On Tue, Aug 25, 2009 at 06:13:32AM +0800, Rafael J. Wysocki wrote:
> On Monday 24 August 2009, Shaohua Li wrote:
> >
> > PCIe defines a native PME detection mechanism. When a PCIe endpoint
> > invokes PME, PCIe root port has a set of regisets to detect the
> > endpoint's bus/device/function number and root port will send out
> > interrupt when PME is received. After getting interrupt, OS can identify
> > which device invokes PME according to such information. See PCIe
> > spec for detail. This patch implements this feature.
> >
> > Signed-off-by: Shaohua Li <shaohua.li@xxxxxxxxx>
> > ---
> > drivers/pci/pcie/Kconfig | 8 +
> > drivers/pci/pcie/Makefile | 2
> > drivers/pci/pcie/pcie_npme.c | 327 +++++++++++++++++++++++++++++++++++++++++++
> > 3 files changed, 337 insertions(+)
> >
> > Index: linux/drivers/pci/pcie/Kconfig
> > ===================================================================
> > --- linux.orig/drivers/pci/pcie/Kconfig 2009-08-24 15:38:46.000000000 +0800
> > +++ linux/drivers/pci/pcie/Kconfig 2009-08-24 15:47:09.000000000 +0800
> > @@ -46,3 +46,11 @@ config PCIEASPM_DEBUG
> > help
> > This enables PCI Express ASPM debug support. It will add per-device
> > interface to control ASPM.
> > +
> > +config PCIE_NPME
> > + bool "PCIe Native PME reporint(Experimental)"
> > + depends on PCIEPORTBUS && PM_RUNTIME && EXPERIMENTAL
> > + help
> > + This enables PCI Express Native PME Reporting. When device invokes
> > + PME, root port or root complex event collector can report the PME
> > + events to OS.
>
> Well, I think we can just drop the CONFIG option and make the whole thing
> depend on PM_RUNTIME && PCIEPORTBUS. So make it
This isn't always required, the ACPI approach still works. But fine, I'll do it.
> +config PCIE_PME
> + def_bool y
> + depends on PCIEPORTBUS && PM_RUNTIME && EXPERIMENTAL
>
> Ah, please drop the 'N' as I've just done. It doesn't carry any substantial
> information and is confusing IMO. Please also drop it from the function names
> below.
I don't want to drop the 'N'. The spec calls it native pme, so it's natural to
name the driver npme.
> > +#define PCI_EXP_RTSTA_PME 0x10000 /* PME status */
> > +
> > +static int disabled;
> > +module_param(disabled, bool, 0);
> > +static int force = 1;
> > +module_param(force, bool, 0);
>
> Why would anyone want to force it or disable it at this level?
In ACPI platform, we need call _OSC to declare the feature before we can use it.
Some BIOSes simply don't provide _OSC or implement it wrong. Per spec, we can't
enable the feature in such cases, so I provide an option to force it enabled.
The 'disabled' option is in case the feature doesn't work.
> > +
> > +struct pcie_npme_service_data {
> > + spinlock_t lock;
> > + struct pcie_device *dev;
> > + struct work_struct work;
> > + int in_exiting; /* driver is exiting, don't reenable interrupt */
> > +};
> > +
>
> Please add kerneldoc comments to all new functions
>
> > +static inline void pcie_npme_enable_interrupt(struct pci_dev *pdev, bool enable)
> > +{
> > + int pos;
> > + u16 rtctl;
> > +
> > + pos = pci_find_capability(pdev, PCI_CAP_ID_EXP);
> > +
> > + pci_read_config_word(pdev, pos + PCI_EXP_RTCTL, &rtctl);
> > + if (enable)
> > + rtctl |= PCI_EXP_RTCTL_PMEIE;
> > + else
> > + rtctl &= ~PCI_EXP_RTCTL_PMEIE;
> > + pci_write_config_word(pdev, pos + PCI_EXP_RTCTL, rtctl);
> > +}
> > +
> > +static inline void pcie_npme_clear_status(struct pci_dev *pdev)
> > +{
> > + int pos;
> > + u32 rtsta;
> > +
> > + pos = pci_find_capability(pdev, PCI_CAP_ID_EXP);
> > +
> > + pci_read_config_dword(pdev, pos + PCI_EXP_RTSTA, &rtsta);
> > + rtsta |= PCI_EXP_RTSTA_PME;
> > + pci_write_config_dword(pdev, pos + PCI_EXP_RTSTA, rtsta);
> > +}
> > +
> > +static bool pcie_npme_handle_request(struct pci_dev *root_port, u16 request_id)
>
> requester_id would be better.
ok
> > +{
> > + struct pci_dev *target;
> > + bool device_found = false;
> > + u8 busnr = request_id >> 8, devfn = request_id & 0xff;
> > +
> > + target = pci_get_bus_and_slot(busnr, devfn);
> > + /*
> > + * PME from PCI devices under a PCIe-to-PCI bridge may be converted to
> > + * a PCIe in-band PME message. In such case, bridge will assign the
> > + * message a new request id using bridge's secondary bus numer and
> > + * device number/function number 0
> > + */
> > + if (!target && devfn == 0) {
>
> + if (!target && !devfn) {
>
> Or better
>
> + if (target) {
> + ret = pci_pm_wakeup(target);
> + pci_dev_put(target);
> + return ret;
> + }
>
> BTW, what we do if target is NULL, but devfn is nonzero?
>From my understanding of PCIe bridge spec, the bridge always makes the devfn to zero
for legacy pci request upstream.
> > + struct pci_bus *bus;
> > +
> > + bus = pci_find_bus(pci_domain_nr(root_port->bus), busnr);
> > + if (bus) {
> > + target = bus->self;
> > + if (!target->is_pcie || target->pcie_type !=
> > + PCI_EXP_TYPE_PCI_BRIDGE)
>
> + if (!target->is_pcie
> + || target->pcie_type != PCI_EXP_TYPE_PCI_BRIDGE)
>
> > + target = NULL;
> > + }
> > + if (target)
> > + pci_dev_get(target);
>
> Now we don't need to do the _get().
ok
> > + }
> > +
> > + if (target)
> > + device_found = pci_pm_handle_wakeup_event(target);
>
> Now we call the function that searches over the hierarchy below the bridge.
>
> > + else
> > + printk(KERN_ERR"Can't find device %02d:%d.%d which invokes PME\n",
> > + busnr, PCI_SLOT(devfn), PCI_FUNC(devfn));
> > +
> > + if (target)
> > + pci_dev_put(target);
>
> The two lines above aren't necessary any more.
> > +
> > + return device_found;
> > +}
> > +
> > +static void pcie_npme_work_handle(struct work_struct *work)
> > +{
> > + struct pcie_npme_service_data *data =
> > + container_of(work, struct pcie_npme_service_data, work);
> > + struct pci_dev *root_port = data->dev->port;
> > + unsigned long flags;
> > + bool spurious = true;
> > + u32 rtsta;
> > + int pos;
> > +
> > + pos = pci_find_capability(root_port, PCI_CAP_ID_EXP);
> > + while (1) {
> > + spin_lock_irqsave(&data->lock, flags);
> > + pci_read_config_dword(root_port, pos + PCI_EXP_RTSTA, &rtsta);
> > +
> > + if (!(rtsta & PCI_EXP_RTSTA_PME)) {
> > + spin_unlock_irqrestore(&data->lock, flags);
> > + break;
> > + }
> > +
> > + /* clear PME, if there are other pending PME, the status will
> > + * get set again
> > + */
> > + pcie_npme_clear_status(root_port);
> > + spin_unlock_irqrestore(&data->lock, flags);
> > +
> > + if (pcie_npme_handle_request(root_port, rtsta & 0xffff))
> > + spurious = false;
> > + }
>
> It doesn't work like this if my reading of the spec is correct. Namely,
> we should get a separate interrupt for each device that generated a PME,
> so it's only necessary to clear the status without looping.
>
> Moreover, I think we should do something like this:
>
> * interrrupt arrives
> * disable interrupt
> * read the requester ID, schedule the service
> * clear the status
> * enable interrupt
>
> which now will allow us to get the interrupt for another device, if any.
> The spec seems to require devices not to generate PME messages continously,
> but only if they are not handled within a "reasonable amount of time" (original
> wording), so we should be safe from interrupt flooding.
>
> Note that we need to create a separate work_struct for each interrupt in this
> case, though.
I have different understanding. The root port can buffer several PME requests from
different devices. If the PME pending bit is set and after the status is clear,
the status bit will get set soon. We can do one request one time for each interrupt,
but seems not necessary. And the loop makes OS more quickly handle PME request without
overflow root port buffer.
> > +
> > + if (!spurious && !data->in_exiting) {
> > + spin_lock_irqsave(&data->lock, flags);
> > + /* reenable native PME */
> > + pcie_npme_enable_interrupt(root_port, true);
> > + spin_unlock_irqrestore(&data->lock, flags);
> > + }
> > +
> > + if (spurious)
> > + printk(KERN_ERR"Spurious Native PME interrupt %d received\n",
> > + root_port->irq);
> > +}
> > +
> > +static irqreturn_t pcie_npme_irq(int irq, void *context)
> > +{
> > + int pos;
> > + struct pci_dev *pdev;
> > + u32 rtsta;
> > + struct pcie_npme_service_data *data;
> > + unsigned long flags;
> > +
> > + pdev = ((struct pcie_device *)context)->port;
> > + data = get_service_data((struct pcie_device *)context);
> > +
> > + pos = pci_find_capability(pdev, PCI_CAP_ID_EXP);
> > +
> > + spin_lock_irqsave(&data->lock, flags);
> > + pci_read_config_dword(pdev, pos + PCI_EXP_RTSTA, &rtsta);
> > +
> > + if (!(rtsta & PCI_EXP_RTSTA_PME)) {
> > + spin_unlock_irqrestore(&data->lock, flags);
> > + return IRQ_NONE;
> > + }
> > +
> > + /* disable PME to avoid interrupt flood */
> > + pcie_npme_enable_interrupt(pdev, false);
> > + spin_unlock_irqrestore(&data->lock, flags);
> > +
> > + queue_work(pm_wq, &data->work);
>
> IMO, we should read the requester ID here and put it into the work struct as
> per the comment above.
see my above comment.
> Also, since in principle the interrupt may be shared with Hot-Plug Events,
> we should be careful about returning IRQ_HANDLED. Perhaps we should at least
> check if the requester ID is nonzero?
This is overthinking. Unless the hardware is broken, we don't need this.
> > +
> > + return IRQ_HANDLED;
> > +}
> > +
> > +#ifdef CONFIG_ACPI
> > +static int pcie_npme_osc_setup(struct pcie_device *pciedev)
> > +{
> > + acpi_status status = AE_NOT_FOUND;
> > + struct pci_dev *pdev = pciedev->port;
> > + acpi_handle handle = DEVICE_ACPI_HANDLE(&pdev->dev);
> > +
> > + if (!handle)
> > + return -EINVAL;
> > + status = acpi_pci_osc_control_set(handle,
> > + OSC_PCI_EXPRESS_PME_CONTROL |
> > + OSC_PCI_EXPRESS_CAP_STRUCTURE_CONTROL);
> > +
> > + if (ACPI_FAILURE(status)) {
> > + printk(KERN_DEBUG "Native PME service couldn't init device "
> > + "%s - %s\n", dev_name(&pciedev->device),
> > + (status == AE_SUPPORT || status == AE_NOT_FOUND) ?
> > + "no _OSC support" : "Run ACPI _OSC fails");
> > + return -EINVAL;
> > + }
> > +
> > + return 0;
> > +}
> > +#else
> > +static inline int pcie_npme_osc_setup(struct pcie_device *pciedev)
> > +{
> > + return 0;
> > +}
> > +#endif
> > +
> > +static int __devinit pcie_npme_probe(struct pcie_device *dev)
> > +{
> > + struct pci_dev *pdev;
> > + int status;
> > + struct pcie_npme_service_data *data;
> > +
> > + if (pcie_npme_osc_setup(dev) && !force)
> > + return -EINVAL;
> > +
> > + data = kzalloc(sizeof(*data), GFP_KERNEL);
> > + if (!data)
> > + return -ENOMEM;
> > + spin_lock_init(&data->lock);
> > + INIT_WORK(&data->work, pcie_npme_work_handle);
> > + data->dev = dev;
> > + set_service_data(dev, data);
> > +
> > + pdev = dev->port;
> > +
> > + /* clear pending PME */
> > + pcie_npme_clear_status(pdev);
> > +
> > + status = request_irq(dev->irq, pcie_npme_irq, IRQF_SHARED,
> > + "pcie_npme", dev);
> > + if (status) {
> > + kfree(data);
> > + return status;
> > + }
> > +
> > + /* enable PME interrupt */
> > + pcie_npme_enable_interrupt(pdev, true);
> > +
> > + return 0;
> > +}
> > +
> > +static void pcie_npme_remove(struct pcie_device *dev)
> > +{
> > + struct pci_dev *pdev;
> > + unsigned long flags;
> > + struct pcie_npme_service_data *data = get_service_data(dev);
> > +
> > + pdev = dev->port;
> > +
> > + /* disable PME interrupt */
> > + spin_lock_irqsave(&data->lock, flags);
> > + data->in_exiting = 1;
> > + pcie_npme_enable_interrupt(pdev, false);
> > + spin_unlock_irqrestore(&data->lock, flags);
> > +
> > + flush_scheduled_work();
> > + free_irq(dev->irq, dev);
> > +
> > + /* clear pending PME */
> > + pcie_npme_clear_status(pdev);
> > +
> > + set_service_data(dev, NULL);
> > + kfree(data);
> > +}
> > +
> > +static int pcie_npme_suspend(struct pcie_device *dev)
> > +{
> > + struct pci_dev *pdev;
> > + struct pcie_npme_service_data *data;
> > + unsigned long flags;
> > +
> > + pdev = dev->port;
> > + data = get_service_data(dev);
> > +
> > + spin_lock_irqsave(&data->lock, flags);
> > + /* disable PME to avoid further interrupt */
> > + pcie_npme_enable_interrupt(pdev, false);
> > +
> > + /* clear pending PME */
> > + pcie_npme_clear_status(pdev);
> > + spin_unlock_irqrestore(&data->lock, flags);
> > +
> > + return 0;
> > +}
> > +
> > +static int pcie_npme_resume(struct pcie_device *dev)
> > +{
> > + struct pci_dev *pdev = dev->port;
> > + unsigned long flags;
> > + struct pcie_npme_service_data *data = get_service_data(dev);
> > +
> > + spin_lock_irqsave(&data->lock, flags);
> > + pcie_npme_clear_status(pdev);
> > + pcie_npme_enable_interrupt(pdev, true);
> > + spin_unlock_irqrestore(&data->lock, flags);
> > +
> > + return 0;
> > +}
> > +
> > +static struct pcie_port_service_driver pcie_npme_driver = {
> > + .name = "pcie_npme",
> > + .port_type = PCIE_RC_PORT,
> > + .service = PCIE_PORT_SERVICE_PME,
> > +
> > + .probe = pcie_npme_probe,
> > + .remove = pcie_npme_remove,
> > + .suspend = pcie_npme_suspend,
> > + .resume = pcie_npme_resume,
> > +};
> > +
> > +static int __init pcie_npme_service_init(void)
> > +{
> > + if (disabled)
> > + return -EINVAL;
> > + return pcie_port_service_register(&pcie_npme_driver);
> > +}
> > +
> > +static void __exit pcie_npme_service_exit(void)
> > +{
> > + pcie_port_service_unregister(&pcie_npme_driver);
> > +}
> > +
> > +module_init(pcie_npme_service_init);
> > +module_exit(pcie_npme_service_exit);
> > +
> > +MODULE_AUTHOR("Shaohua Li<shaohua.li@xxxxxxxxx>");
> > +MODULE_LICENSE("GPL");
>
> I'm not entirely sure if that should be a module. Perhaps it sholdn't.
Ok.
Thanks,
Shaohua
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