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Date: Tue, 20 Nov 2012 22:38:45 +0100
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Huang Ying <ying.huang@...el.com>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>, linux-kernel@...r.kernel.org,
linux-pci@...r.kernel.org, linux-pm@...r.kernel.org,
"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
Alan Stern <stern@...land.harvard.edu>
Subject: Re: [PATCH] PCI/PM: Keep runtime PM enabled for unbound PCI devices
On Tuesday, November 20, 2012 04:08:22 PM Huang Ying wrote:
> For unbound PCI devices, what we need is:
>
> - Always in D0 state, because some devices does not work again after
> being put into D3 by the PCI bus.
>
> - In SUSPENDED state if allowed, so that the parent devices can still
> be put into low power state.
>
> To satisfy these requirement, the runtime PM for the unbound PCI
> devices are disabled and set to SUSPENDED state. One issue of this
> solution is that the PCI devices will be put into SUSPENDED state even
> if the SUSPENDED state is forbidden via the sysfs interface
> (.../power/control) of the device. This is not an issue for most
> devices, because most PCI devices are not used at all if unbounded.
> But there are exceptions. For example, unbound VGA card can be used
> for display, but suspend its parents make it stop working.
>
> To fix the issue, we keep the runtime PM enabled when the PCI devices
> are unbound. But the runtime PM callbacks will do nothing if the PCI
> devices are unbound. This way, we can put the PCI devices into
> SUSPENDED state without put the PCI devices into D3 state.
>
> Signed-off-by: Huang Ying <ying.huang@...el.com>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Cc: Alan Stern <stern@...land.harvard.edu>
> CC: stable@...r.kernel.org # v3.6+
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> drivers/pci/pci-driver.c | 69 +++++++++++++++++++++++++++--------------------
> drivers/pci/pci.c | 2 +
> 2 files changed, 43 insertions(+), 28 deletions(-)
>
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -1900,6 +1900,8 @@ void pci_pm_init(struct pci_dev *dev)
> u16 pmc;
>
> pm_runtime_forbid(&dev->dev);
> + pm_runtime_set_active(&dev->dev);
> + pm_runtime_enable(&dev->dev);
> device_enable_async_suspend(&dev->dev);
> dev->wakeup_prepared = false;
>
> --- a/drivers/pci/pci-driver.c
> +++ b/drivers/pci/pci-driver.c
> @@ -256,31 +256,26 @@ struct drv_dev_and_id {
> 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;
> + struct pci_dev *pci_dev = ddi->dev;
> + struct pci_driver *pci_drv = ddi->drv;
> + struct device *dev = &pci_dev->dev;
> 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,
> - * it should call pm_runtime_put_noidle() in its probe routine and
> - * pm_runtime_get_noresume() in its remove routine.
> - */
> - pm_runtime_get_noresume(dev);
> - pm_runtime_set_active(dev);
> - pm_runtime_enable(dev);
> -
> - rc = ddi->drv->probe(ddi->dev, ddi->id);
> + /*
> + * Unbound PCI devices are always put in D0, regardless of
> + * runtime PM status. During probe, the device is set to
> + * active and the usage count is incremented. If the driver
> + * supports runtime PM, it should call pm_runtime_put_noidle()
> + * in its probe routine and pm_runtime_get_noresume() in its
> + * remove routine.
> + */
> + pm_runtime_get_sync(dev);
> + pci_dev->driver = pci_drv;
> + rc = pci_drv->probe(pci_dev, ddi->id);
> if (rc) {
> - pm_runtime_disable(dev);
> - pm_runtime_set_suspended(dev);
> - pm_runtime_put_noidle(dev);
> + pci_dev->driver = NULL;
> + pm_runtime_put_sync(dev);
> }
> - if (parent)
> - pm_runtime_put(parent);
> return rc;
> }
>
> @@ -330,10 +325,8 @@ __pci_device_probe(struct pci_driver *dr
> id = pci_match_device(drv, pci_dev);
> if (id)
> error = pci_call_probe(drv, pci_dev, id);
> - if (error >= 0) {
> - pci_dev->driver = drv;
> + if (error >= 0)
> error = 0;
> - }
> }
> return error;
> }
> @@ -369,9 +362,7 @@ static int pci_device_remove(struct devi
> }
>
> /* Undo the runtime PM settings in local_pci_probe() */
> - pm_runtime_disable(dev);
> - pm_runtime_set_suspended(dev);
> - pm_runtime_put_noidle(dev);
> + pm_runtime_put_sync(dev);
>
> /*
> * If the device is still on, set the power state as "unknown",
> @@ -994,6 +985,13 @@ static int pci_pm_runtime_suspend(struct
> pci_power_t prev = pci_dev->current_state;
> int error;
>
> + /*
> + * If pci_dev->driver is not set (unbound), the device should
> + * always remain in D0 regardless of the runtime PM status
> + */
> + if (!pci_dev->driver)
> + return 0;
> +
> if (!pm || !pm->runtime_suspend)
> return -ENOSYS;
>
> @@ -1029,6 +1027,13 @@ static int pci_pm_runtime_resume(struct
> struct pci_dev *pci_dev = to_pci_dev(dev);
> const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
>
> + /*
> + * If pci_dev->driver is not set (unbound), the device should
> + * always remain in D0 regardless of the runtime PM status
> + */
> + if (!pci_dev->driver)
> + return 0;
> +
> if (!pm || !pm->runtime_resume)
> return -ENOSYS;
>
> @@ -1046,8 +1051,16 @@ static int pci_pm_runtime_resume(struct
>
> static int pci_pm_runtime_idle(struct device *dev)
> {
> + struct pci_dev *pci_dev = to_pci_dev(dev);
> const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
>
> + /*
> + * If pci_dev->driver is not set (unbound), the device should
> + * always remain in D0 regardless of the runtime PM status
> + */
> + if (!pci_dev->driver)
> + goto out;
> +
> if (!pm)
> return -ENOSYS;
>
> @@ -1057,8 +1070,8 @@ static int pci_pm_runtime_idle(struct de
> return ret;
> }
>
> +out:
> pm_runtime_suspend(dev);
> -
> return 0;
> }
>
> --
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>
--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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