On Mon, Apr 25, 2016 at 11:53 AM, Mika Westerberg
<mika.westerberg@xxxxxxxxxxxxxxx> wrote:
> Add back runtime PM support for PCIe ports that was removed in
> commit fe9a743a2601 ("PCI/PM: Drop unused runtime PM support code for
> PCIe ports").
>
> First of all we cannot enable it automatically for all ports since there
> has been problems previously as can be seen in [1]. In summary suspended
> PCIe ports were not able to deal with ACPI based hotplug reliably. One
> reason why this might happen is the fact that when a PCIe port is powered
> down, config space access to the devices behind the port is not possible.
> If the BIOS hotplug SMI handler assumes the port is always in D0 it will
> not be able to find the hotplugged devices. To be on the safe side only
> enable runtime PM if the port does not claim to support hotplug.
>
> For PCIe ports not using hotplug we enable and allow runtime PM
> automatically. Since 'bridge_d3' can be changed any time we check this in
> driver ->runtime_idle() and ->runtime_suspend() and only allow runtime
> suspend if the flag is still set. Use autosuspend with default of 10ms idle
> time to prevent the port from repeatedly suspending and resuming on
> continuous configuration space access of devices behind the port.
>
> The actual power transition to D3 and back is handled in the PCI core.
>
> Idea to automatically unblock (allow) runtime PM for PCIe ports came from
> Dave Airlie.
>
> [1] https://bugzilla.kernel.org/show_bug.cgi?id=53811
>
> Signed-off-by: Lukas Wunner <lukas@xxxxxxxxx>
> Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> ---
> drivers/pci/pcie/portdrv_core.c | 2 ++
> drivers/pci/pcie/portdrv_pci.c | 51 +++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 53 insertions(+)
>
> diff --git a/drivers/pci/pcie/portdrv_core.c b/drivers/pci/pcie/portdrv_core.c
> index 88122dc2e1b1..65b1a624826b 100644
> --- a/drivers/pci/pcie/portdrv_core.c
> +++ b/drivers/pci/pcie/portdrv_core.c
> @@ -11,6 +11,7 @@
> #include <linux/kernel.h>
> #include <linux/errno.h>
> #include <linux/pm.h>
> +#include <linux/pm_runtime.h>
> #include <linux/string.h>
> #include <linux/slab.h>
> #include <linux/pcieport_if.h>
> @@ -343,6 +344,7 @@ static int pcie_device_init(struct pci_dev *pdev, int service, int irq)
> get_descriptor_id(pci_pcie_type(pdev), service));
> device->parent = &pdev->dev;
> device_enable_async_suspend(device);
> + pm_runtime_no_callbacks(device);
>
> retval = device_register(device);
> if (retval) {
> diff --git a/drivers/pci/pcie/portdrv_pci.c b/drivers/pci/pcie/portdrv_pci.c
> index 6c6bb03392ea..22ee69dc8773 100644
> --- a/drivers/pci/pcie/portdrv_pci.c
> +++ b/drivers/pci/pcie/portdrv_pci.c
> @@ -93,6 +93,27 @@ static int pcie_port_resume_noirq(struct device *dev)
> return 0;
> }
>
> +static int pcie_port_runtime_suspend(struct device *dev)
> +{
> + return to_pci_dev(dev)->bridge_d3 ? 0 : -EBUSY;
> +}
> +
> +static int pcie_port_runtime_resume(struct device *dev)
> +{
> + pm_runtime_mark_last_busy(dev);
> + return 0;
> +}
> +
> +static int pcie_port_runtime_idle(struct device *dev)
> +{
> + /*
> + * Rely the PCI core has set bridge_d3 whenever it thinks the port
> + * should be good to go to D3. Everything else, including moving
> + * the port to D3, is handled by the PCI core.
> + */
> + return to_pci_dev(dev)->bridge_d3 ? 0 : -EBUSY;
> +}
> +
> static const struct dev_pm_ops pcie_portdrv_pm_ops = {
> .suspend = pcie_port_device_suspend,
> .resume = pcie_port_device_resume,
> @@ -101,6 +122,9 @@ static const struct dev_pm_ops pcie_portdrv_pm_ops = {
> .poweroff = pcie_port_device_suspend,
> .restore = pcie_port_device_resume,
> .resume_noirq = pcie_port_resume_noirq,
> + .runtime_suspend = pcie_port_runtime_suspend,
> + .runtime_resume = pcie_port_runtime_resume,
> + .runtime_idle = pcie_port_runtime_idle,
> };
>
> #define PCIE_PORTDRV_PM_OPS (&pcie_portdrv_pm_ops)
> @@ -134,11 +158,38 @@ static int pcie_portdrv_probe(struct pci_dev *dev,
> return status;
>
> pci_save_state(dev);
> +
> + /*
> + * Prevent runtime PM if the port is advertising support for PCIe
> + * hotplug. Otherwise the BIOS hotplug SMI code might not be able
> + * to enumerate devices behind this port properly (the port is
> + * powered down preventing all config space accesses to the
> + * subordinate devices). We can't be sure for native PCIe hotplug
> + * either so prevent that as well.
> + */
> + if (!dev->is_hotplug_bridge) {
> + /*
> + * Keep the port resumed 10ms to make sure things like
> + * config space accesses from userspace (lspci) will not
> + * cause the port to repeatedly suspend and resume.
> + */
> + pm_runtime_set_autosuspend_delay(&dev->dev, 10);
> + pm_runtime_use_autosuspend(&dev->dev);
> + pm_runtime_put_autosuspend(&dev->dev);
> + pm_runtime_allow(&dev->dev);
> + }
> +
> return 0;
> }
>
> static void pcie_portdrv_remove(struct pci_dev *dev)
> {
> + if (!dev->is_hotplug_bridge) {
> + pm_runtime_forbid(&dev->dev);
> + pm_runtime_get_noresume(&dev->dev);
> + pm_runtime_dont_use_autosuspend(&dev->dev);
> + }
> +
> pcie_port_device_remove(dev);
> }
>
> --
> 2.8.0.rc3
>
> --
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