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FAILED: patch "[PATCH] i2c: imx: fix locked bus on SMBus block-read of 0 (atomic)" failed to apply to 6.12-stable tree

PATCH New [email protected] 2 participants 3 messages Jul 20 – Jul 27

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Stable branch Arm i.MX and Layerscape I2C subsystem host drivers Freescale i.MX I2C driver
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#0 lore raw

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x cb2fc37857693b55909fb77dc2c87cfbc1cdc476
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026072035-flight-slacker-b884@gregkh' --subject-prefix 'PATCH 6.12.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From cb2fc37857693b55909fb77dc2c87cfbc1cdc476 Mon Sep 17 00:00:00 2001
From: Vincent Jardin <[email protected]>
Date: Mon, 13 Jul 2026 20:11:59 +0200
Subject: [PATCH] i2c: imx: fix locked bus on SMBus block-read of 0 (atomic)

SMBus 3.1 6.5.7 allows a Block Read byte count of 0, but the atomic (polling) path rejects it as -EPROTO. Worse, it returns without a NACK+STOP: the next receive cycle has already started, so the target keeps holding SDA and the bus stays stuck until a power cycle for this i2c controller.

Reading I2DR to obtain the count likewise arms the next byte on the count > I2C_SMBUS_BLOCK_MAX path, which also returned -EPROTO directly and left the bus held.

Handle both: NACK the in-flight dummy byte (TXAK) and extend msgs->len so the existing last-byte handling emits STOP; the dummy byte is discarded. A count of 0 is a valid empty block read; a count above I2C_SMBUS_BLOCK_MAX is still reported as -EPROTO, but only after the bus has been released.

The interrupt-driven path has the same flaw from a later commit and is fixed separately, as it carries a different Fixes: tag and stable range.

Fixes 8e8782c71595 ("i2c: imx: add SMBus block read support")
Signed-off-by Vincent Jardin <[email protected]>
Cc <[email protected]> # v3.16+
Acked-by Oleksij Rempel <[email protected]>
Acked-by Carlos Song <[email protected]>
Reviewed-by Stefan Eichenberger <[email protected]>
Signed-off-by Andi Shyti <[email protected]>
Link https://lore.kernel.org/r/20260713-for-upstream-i2c-lx2160-fix-v1-v3-1-073ac9e103a5@free.fr open here
drivers/i2c/busses/i2c-imx.c +16 -3
index 28313d0fad37..cfd1e63359e7 100644
@@ -1415,6 +1415,7 @@ static int i2c_imx_atomic_read(struct imx_i2c_struct *i2c_imx,
 	int i, result;
 	unsigned int temp;
 	int block_data = msgs->flags & I2C_M_RECV_LEN;
+	int block_err = 0;
 
 	result = i2c_imx_prepare_read(i2c_imx, msgs, false);
 	if (result)

@@ -1436,8 +1437,20 @@ static int i2c_imx_atomic_read(struct imx_i2c_struct *i2c_imx,
 		 */
 		if ((!i) && block_data) {
 			len = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR);
-			if ((len == 0) || (len > I2C_SMBUS_BLOCK_MAX))
-				return -EPROTO;
+			if ((len == 0) || (len > I2C_SMBUS_BLOCK_MAX)) {
+				/*
+				 * SMBus 3.1 6.5.7: support count byte of 0.
+				 * I2C_SMBUS_BLOCK_MAX case should not hold the SDA either.
+				 */
+				if (len > I2C_SMBUS_BLOCK_MAX)
+					block_err = -EPROTO;
+				temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
+				temp |= I2CR_TXAK;
+				imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
+				msgs->buf[0] = 0;
+				msgs->len = 2;
+				continue;
+			}
 			dev_dbg(&i2c_imx->adapter.dev,
 				"<%s> read length: 0x%X\n",
 				__func__, len);

@@ -1485,7 +1498,7 @@ static int i2c_imx_atomic_read(struct imx_i2c_struct *i2c_imx,
 			"<%s> read byte: B%d=0x%X\n",
 			__func__, i, msgs->buf[i]);
 	}
-	return 0;
+	return block_err;
 }
 
 static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs,
maintainer
#1 lore raw

PATCH 1/2 i2c: imx: separate atomic, dma and non-dma use case

From: Stefan Eichenberger <[email protected]>

[ Upstream commit b460b15b3cc23ef3639cc51043bf8b2a70ca1878 ]

Separate the atomic, dma and non-dma use case as a preparation step for moving the non-dma use case to the isr to avoid rescheduling while a transfer is in progress.

Signed-off-by Stefan Eichenberger <[email protected]>
Reviewed-by Frank Li <[email protected]>
Acked-by Oleksij Rempel <[email protected]>
Signed-off-by Andi Shyti <[email protected]>

Stable-dep-of: cb2fc3785769 ("i2c: imx: fix locked bus on SMBus block-read of 0 (atomic)")

Signed-off-by Sasha Levin <[email protected]>
---
 drivers/i2c/busses/i2c-imx.c | 107 +++++++++++++++++++++++------------
 1 file changed, 70 insertions(+), 37 deletions(-)
drivers/i2c/busses/i2c-imx.c +70 -37
index c5224d43eea45e..7c27d790a94882 100644
@@ -1007,6 +1007,43 @@ static int i2c_imx_dma_write(struct imx_i2c_struct *i2c_imx,
 	return i2c_imx_acked(i2c_imx);
 }
 
+static int i2c_imx_prepare_read(struct imx_i2c_struct *i2c_imx,
+				struct i2c_msg *msgs, bool atomic,
+				bool use_dma)
+{
+	int result;
+	unsigned int temp = 0;
+
+	/* write slave address */
+	imx_i2c_write_reg(i2c_8bit_addr_from_msg(msgs), i2c_imx, IMX_I2C_I2DR);
+	result = i2c_imx_trx_complete(i2c_imx, atomic);
+	if (result)
+		return result;
+	result = i2c_imx_acked(i2c_imx);
+	if (result)
+		return result;
+
+	dev_dbg(&i2c_imx->adapter.dev, "<%s> setup bus\n", __func__);
+
+	/* setup bus to read data */
+	temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
+	temp &= ~I2CR_MTX;
+
+	/*
+	 * Reset the I2CR_TXAK flag initially for SMBus block read since the
+	 * length is unknown
+	 */
+	if (msgs->len - 1)
+		temp &= ~I2CR_TXAK;
+	if (use_dma)
+		temp |= I2CR_DMAEN;
+
+	imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
+	imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR); /* dummy read */
+
+	return 0;
+}
+
 static int i2c_imx_dma_read(struct imx_i2c_struct *i2c_imx,
 			struct i2c_msg *msgs, bool is_lastmsg)
 {

@@ -1017,6 +1054,11 @@ static int i2c_imx_dma_read(struct imx_i2c_struct *i2c_imx,
 	struct imx_i2c_dma *dma = i2c_imx->dma;
 	struct device *dev = &i2c_imx->adapter.dev;
 
+	result = i2c_imx_prepare_read(i2c_imx, msgs, false, true);
+	if (result)
+		return result;
+
+	dev_dbg(&i2c_imx->adapter.dev, "<%s> read data\n", __func__);
 
 	dma->chan_using = dma->chan_rx;
 	dma->dma_transfer_dir = DMA_DEV_TO_MEM;

@@ -1127,50 +1169,24 @@ static int i2c_imx_write(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs,
 	return 0;
 }
 
+static int i2c_imx_atomic_write(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs)
+{
+	return i2c_imx_write(i2c_imx, msgs, true);
+}
+
 static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs,
 			bool is_lastmsg, bool atomic)
 {
 	int i, result;
 	unsigned int temp;
 	int block_data = msgs->flags & I2C_M_RECV_LEN;
-	int use_dma = i2c_imx->dma && msgs->flags & I2C_M_DMA_SAFE &&
-		msgs->len >= DMA_THRESHOLD && !block_data;
 
-	dev_dbg(&i2c_imx->adapter.dev,
-		"<%s> write slave address: addr=0x%x\n",
-		__func__, i2c_8bit_addr_from_msg(msgs));
-
-	/* write slave address */
-	imx_i2c_write_reg(i2c_8bit_addr_from_msg(msgs), i2c_imx, IMX_I2C_I2DR);
-	result = i2c_imx_trx_complete(i2c_imx, atomic);
+	result = i2c_imx_prepare_read(i2c_imx, msgs, atomic, false);
 	if (result)
 		return result;
-	result = i2c_imx_acked(i2c_imx);
-	if (result)
-		return result;
-
-	dev_dbg(&i2c_imx->adapter.dev, "<%s> setup bus\n", __func__);
-
-	/* setup bus to read data */
-	temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
-	temp &= ~I2CR_MTX;
-
-	/*
-	 * Reset the I2CR_TXAK flag initially for SMBus block read since the
-	 * length is unknown
-	 */
-	if ((msgs->len - 1) || block_data)
-		temp &= ~I2CR_TXAK;
-	if (use_dma)
-		temp |= I2CR_DMAEN;
-	imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
-	imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR); /* dummy read */
 
 	dev_dbg(&i2c_imx->adapter.dev, "<%s> read data\n", __func__);
 
-	if (use_dma)
-		return i2c_imx_dma_read(i2c_imx, msgs, is_lastmsg);
-
 	/* read data */
 	for (i = 0; i < msgs->len; i++) {
 		u8 len = 0;

@@ -1237,6 +1253,12 @@ static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs,
 	return 0;
 }
 
+static int i2c_imx_atomic_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs,
+			       bool is_lastmsg)
+{
+	return i2c_imx_read(i2c_imx, msgs, is_lastmsg, true);
+}
+
 static int i2c_imx_xfer_common(struct i2c_adapter *adapter,
 			       struct i2c_msg *msgs, int num, bool atomic)
 {

@@ -1244,6 +1266,7 @@ static int i2c_imx_xfer_common(struct i2c_adapter *adapter,
 	int result;
 	bool is_lastmsg = false;
 	struct imx_i2c_struct *i2c_imx = i2c_get_adapdata(adapter);
+	int use_dma = 0;
 
 	/* Start I2C transfer */
 	result = i2c_imx_start(i2c_imx, atomic);

@@ -1296,15 +1319,25 @@ static int i2c_imx_xfer_common(struct i2c_adapter *adapter,
 			(temp & I2SR_SRW ? 1 : 0), (temp & I2SR_IIF ? 1 : 0),
 			(temp & I2SR_RXAK ? 1 : 0));
 #endif
+
+		use_dma = i2c_imx->dma && msgs[i].len >= DMA_THRESHOLD &&
+			msgs[i].flags & I2C_M_DMA_SAFE;
 		if (msgs[i].flags & I2C_M_RD) {
-			result = i2c_imx_read(i2c_imx, &msgs[i], is_lastmsg, atomic);
+			int block_data = msgs->flags & I2C_M_RECV_LEN;
+
+			if (atomic)
+				result = i2c_imx_atomic_read(i2c_imx, &msgs[i], is_lastmsg);
+			else if (use_dma && !block_data)
+				result = i2c_imx_dma_read(i2c_imx, &msgs[i], is_lastmsg);
+			else
+				result = i2c_imx_read(i2c_imx, &msgs[i], is_lastmsg, false);
 		} else {
-			if (!atomic &&
-			    i2c_imx->dma && msgs[i].len >= DMA_THRESHOLD &&
-				msgs[i].flags & I2C_M_DMA_SAFE)
+			if (atomic)
+				result = i2c_imx_atomic_write(i2c_imx, &msgs[i]);
+			else if (use_dma)
 				result = i2c_imx_dma_write(i2c_imx, &msgs[i]);
 			else
-				result = i2c_imx_write(i2c_imx, &msgs[i], atomic);
+				result = i2c_imx_write(i2c_imx, &msgs[i], false);
 		}
 		if (result)
 			goto fail0;
Signature · 1 line
2.53.0
maintainer
#2 lore raw

PATCH 2/2 i2c: imx: fix locked bus on SMBus block-read of 0 (atomic)

From: Vincent Jardin <[email protected]>

[ Upstream commit cb2fc37857693b55909fb77dc2c87cfbc1cdc476 ]

SMBus 3.1 6.5.7 allows a Block Read byte count of 0, but the atomic (polling) path rejects it as -EPROTO. Worse, it returns without a NACK+STOP: the next receive cycle has already started, so the target keeps holding SDA and the bus stays stuck until a power cycle for this i2c controller.

Reading I2DR to obtain the count likewise arms the next byte on the count > I2C_SMBUS_BLOCK_MAX path, which also returned -EPROTO directly and left the bus held.

Handle both: NACK the in-flight dummy byte (TXAK) and extend msgs->len so the existing last-byte handling emits STOP; the dummy byte is discarded. A count of 0 is a valid empty block read; a count above I2C_SMBUS_BLOCK_MAX is still reported as -EPROTO, but only after the bus has been released.

The interrupt-driven path has the same flaw from a later commit and is fixed separately, as it carries a different Fixes: tag and stable range.

Fixes 8e8782c71595 ("i2c: imx: add SMBus block read support")
Signed-off-by Vincent Jardin <[email protected]>
Cc <[email protected]> # v3.16+
Acked-by Oleksij Rempel <[email protected]>
Acked-by Carlos Song <[email protected]>
Reviewed-by Stefan Eichenberger <[email protected]>
Signed-off-by Andi Shyti <[email protected]>
Link https://lore.kernel.org/r/20260713-for-upstream-i2c-lx2160-fix-v1-v3-1-073ac9e103a5@free.fr open here
Signed-off-by Sasha Levin <[email protected]>
---
 drivers/i2c/busses/i2c-imx.c | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)
drivers/i2c/busses/i2c-imx.c +16 -3
index 7c27d790a94882..45e71120fdc146 100644
@@ -1180,6 +1180,7 @@ static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs,
 	int i, result;
 	unsigned int temp;
 	int block_data = msgs->flags & I2C_M_RECV_LEN;
+	int block_err = 0;
 
 	result = i2c_imx_prepare_read(i2c_imx, msgs, atomic, false);
 	if (result)

@@ -1201,8 +1202,20 @@ static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs,
 		 */
 		if ((!i) && block_data) {
 			len = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2DR);
-			if ((len == 0) || (len > I2C_SMBUS_BLOCK_MAX))
-				return -EPROTO;
+			if ((len == 0) || (len > I2C_SMBUS_BLOCK_MAX)) {
+				/*
+				 * SMBus 3.1 6.5.7: support count byte of 0.
+				 * I2C_SMBUS_BLOCK_MAX case should not hold the SDA either.
+				 */
+				if (len > I2C_SMBUS_BLOCK_MAX)
+					block_err = -EPROTO;
+				temp = imx_i2c_read_reg(i2c_imx, IMX_I2C_I2CR);
+				temp |= I2CR_TXAK;
+				imx_i2c_write_reg(temp, i2c_imx, IMX_I2C_I2CR);
+				msgs->buf[0] = 0;
+				msgs->len = 2;
+				continue;
+			}
 			dev_dbg(&i2c_imx->adapter.dev,
 				"<%s> read length: 0x%X\n",
 				__func__, len);

@@ -1250,7 +1263,7 @@ static int i2c_imx_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs,
 			"<%s> read byte: B%d=0x%X\n",
 			__func__, i, msgs->buf[i]);
 	}
-	return 0;
+	return block_err;
 }
 
 static int i2c_imx_atomic_read(struct imx_i2c_struct *i2c_imx, struct i2c_msg *msgs,
Signature · 1 line
2.53.0