Re: [BUGFIX 3/4] PCI/PM: Fix config reg access for D3cold and bridgesuspending

From: Alan Stern
Date: Fri Aug 03 2012 - 10:46:15 EST


On Fri, 3 Aug 2012, Huang Ying wrote:

> This patch fixes the following bug:
>
> http://marc.info/?l=linux-pci&m=134338059022620&w=2
>
> Where lspci does not work properly if a device and the corresponding
> parent bridge (such as PCIe port) is suspended. This is because the
> device configuration space registers will be not accessible if the
> corresponding parent bridge is suspended or the device is put into
> D3cold state.
>
> To solve the issue, the bridge/PCIe port connected to the device is
> put into active state before read/write configuration space registers.
> If the device is in D3cold state, it will be put into active state
> too.
>
> To avoid resume/suspend PCIe port for each configuration register
> read/write, a small delay is added before the PCIe port to go
> suspended.


> +static void
> +pci_config_pm_runtime_put(struct pci_dev *pdev)
> +{
> + struct device *dev = &pdev->dev;
> + struct device *parent = dev->parent;
> +
> + pm_runtime_put(dev);
> + if (parent)
> + pm_runtime_put(parent);
> +}

This is just the sort of thing Rafael and I have been talking about.
Why do an asynchronous put, going to all the trouble of using the
workqueue, if the idle routine is just going to call
pm_schedule_suspend()?

Why not call pm_runtime_put_sync() instead?

Alan Stern

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