Re: [PATCH 5/5] pci: Add support for polling PME state on suspended legacy PCI devices

["Rafael J. Wysocki" <rjw@sisk.pl>]

On Monday, October 04, 2010, Matthew Garrett wrote:
> Not all hardware vendors hook up the PME line for legacy PCI devices,
> meaning that wakeup events get lost. The only way around this is to poll
> the devices to see if their state has changed, so add support for doing
> that on legacy PCI devices that aren't part of the core chipset.
> 
> Signed-off-by: Matthew Garrett <mjg@redhat.com>

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

> ---
>  drivers/pci/pci.c |   77 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 files changed, 77 insertions(+), 0 deletions(-)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index 7fa3cbd..0b61263 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -38,6 +38,19 @@ EXPORT_SYMBOL(pci_pci_problems);
>  
>  unsigned int pci_pm_d3_delay;
>  
> +static void pci_pme_list_scan(struct work_struct *work);
> +
> +static LIST_HEAD(pci_pme_list);
> +static DEFINE_MUTEX(pci_pme_list_mutex);
> +static DECLARE_DELAYED_WORK(pci_pme_work, pci_pme_list_scan);
> +
> +struct pci_pme_device {
> +	struct list_head list;
> +	struct pci_dev *dev;
> +};
> +
> +#define PME_TIMEOUT 1000 /* How long between PME checks */
> +
>  static void pci_dev_d3_sleep(struct pci_dev *dev)
>  {
>  	unsigned int delay = dev->d3_delay;
> @@ -1331,6 +1344,32 @@ bool pci_pme_capable(struct pci_dev *dev, pci_power_t state)
>  	return !!(dev->pme_support & (1 << state));
>  }
>  
> +static void pci_pme_list_scan(struct work_struct *work)
> +{
> +	struct pci_pme_device *pme_dev;
> +
> +	mutex_lock(&pci_pme_list_mutex);
> +	if (!list_empty(&pci_pme_list)) {
> +		list_for_each_entry(pme_dev, &pci_pme_list, list)
> +			pci_pme_wakeup(pme_dev->dev, NULL);
> +		schedule_delayed_work(&pci_pme_work, msecs_to_jiffies(PME_TIMEOUT));
> +	}
> +	mutex_unlock(&pci_pme_list_mutex);
> +}
> +
> +/**
> + * pci_external_pme - is a device an external PCI PME source?
> + * @dev: PCI device to check
> + *
> + */
> +
> +static bool pci_external_pme(struct pci_dev *dev)
> +{
> +	if (pci_is_pcie(dev) || dev->bus->number == 0)
> +		return false;
> +	return true;
> +}
> +
>  /**
>   * pci_pme_active - enable or disable PCI device's PME# function
>   * @dev: PCI device to handle.
> @@ -1354,6 +1393,44 @@ void pci_pme_active(struct pci_dev *dev, bool enable)
>  
>  	pci_write_config_word(dev, dev->pm_cap + PCI_PM_CTRL, pmcsr);
>  
> +	/* PCI (as opposed to PCIe) PME requires that the device have
> +	   its PME# line hooked up correctly. Not all hardware vendors
> +	   do this, so the PME never gets delivered and the device
> +	   remains asleep. The easiest way around this is to
> +	   periodically walk the list of suspended devices and check
> +	   whether any have their PME flag set. The assumption is that
> +	   we'll wake up often enough anyway that this won't be a huge
> +	   hit, and the power savings from the devices will still be a
> +	   win. */
> +
> +	if (pci_external_pme(dev)) {
> +		struct pci_pme_device *pme_dev;
> +		if (enable) {
> +			pme_dev = kmalloc(sizeof(struct pci_pme_device),
> +					  GFP_KERNEL);
> +			if (!pme_dev)
> +				goto out;
> +			pme_dev->dev = dev;
> +			mutex_lock(&pci_pme_list_mutex);
> +			list_add(&pme_dev->list, &pci_pme_list);
> +			if (list_is_singular(&pci_pme_list))
> +				schedule_delayed_work(&pci_pme_work,
> +						      msecs_to_jiffies(PME_TIMEOUT));
> +			mutex_unlock(&pci_pme_list_mutex);
> +		} else {
> +			mutex_lock(&pci_pme_list_mutex);
> +			list_for_each_entry(pme_dev, &pci_pme_list, list) {
> +				if (pme_dev->dev == dev) {
> +					list_del(&pme_dev->list);
> +					kfree(pme_dev);
> +					break;
> +				}
> +			}
> +			mutex_unlock(&pci_pme_list_mutex);
> +		}
> +	}
> +
> +out:
>  	dev_printk(KERN_DEBUG, &dev->dev, "PME# %s\n",
>  			enable ? "enabled" : "disabled");
>  }
>