Re: [PATCH] PCI: Make sure the bus bridge powered on when scanning bus

[Yicong Yang <yangyicong@hisilicon.com>]

gentle ping ...

Any comments on this or is it possible to be merged?


On 2020/7/29 19:30, Yicong Yang wrote:
> When the bus bridge is runtime suspended, we'll fail to rescan
> the devices through sysfs as we cannot access the configuration
> space correctly when the bridge is in D3hot.
> It can be reproduced like:
>
> $ echo 1 > /sys/bus/pci/devices/0000:80:00.0/0000:81:00.1/remove
> $ echo 1 > /sys/bus/pci/devices/0000:80:00.0/pci_bus/0000:81/rescan
>
> 0000:80:00.0 is root port and is runtime suspended and we cannot
> get 0000:81:00.1 after rescan.
>
> Make bridge powered on when scanning the child bus, by adding
> pm_runtime_get_sync()/pm_runtime_put() in pci_scan_child_bus_extend().
>
> Signed-off-by: Yicong Yang <yangyicong@hisilicon.com>
> ---
>  drivers/pci/probe.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 2f66988..5bb502b 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -2795,6 +2795,14 @@ static unsigned int pci_scan_child_bus_extend(struct pci_bus *bus,
>  
>  	dev_dbg(&bus->dev, "scanning bus\n");
>  
> +	/*
> +	 * Make sure the bus bridge is powered on, otherwise we may not be
> +	 * able to scan the devices as we may fail to access the configuration
> +	 * space of subordinates.
> +	 */
> +	if (bus->self)
> +		pm_runtime_get_sync(&bus->self->dev);
> +
>  	/* Go find them, Rover! */
>  	for (devfn = 0; devfn < 256; devfn += 8) {
>  		nr_devs = pci_scan_slot(bus, devfn);
> @@ -2907,6 +2915,9 @@ static unsigned int pci_scan_child_bus_extend(struct pci_bus *bus,
>  		}
>  	}
>  
> +	if (bus->self)
> +		pm_runtime_put(&bus->self->dev);
> +
>  	/*
>  	 * We've scanned the bus and so we know all about what's on
>  	 * the other side of any bridges that may be on this bus plus