Patchwork [BUGFIX,2/4] PCI/PM: Keep parent bridge active when probing device

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Submitter Huang Ying
Date Aug. 3, 2012, 6:30 a.m.
Message ID <1343975435-25469-3-git-send-email-ying.huang@intel.com>
Download mbox | patch
Permalink /patch/174894/
State Superseded
Headers show

Comments

Huang Ying - Aug. 3, 2012, 6:30 a.m.
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>
---
 drivers/pci/pci-driver.c |    6 ++++++
 1 file changed, 6 insertions(+)

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Rafael J. Wysocki - Aug. 4, 2012, 9:48 p.m.
On Friday, August 03, 2012, Huang Ying wrote:
> 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>

Reviewed-by: Rafael J. Wysocki <rjw@sisk.pl>

> ---
>  drivers/pci/pci-driver.c |    6 ++++++
>  1 file changed, 6 insertions(+)
> 
> --- a/drivers/pci/pci-driver.c
> +++ b/drivers/pci/pci-driver.c
> @@ -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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Patch

--- a/drivers/pci/pci-driver.c
+++ b/drivers/pci/pci-driver.c
@@ -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;
 }