Re: [PATCH] i2c: i801: Use PCI bus rescan mutex to protect P2SB access

[Andy Shevchenko <andriy.shevchenko@intel.com>]

On Sun, Sep 05, 2021 at 05:59:42PM +0200, Heiner Kallweit wrote:
> 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.

Thanks!
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>

> [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>
> ---
>  drivers/i2c/busses/i2c-i801.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
> index 89ae78ef1..1f929e6c3 100644
> --- 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)
> -- 
> 2.33.0
> 

-- 
With Best Regards,
Andy Shevchenko