On Mon, May 23, 2016 at 11:20:48AM +0300, Mika Westerberg wrote:
> When a PCI device is removed through sysfs interface the upstream bridge
> (PCIe port) can be runtime suspended if it was the last device on that bus.
> Now, if the bridge is in D3 we cannot find devices below the bridge
> anymore. For example following fails to find the removed device again:
>
> # echo 1 > /sys/bus/pci/devices/0000:00:01.0/0000:01:00.0/remove
> # echo 1 > /sys/bus/pci/devices/0000:00:01.0/rescan
>
> Where 0000:00:01.0 is the bridge device.
>
> In order to be able to rescan devices below the bridge add
> pm_runtime_get_sync()/pm_runtime_put() calls to pci_scan_bridge(). This
> should keep bridges powered on while their children devices are being
> scanned.
>
> Reported-by: Peter Wu <peter@xxxxxxxxxxxxx>
> Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
This looks like basically the same idea as "ACPI / hotplug / PCI:
Runtime resume bridge before rescan".
The hotplug_event() path modified by that patch eventually calls
pci_scan_bridge():
hotplug_event
enable_slot
pci_scan_bridge
so this patch looks a little more general. Does it make "ACPI /
hotplug / PCI: Runtime resume bridge before rescan" unnecessary?
Can I just replace that patch with this one?
> ---
> drivers/pci/probe.c | 9 +++++++++
> 1 file changed, 9 insertions(+)
>
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 8004f67c57ec..15e77c92311e 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -16,6 +16,7 @@
> #include <linux/aer.h>
> #include <linux/acpi.h>
> #include <linux/irqdomain.h>
> +#include <linux/pm_runtime.h>
> #include "pci.h"
>
> #define CARDBUS_LATENCY_TIMER 176 /* secondary latency timer */
> @@ -832,6 +833,12 @@ int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max, int pass)
> u8 primary, secondary, subordinate;
> int broken = 0;
>
> + /*
> + * Make sure the bridge is powered on to be able to access config
> + * space of devices below it.
> + */
> + pm_runtime_get_sync(&dev->dev);
> +
> pci_read_config_dword(dev, PCI_PRIMARY_BUS, &buses);
> primary = buses & 0xFF;
> secondary = (buses >> 8) & 0xFF;
> @@ -1012,6 +1019,8 @@ int pci_scan_bridge(struct pci_bus *bus, struct pci_dev *dev, int max, int pass)
> out:
> pci_write_config_word(dev, PCI_BRIDGE_CONTROL, bctl);
>
> + pm_runtime_put(&dev->dev);
> +
> return max;
> }
> EXPORT_SYMBOL(pci_scan_bridge);
> --
> 2.8.1
>
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