[PATCH] i2c: i801: Restore INTREN on unload

[Jean Delvare <jdelvare@suse.de>]

If driver interrupts are enabled, SMBHSTCNT_INTREN will be 1 after
the first transaction, and will stay to that value forever. This
means that interrupts will be generated for both host-initiated
transactions and also SMBus Alert events even after the driver is
unloaded. To be on the safe side, we should restore the initial state
of this bit at suspend and reboot time, as we do for several other
configuration bits already and for the same reason: the BIOS should
be handed the device in the same configuration state in which we
received it. Otherwise interrupts may be generated which nobody
will process.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Tested-by: Jarkko Nikula <jarkko.nikula@linux.intel.com>
---
This probably doesn't change much on its own in practice, however it
is mandatory to make this change before Jarkko's fix for the SMB_ALERT
interrupt storm gets applied, otherwise the fix will be incomplete.

Jarkko, this is not exactly the patch you tested, I added restoration
to the suspend path as well to be 100% safe.

 drivers/i2c/busses/i2c-i801.c |    7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

--- linux-5.14.orig/drivers/i2c/busses/i2c-i801.c	2021-11-09 15:51:03.186452787 +0100
+++ linux-5.14/drivers/i2c/busses/i2c-i801.c	2021-11-09 15:56:05.081477077 +0100
@@ -258,6 +258,7 @@ struct i801_priv {
 	struct i2c_adapter adapter;
 	unsigned long smba;
 	unsigned char original_hstcfg;
+	unsigned char original_hstcnt;
 	unsigned char original_slvcmd;
 	struct pci_dev *pci_dev;
 	unsigned int features;
@@ -1799,7 +1800,8 @@ static int i801_probe(struct pci_dev *de
 		outb_p(inb_p(SMBAUXCTL(priv)) &
 		       ~(SMBAUXCTL_CRC | SMBAUXCTL_E32B), SMBAUXCTL(priv));
 
-	/* Remember original Host Notify setting */
+	/* Remember original Interrupt and Host Notify settings */
+	priv->original_hstcnt = inb_p(SMBHSTCNT(priv)) & ~SMBHSTCNT_KILL;
 	if (priv->features & FEATURE_HOST_NOTIFY)
 		priv->original_slvcmd = inb_p(SMBSLVCMD(priv));
 
@@ -1863,6 +1865,7 @@ static void i801_remove(struct pci_dev *
 {
 	struct i801_priv *priv = pci_get_drvdata(dev);
 
+	outb_p(priv->original_hstcnt, SMBHSTCNT(priv));
 	i801_disable_host_notify(priv);
 	i801_del_mux(priv);
 	i2c_del_adapter(&priv->adapter);
@@ -1886,6 +1889,7 @@ static void i801_shutdown(struct pci_dev
 	struct i801_priv *priv = pci_get_drvdata(dev);
 
 	/* Restore config registers to avoid hard hang on some systems */
+	outb_p(priv->original_hstcnt, SMBHSTCNT(priv));
 	i801_disable_host_notify(priv);
 	pci_write_config_byte(dev, SMBHSTCFG, priv->original_hstcfg);
 }
@@ -1895,6 +1899,7 @@ static int i801_suspend(struct device *d
 {
 	struct i801_priv *priv = dev_get_drvdata(dev);
 
+	outb_p(priv->original_hstcnt, SMBHSTCNT(priv));
 	pci_write_config_byte(priv->pci_dev, SMBHSTCFG, priv->original_hstcfg);
 	return 0;
 }

-- 
Jean Delvare
SUSE L3 Support