i2c: i801: Use PCI bus rescan mutex to protect P2SB access

BugLink: https://bugs.launchpad.net/bugs/1951822
[ Upstream commit 7d6b61c394a42b8385858bb9e306d48a0112823c ]

As pointed out by Andy in [0] using a local mutex here isn't strictly
wrong but not sufficient. We should hold the PCI rescan lock for P2SB
operations.

[0] https://www.spinics.net/lists/linux-i2c/msg52717.html

Fixes: 1a987c69ce2c ("i2c: i801: make p2sb_spinlock a mutex")
Reported-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Reviewed-by: Jean Delvare <jdelvare@suse.de>
Signed-off-by: Wolfram Sang <wsa@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Paolo Pisati <paolo.pisati@canonical.com>

diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
index 89ae78ef1a1ccc153f67891848cf3602d825606b..1f929e6c30bea006e247f6b227b4c69f86eff7e1 100644 (file)
--- a/drivers/i2c/busses/i2c-i801.c
+++ b/drivers/i2c/busses/i2c-i801.c
@@ -1493,7 +1493,6 @@ static struct platform_device *
 i801_add_tco_spt(struct i801_priv *priv, struct pci_dev *pci_dev,
                 struct resource *tco_res)
 {
-       static DEFINE_MUTEX(p2sb_mutex);
        struct resource *res;
        unsigned int devfn;
        u64 base64_addr;
@@ -1506,7 +1505,7 @@ i801_add_tco_spt(struct i801_priv *priv, struct pci_dev *pci_dev,
         * enumerated by the PCI subsystem, so we need to unhide/hide it
         * to lookup the P2SB BAR.
         */
-       mutex_lock(&p2sb_mutex);
+       pci_lock_rescan_remove();
 
        devfn = PCI_DEVFN(PCI_SLOT(pci_dev->devfn), 1);
 
@@ -1524,7 +1523,7 @@ i801_add_tco_spt(struct i801_priv *priv, struct pci_dev *pci_dev,
        /* Hide the P2SB device, if it was hidden before */
        if (hidden)
                pci_bus_write_config_byte(pci_dev->bus, devfn, 0xe1, hidden);
-       mutex_unlock(&p2sb_mutex);
+       pci_unlock_rescan_remove();
 
        res = &tco_res[1];
        if (pci_dev->device == PCI_DEVICE_ID_INTEL_DNV_SMBUS)