recipes-kernel/linux/files/0001-mctp-i2c-add-MCTP-retry-mechanism.patch

From 9e2ff138c053f809c1d994d4d013ef8c35bddc89 Mon Sep 17 00:00:00 2001
From: Jinliang Wang <jinliangw@google.com>
Date: Mon, 22 Apr 2024 15:50:24 -0700
Subject: [PATCH] mctp-i2c: add MCTP retry mechanism

In include/uapi/linux/i2c.h, define two new flags for i2c_msg.flags:
I2C_M_IS_MCTP and I2C_M_LAST_RETRY.
In mctp-i2c.c, add mctp_i2c_transfer_with_retry function
which will perform TX mctp packet retry logic, approximately
20 ms x 100 times = 2 seconds.

Patch Tracking Bug: b/335839424
Upstream info / review: N/A
Upstream-Status: Pending
Justification: Need to solve the MCTP retry and recover issues

Google-Bug-Id: 286397121
Signed-off-by: Jinliang Wang <jinliangw@google.com>
---
 drivers/net/mctp/mctp-i2c.c | 40 +++++++++++++++++++++++++++++++++++--
 include/uapi/linux/i2c.h    |  2 ++
 2 files changed, 40 insertions(+), 2 deletions(-)

diff --git a/drivers/net/mctp/mctp-i2c.c b/drivers/net/mctp/mctp-i2c.c
index baf7afac7857..820e6f61b7f9 100644
--- a/drivers/net/mctp/mctp-i2c.c
+++ b/drivers/net/mctp/mctp-i2c.c
@@ -435,6 +435,42 @@ static void mctp_i2c_unlock_reset(struct mctp_i2c_dev *midev)
 		i2c_unlock_bus(midev->adapter, I2C_LOCK_SEGMENT);
 }
 
+#define RETRY_TIME_MS 2000
+#define RETRY_INVERVAL_MS 20
+#define RETRY_CNT (RETRY_TIME_MS / RETRY_INVERVAL_MS)
+#define ENXIO_RETRY_LIMIT 5
+
+static int mctp_i2c_transfer_with_retry(struct i2c_adapter *adap,
+					struct i2c_msg *msg)
+{
+	int rc = 0;
+	int retry = 0; /* General retry count */
+	int enxio_retry = 0; /* Special retry count for ENXIO error */
+	msg->flags = I2C_M_IS_MCTP;
+	while (retry < RETRY_CNT) {
+		retry++;
+		rc = __i2c_transfer(adap, msg, 1);
+		if (rc == -ENXIO) {
+			enxio_retry++;
+			if (enxio_retry >= ENXIO_RETRY_LIMIT) {
+				/* Jump out if we accumulate enough ENXIO error */
+				break;
+			}
+		} else if (rc == -EBUSY || rc == -EAGAIN || rc == -EPROTO) {
+			if (retry >= (RETRY_CNT - 1)) {
+				/* Set last retry flag so i2c driver layer may perform necessary recovery */
+				msg->flags |= I2C_M_LAST_RETRY;
+			}
+		} else {
+			break;
+		}
+		msleep_interruptible(RETRY_INVERVAL_MS);
+		/* Continue to retry */
+	}
+
+	return rc;
+}
+
 static void mctp_i2c_xmit(struct mctp_i2c_dev *midev, struct sk_buff *skb)
 {
 	struct net_device_stats *stats = &midev->ndev->stats;
@@ -478,7 +514,7 @@ static void mctp_i2c_xmit(struct mctp_i2c_dev *midev, struct sk_buff *skb)
 		/* no flow: full lock & unlock */
 		mctp_i2c_lock_nest(midev);
 		mctp_i2c_device_select(midev->client, midev);
-		rc = __i2c_transfer(midev->adapter, &msg, 1);
+		rc = mctp_i2c_transfer_with_retry(midev->adapter, &msg);
 		mctp_i2c_unlock_nest(midev);
 		break;
 
@@ -492,7 +528,7 @@ static void mctp_i2c_xmit(struct mctp_i2c_dev *midev, struct sk_buff *skb)
 
 	case MCTP_I2C_TX_FLOW_EXISTING:
 		/* existing flow: we already have the lock; just tx */
-		rc = __i2c_transfer(midev->adapter, &msg, 1);
+		rc = mctp_i2c_transfer_with_retry(midev->adapter, &msg);
 		break;
 
 	case MCTP_I2C_TX_FLOW_INVALID:
diff --git a/include/uapi/linux/i2c.h b/include/uapi/linux/i2c.h
index 92326ebde350..c77b74501b05 100644
--- a/include/uapi/linux/i2c.h
+++ b/include/uapi/linux/i2c.h
@@ -75,6 +75,8 @@ struct i2c_msg {
 	__u16 flags;
 #define I2C_M_RD		0x0001	/* guaranteed to be 0x0001! */
 #define I2C_M_TEN		0x0010	/* use only if I2C_FUNC_10BIT_ADDR */
+#define I2C_M_IS_MCTP		0x0020  /* use only if msg is MCTP over i2c binding */
+#define I2C_M_LAST_RETRY	0x0040  /* use only if msg is the last retry of a message */
 #define I2C_M_DMA_SAFE		0x0200	/* use only in kernel space */
 #define I2C_M_RECV_LEN		0x0400	/* use only if I2C_FUNC_SMBUS_READ_BLOCK_DATA */
 #define I2C_M_NO_RD_ACK		0x0800	/* use only if I2C_FUNC_PROTOCOL_MANGLING */
-- 
2.44.0.769.g3c40516874-goog