linux-kernel - [PATCH v3] i2c: aspeed: Fix i2c bus hang in slave read

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Message-Id: <20231006022233.3963590-1-zhangjian.3032@bytedance.com>
Date:   Fri,  6 Oct 2023 10:22:33 +0800
From:   Jian Zhang <zhangjian.3032@...edance.com>
To:     brendan.higgins@...ux.dev, benh@...nel.crashing.org,
        joel@....id.au, andrew@...id.au
Cc:     zhangjian3032@...il.com, yulei.sh@...edance.com,
        xiexinnan@...edance.com, Andi Shyti <andi.shyti@...nel.org>,
        Andrew Jeffery <andrew@...econstruct.com.au>,
        Tommy Huang <tommy_huang@...eedtech.com>,
        Wolfram Sang <wsa@...nel.org>,
        linux-i2c@...r.kernel.org (open list:ARM/ASPEED I2C DRIVER),
        openbmc@...ts.ozlabs.org (moderated list:ARM/ASPEED I2C DRIVER),
        linux-arm-kernel@...ts.infradead.org (moderated list:ARM/ASPEED MACHINE
        SUPPORT),
        linux-aspeed@...ts.ozlabs.org (moderated list:ARM/ASPEED MACHINE
        SUPPORT), linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v3] i2c: aspeed: Fix i2c bus hang in slave read

When the `CONFIG_I2C_SLAVE` option is enabled and the device operates
as a slave, a situation arises where the master sends a START signal
without the accompanying STOP signal. This action results in a
persistent I2C bus timeout. The core issue stems from the fact that
the i2c controller remains in a slave read state without a timeout
mechanism. As a consequence, the bus perpetually experiences timeouts.

In this case, the i2c bus will be reset, but the slave_state reset is
missing.

Fixes: fee465150b45 ("i2c: aspeed: Reset the i2c controller when timeout occurs")
Signed-off-by: Jian Zhang <zhangjian.3032@...edance.com>
Acked-by: Andi Shyti <andi.shyti@...nel.org>
Tested-by: Andrew Jeffery <andrew@...econstruct.com.au>
Reviewed-by: Andrew Jeffery <andrew@...econstruct.com.au>

---
Changelog:
 v3 - move to __aspeed_i2c_reg_slave.
 v2 - remove the i2c slave reset and only move the
 `bus->slave_state = ASPEED_I2C_SLAVE_INACTIVE` to the aspeed_i2c_init.
---
 drivers/i2c/busses/i2c-aspeed.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-aspeed.c b/drivers/i2c/busses/i2c-aspeed.c
index 5a416b39b818..28e2a5fc4528 100644
--- a/drivers/i2c/busses/i2c-aspeed.c
+++ b/drivers/i2c/busses/i2c-aspeed.c
@@ -749,6 +749,8 @@ static void __aspeed_i2c_reg_slave(struct aspeed_i2c_bus *bus, u16 slave_addr)
 	func_ctrl_reg_val = readl(bus->base + ASPEED_I2C_FUN_CTRL_REG);
 	func_ctrl_reg_val |= ASPEED_I2CD_SLAVE_EN;
 	writel(func_ctrl_reg_val, bus->base + ASPEED_I2C_FUN_CTRL_REG);
+
+	bus->slave_state = ASPEED_I2C_SLAVE_INACTIVE;
 }
 
 static int aspeed_i2c_reg_slave(struct i2c_client *client)
@@ -765,7 +767,6 @@ static int aspeed_i2c_reg_slave(struct i2c_client *client)
 	__aspeed_i2c_reg_slave(bus, client->addr);
 
 	bus->slave = client;
-	bus->slave_state = ASPEED_I2C_SLAVE_INACTIVE;
 	spin_unlock_irqrestore(&bus->lock, flags);
 
 	return 0;
-- 
2.30.2