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From:   Sasha Levin <sashal@kernel.org>
To:     linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc:     Heiner Kallweit <hkallweit1@gmail.com>,
        Hector Martin <marcan@marcan.st>,
        Jean Delvare <jdelvare@suse.de>, Wolfram Sang <wsa@kernel.org>,
        Sasha Levin <sashal@kernel.org>
Subject: [PATCH 5.12 064/110] i2c: i801: Ensure that SMBHSTSTS_INUSE_STS is cleared when leaving i801_access
Date:   Mon, 28 Jun 2021 10:17:42 -0400
Message-Id: <20210628141828.31757-65-sashal@kernel.org>
In-Reply-To: <20210628141828.31757-1-sashal@kernel.org>
References: <20210628141828.31757-1-sashal@kernel.org>
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From: Heiner Kallweit <hkallweit1@gmail.com>

[ Upstream commit 065b6211a87746e196b56759a70c7851418dd741 ]

As explained in [0] currently we may leave SMBHSTSTS_INUSE_STS set,
thus potentially breaking ACPI/BIOS usage of the SMBUS device.

Seems patch [0] needs a little bit more of review effort, therefore
I'd suggest to apply a part of it as quick win. Just clearing
SMBHSTSTS_INUSE_STS when leaving i801_access() should fix the
referenced issue and leaves more time for discussing a more
sophisticated locking handling.

[0] https://www.spinics.net/lists/linux-i2c/msg51558.html

Fixes: 01590f361e94 ("i2c: i801: Instantiate SPD EEPROMs automatically")
Suggested-by: Hector Martin <marcan@marcan.st>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Hector Martin <marcan@marcan.st>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Tested-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Wolfram Sang <wsa@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/i2c/busses/i2c-i801.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
index f9e1c2ceaac0..04a1e38f2a6f 100644
--- a/drivers/i2c/busses/i2c-i801.c
+++ b/drivers/i2c/busses/i2c-i801.c
@@ -978,6 +978,9 @@ static s32 i801_access(struct i2c_adapter *adap, u16 addr,
 	}
 
 out:
+	/* Unlock the SMBus device for use by BIOS/ACPI */
+	outb_p(SMBHSTSTS_INUSE_STS, SMBHSTSTS(priv));
+
 	pm_runtime_mark_last_busy(&priv->pci_dev->dev);
 	pm_runtime_put_autosuspend(&priv->pci_dev->dev);
 	mutex_unlock(&priv->acpi_lock);
-- 
2.30.2