	err = lpi2c_imx_read_msr_poll_timeout(temp, temp & MSR_SDF);
 
-		if (time_after(jiffies, orig_jiffies + msecs_to_jiffies(500))) {
-			dev_dbg(&lpi2c_imx->adapter.dev, "stop timeout\n");
-			if (lpi2c_imx->adapter.bus_recovery_info)
-				i2c_recover_bus(&lpi2c_imx->adapter);
-			break;
-		}
-		schedule();
-
-	} while (1);
+	if (err) {
+		dev_dbg(&lpi2c_imx->adapter.dev, "stop timeout\n");
+		if (lpi2c_imx->adapter.bus_recovery_info)
+			i2c_recover_bus(&lpi2c_imx->adapter);
+	}
 }
 
 /* CLKLO = I2C_CLK_RATIO * CLKHI, SETHOLD = CLKHI, DATAVD = CLKHI/2 */
@@ -393,26 +392,23 @@ static int lpi2c_imx_pio_msg_complete(struct lpi2c_imx_struct *lpi2c_imx)
 
 static int lpi2c_imx_txfifo_empty(struct lpi2c_imx_struct *lpi2c_imx)
 {
-	unsigned long orig_jiffies = jiffies;
-	u32 txcnt;
-
-	do {
-		txcnt = readl(lpi2c_imx->base + LPI2C_MFSR) & 0xff;
+	unsigned int temp;
+	int err;
 
-		if (readl(lpi2c_imx->base + LPI2C_MSR) & MSR_NDF) {
-			dev_dbg(&lpi2c_imx->adapter.dev, "NDF detected\n");
-			return -EIO;
-		}
+	err = lpi2c_imx_read_msr_poll_timeout(temp,
+					      (temp & MSR_NDF) || !lpi2c_imx_txfifo_cnt(lpi2c_imx));
 
-		if (time_after(jiffies, orig_jiffies + msecs_to_jiffies(500))) {
-			dev_dbg(&lpi2c_imx->adapter.dev, "txfifo empty timeout\n");
-			if (lpi2c_imx->adapter.bus_recovery_info)
-				i2c_recover_bus(&lpi2c_imx->adapter);
-			return -ETIMEDOUT;
-		}
-		schedule();
+	if (temp & MSR_NDF) {
+		dev_dbg(&lpi2c_imx->adapter.dev, "NDF detected\n");
+		return -EIO;
+	}
 
-	} while (txcnt);
+	if (err) {
+		dev_dbg(&lpi2c_imx->adapter.dev, "txfifo empty timeout\n");
+		if (lpi2c_imx->adapter.bus_recovery_info)
+			i2c_recover_bus(&lpi2c_imx->adapter);
+		return -ETIMEDOUT;
+	}
 
 	return 0;
 }
-- 
2.39.5
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