Commit ea8c88f1 authored Aug 08, 2012 by Huang Ying Committed by Bjorn Helgaas Aug 21, 2012

PCI/PM: Keep parent bridge active when probing device

This patch fixes the following bug:

http://marc.info/?l=linux-pci&m=134329923124234&w=2



The root cause of the bug is as follow.

If a device is not bound with the corresponding driver, the device
runtime PM will be disabled and the device will be put into suspended
state.  So that, the bridge/PCIe port connected to it may be put into
suspended and low power state.  When do probing for the device later,
because the bridge/PCIe port connected to it is in low power state,
the IO access to device may fail.

To solve the issue, the bridge/PCIe port connected to the device is
put into active state before probing.

Reported-by: Bjorn Mork <bjorn@mork.no>
Signed-off-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Rafael J. Wysocki <rjw@sisk.pl>

parent 4f9c1397

drivers/pci/pci-driver.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -280,8 +280,12 @@ static long local_pci_probe(void *_ddi)
		{
		struct drv_dev_and_id *ddi = _ddi;
		struct device *dev = &ddi->dev->dev;
		struct device *parent = dev->parent;
		int rc;

		/* The parent bridge must be in active state when probing */
		if (parent)
		pm_runtime_get_sync(parent);
		/* Unbound PCI devices are always set to disabled and suspended.
		* During probe, the device is set to enabled and active and the
		* usage count is incremented. If the driver supports runtime PM,
		@@ -298,6 +302,8 @@ static long local_pci_probe(void *_ddi)
		pm_runtime_set_suspended(dev);
		pm_runtime_put_noidle(dev);
		}
		if (parent)
		pm_runtime_put(parent);
		return rc;
		}

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