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From:   "William A. Kennington III" <william@wkennington.com>
To:     tmaimon77@gmail.com, tali.perry1@gmail.com, avifishman70@gmail.com,
        wsa@kernel.org, joel@jms.id.au
Cc:     linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org,
        "William A. Kennington III" <william@wkennington.com>
Subject: [PATCH] i2c: npcm7xx: Fix callback completion ordering
Date:   Sat, 23 Sep 2023 18:02:14 -0700
Message-ID: <20230924010214.3700150-1-william@wkennington.com>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

Sometimes, our completions race with new master transfers and override
the bus->operation and bus->master_or_slave variables. This causes
transactions to timeout and kernel crashes less frequently.

To remedy this, we re-order all completions to the very end of the
function.

Fixes: 56a1485b102e ("i2c: npcm7xx: Add Nuvoton NPCM I2C controller driver")
Signed-off-by: William A. Kennington III <william@wkennington.com>
---
 drivers/i2c/busses/i2c-npcm7xx.c | 17 +++++++----------
 1 file changed, 7 insertions(+), 10 deletions(-)

diff --git a/drivers/i2c/busses/i2c-npcm7xx.c b/drivers/i2c/busses/i2c-npcm7xx.c
index 495a8b5f6a2b..ae4bae63ad4f 100644
--- a/drivers/i2c/busses/i2c-npcm7xx.c
+++ b/drivers/i2c/busses/i2c-npcm7xx.c
@@ -694,6 +694,7 @@ static void npcm_i2c_callback(struct npcm_i2c *bus,
 {
 	struct i2c_msg *msgs;
 	int msgs_num;
+	bool do_complete = false;
 
 	msgs = bus->msgs;
 	msgs_num = bus->msgs_num;
@@ -722,23 +723,17 @@ static void npcm_i2c_callback(struct npcm_i2c *bus,
 				 msgs[1].flags & I2C_M_RD)
 				msgs[1].len = info;
 		}
-		if (completion_done(&bus->cmd_complete) == false)
-			complete(&bus->cmd_complete);
-	break;
-
+		do_complete = true;
+		break;
 	case I2C_NACK_IND:
 		/* MASTER transmit got a NACK before tx all bytes */
 		bus->cmd_err = -ENXIO;
-		if (bus->master_or_slave == I2C_MASTER)
-			complete(&bus->cmd_complete);
-
+		do_complete = true;
 		break;
 	case I2C_BUS_ERR_IND:
 		/* Bus error */
 		bus->cmd_err = -EAGAIN;
-		if (bus->master_or_slave == I2C_MASTER)
-			complete(&bus->cmd_complete);
-
+		do_complete = true;
 		break;
 	case I2C_WAKE_UP_IND:
 		/* I2C wake up */
@@ -752,6 +747,8 @@ static void npcm_i2c_callback(struct npcm_i2c *bus,
 	if (bus->slave)
 		bus->master_or_slave = I2C_SLAVE;
 #endif
+	if (do_complete)
+		complete(&bus->cmd_complete);
 }
 
 static u8 npcm_i2c_fifo_usage(struct npcm_i2c *bus)
-- 
2.42.0.515.g380fc7ccd1-goog