[PATCH] i2c: i801: Ensure that SMBHSTSTS_INUSE_STS is cleared when leaving i801_access

[PATCH] i2c: i801: Ensure that SMBHSTSTS_INUSE_STS is cleared when leaving i801_access

[Heiner Kallweit]

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>
---
 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 c7d96cf5e..ab3470e77 100644
--- a/drivers/i2c/busses/i2c-i801.c
+++ b/drivers/i2c/busses/i2c-i801.c
@@ -948,6 +948,9 @@ 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);
-- 
2.31.1

Re: [PATCH] i2c: i801: Ensure that SMBHSTSTS_INUSE_STS is cleared when leaving i801_access

[Greg KH]

On Sun, Jun 06, 2021 at 03:41:03PM +0200, Heiner Kallweit wrote:
> 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>
> ---
>  drivers/i2c/busses/i2c-i801.c | 3 +++
>  1 file changed, 3 insertions(+)
> 


<formletter>

This is not the correct way to submit patches for inclusion in the
stable kernel tree.  Please read:
    https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.

</formletter>