Re: [RFC 4/5] PCIe native PME detection

Rafael J. Wysocki
2008-10-19T20:30:02Z

On Thursday, 11 of September 2008, 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. See PCIe spec for detail. This patch implements this feature.

Any details of the implementation?

> ---
> drivers/pci/pcie/Kconfig | 7 +
> drivers/pci/pcie/Makefile | 2
> drivers/pci/pcie/npme.c | 312 ++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/pci_regs.h | 1
> 4 files changed, 322 insertions(+)
>
> Index: linux/drivers/pci/pcie/Kconfig
> ===================================================================
> --- linux.orig/drivers/pci/pcie/Kconfig 2008-09-11 11:27:44.000000000 +0800
> +++ linux/drivers/pci/pcie/Kconfig 2008-09-11 11:28:39.000000000 +0800
> @@ -46,3 +46,10 @@ config PCIEASPM_DEBUG
> help
> This enables PCI Express ASPM debug support. It will add per-device
> interface to control ASPM.
> +
> +config PCIENPME
> + bool "PCIE Native PME support(Experimental)"
> + depends on PCIEPORTBUS && EXPERIMENTAL
> + help
> + This enables PCI Express Native PME Reporting.
> +
> Index: linux/drivers/pci/pcie/Makefile
> ===================================================================
> --- linux.orig/drivers/pci/pcie/Makefile 2008-09-11 11:27:44.000000000 +0800
> +++ linux/drivers/pci/pcie/Makefile 2008-09-11 11:28:39.000000000 +0800
> @@ -11,3 +11,5 @@ obj-$(CONFIG_PCIEPORTBUS) += pcieportdrv
>
> # Build PCI Express AER if needed
> obj-$(CONFIG_PCIEAER) += aer/
> +
> +obj-$(CONFIG_PCIENPME) += npme.o
> Index: linux/drivers/pci/pcie/npme.c
> ===================================================================
> --- /dev/null 1970-01-01 00:00:00.000000000 +0000
> +++ linux/drivers/pci/pcie/npme.c 2008-09-11 11:30:26.000000000 +0800
> @@ -0,0 +1,312 @@
> +/*
> + * PCIE Native PME support
> + *
> + * Copyright (C) 2007 - 2008 Intel Corp
> + * Shaohua Li <shaohua.li@intel.com>
> + *
> + * This file is subject to the terms and conditions of the GNU General Public
> + * License. See the file "COPYING" in the main directory of this archive
> + * for more details.
> + */
> +
> +#include <linux/module.h>
> +#include <linux/pci.h>
> +#include <linux/kernel.h>
> +#include <linux/errno.h>
> +#include <linux/init.h>
> +#include <linux/interrupt.h>
> +#include <linux/device.h>
> +#include <linux/pcieport_if.h>
> +#include <linux/acpi.h>
> +#include <linux/pci-acpi.h>
> +
> +static int disabled;
> +module_param(disabled, bool, 0);
> +static int force = 1;
> +module_param(force, bool, 0);
> +
> +static struct pcie_port_service_id npme_id[] = {
> + {
> + .vendor = PCI_ANY_ID,
> + .device = PCI_ANY_ID,
> + .port_type = PCIE_RC_PORT,
> + .service_type = PCIE_PORT_SERVICE_PME,
> + },
> + { /* end: all zeroes */ }
> +};
> +
> +struct npme_data {
> + spinlock_t lock;
> + struct pcie_device *dev;
> + struct work_struct work;
> + u16 bdf; /* device which invokes PME */
> + int exit;
> +};
> +
> +static inline void npme_enable_pme(struct pci_dev *pdev, bool enable)

This works in analogy with pci_pme_active(), so it would seem reasonable to
call it npme_pme_active(), although pcie_npme_active() would be even better
IMO.

> +{
> + int pos;
> + u16 rtctl;
> +
> + pos = pci_find_capability(pdev, PCI_CAP_ID_EXP);
> +

The result of this call seems to be a good candidate for caching in
'struct pci_dev'.

> + 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 npme_clear_pme(struct pci_dev *pdev)

pcie_npme_clear_status() perhaps?

> +{
> + int pos;
> + u32 rtsta;
> +
> + pos = pci_find_capability(pdev, PCI_CAP_ID_EXP);

Check if we found it?

> +
> + 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 npme_pme_target(struct pci_dev *target)
> +{
> + bool ret = false;
> + if (target->dev.bus->pm && target->dev.bus->pm->base.wakeup_event)
> + ret = target->dev.bus->pm->base.wakeup_event(&target->dev);
> + return ret;
> +}

This apparently only calls the device bus type's wakeup_event() method, so
perhaps give it a better name (pcie_npme_bus_callback() maybe?).

> +
> +static void npme_work_handle(struct work_struct *work)
> +{
> + struct npme_data *data = container_of(work, struct npme_data, work);

Is 'data' guaranteed to be not NULL?

> + struct pcie_device *dev = data->dev;
> + unsigned long flags;
> + struct pci_dev *target;
> + bool has_dev = false;
> +
> + target = pci_get_bus_and_slot(data->bdf >> 8, data->bdf & 0xff);
> + /* PCIe-PCI bridge might change bdf to (secondary bus numer, 0, 0) */
> + if (!target && (data->bdf & 0xff) == 0) {
> + struct pci_bus *bus;
> +
> + bus = pci_find_bus(pci_domain_nr(dev->port->bus),
> + data->bdf >> 8);

Is 'dev' guaranteed to be not NULL?

> + if (bus) {
> + target = bus->self;
> + if (!target->is_pcie || target->pcie_type !=
> + PCI_EXP_TYPE_PCI_BRIDGE)
> + target = NULL;
> + }
> + if (target)
> + pci_dev_get(target);
> + }
> +
> + if (target)
> + has_dev = npme_pme_target(target);

What's the meaning of 'has_dev'? It seems to be the result of the bus type
callback.

> + else
> + printk(KERN_ERR"Can't find device %02d:%d.%d which invokes PME\n",
> + data->bdf >> 8, PCI_SLOT(data->bdf),
> + PCI_FUNC(data->bdf));
> +
> + spin_lock_irqsave(&data->lock, flags);
> + /* clear pending PME */
> + npme_clear_pme(dev->port);
> + /* reenable native PME */
> + if (!data->exit)
> + npme_enable_pme(dev->port, true);

What does data->exit different from zero mean at this point?

> +
> + spin_unlock_irqrestore(&data->lock, flags);
> +
> + if (!has_dev)
> + printk(KERN_ERR"Spurious Native PME interrupt %d received\n",
> + dev->irq);
> +
> + if (target)
> + pci_dev_put(target);
> +}
> +

Add a kerneldoc comment, please.

> +static irqreturn_t npme_irq(int irq, void *context)
> +{
> + int pos;
> + struct pci_dev *pdev;
> + u32 rtsta;
> + struct npme_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;
> + }
> +
> + data->bdf = (u16)rtsta;

Hm, couldn't we use pci_read_config_word() above instead?

> +
> + /* disable PME to avoid interrupt flood */
> + npme_enable_pme(pdev, false);
> + spin_unlock_irqrestore(&data->lock, flags);
> +
> + schedule_work(&data->work);

I'm not sure if the workqueue is exactly suitable for that. Have you
considered using anything else?

> +
> + return IRQ_HANDLED;
> +}
> +
> +#ifdef CONFIG_ACPI

Add a kerneldoc comment, please. Also, this should go into a separate file
with 'acpi' in its name IMO.

> +static int 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;
> + pcie_osc_support_set(OSC_EXT_PCI_CONFIG_SUPPORT);
> + status = pci_osc_control_set(handle,
> + OSC_PCI_EXPRESS_NATIVE_HP_CONTROL |
> + OSC_PCI_EXPRESS_CAP_STRUCTURE_CONTROL);
> +
> + if (ACPI_FAILURE(status)) {
> + printk(KERN_DEBUG "Native PME service couldn't init device "
> + "%s - %s\n", pciedev->device.bus_id,
> + (status == AE_SUPPORT || status == AE_NOT_FOUND) ?
> + "no _OSC support" : "Run ACPI _OSC fails");
> + return -EINVAL;
> + }
> +
> + return 0;
> +}
> +#else
> +static inline int npme_osc_setup(struct pcie_device *pciedev)
> +{
> + return 0;
> +}
> +#endif
> +

Add a kerneldoc comment, please.
Also, I'd call it differently, like pcie_npme_probe().

> +static int __devinit npme_probe(struct pcie_device *dev,
> + const struct pcie_port_service_id *id)
> +{
> + struct pci_dev *pdev;
> + int status;
> + struct npme_data *data;
> +
> + if (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, npme_work_handle);
> + data->dev = dev;
> + set_service_data(dev, data);
> +
> + pdev = dev->port;
> +
> + /* clear pending PME */
> + npme_clear_pme(pdev);
> +
> + status = request_irq(dev->irq, npme_irq, IRQF_SHARED, "npme", dev);

Who's going to set dev->irq?

> + if (status) {
> + kfree(data);
> + return status;
> + }
> +
> + /* enable PME interrupt */
> + npme_enable_pme(pdev, true);
> +
> + return 0;
> +}
> +
> +static void npme_remove(struct pcie_device *dev)

pcie_npme_remove() ?

> +{
> + struct pci_dev *pdev;
> + unsigned long flags;
> + struct npme_data *data = get_service_data(dev);
> +
> + pdev = dev->port;
> +
> + /* disable PME interrupt */
> + spin_lock_irqsave(&data->lock, flags);
> + data->exit = 1;
> + npme_enable_pme(pdev, false);
> + spin_unlock_irqrestore(&data->lock, flags);
> +
> + flush_scheduled_work();
> + free_irq(dev->irq, dev);
> +
> + /* clear pending PME */
> + npme_clear_pme(pdev);
> +
> + set_service_data(dev, NULL);
> + kfree(data);
> +}
> +

pcie_npme_suspend() ?

> +static int npme_suspend(struct pcie_device *dev, pm_message_t state)
> +{
> + struct pci_dev *pdev;
> + struct npme_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 */
> + npme_enable_pme(pdev, false);

Won't this cause a regression on systems that use the native PME mechanism
for wake-up (I have one of these)?

> + /* clear pending PME */
> + npme_clear_pme(pdev);
> + spin_unlock_irqrestore(&data->lock, flags);
> +
> + return 0;
> +}
> +

pcie_npme_resume() ?

> +static int npme_resume(struct pcie_device *dev)
> +{
> + struct pci_dev *pdev = dev->port;
> + unsigned long flags;
> + struct npme_data *data = get_service_data(dev);
> +
> + spin_lock_irqsave(&data->lock, flags);
> + npme_clear_pme(pdev);
> + npme_enable_pme(pdev, true);
> + spin_unlock_irqrestore(&data->lock, flags);
> +
> + return 0;
> +}
> +
> +static struct pcie_port_service_driver npme_driver = {
> + .name = "npme",
> + .id_table = &npme_id[0],
> +
> + .probe = npme_probe,
> + .remove = npme_remove,
> + .suspend = npme_suspend,
> + .resume = npme_resume,
> +};
> +
> +
> +static int __init npme_service_init(void)
> +{
> + if (disabled)
> + return -EINVAL;
> + return pcie_port_service_register(&npme_driver);
> +}
> +
> +static void __exit npme_service_exit(void)
> +{
> + pcie_port_service_unregister(&npme_driver);
> +}
> +
> +module_init(npme_service_init);
> +module_exit(npme_service_exit);
> +
> +MODULE_AUTHOR("Shaohua Li<shaohua.li@intel.com>");
> +MODULE_LICENSE("GPL");
> Index: linux/include/linux/pci_regs.h
> ===================================================================
> --- linux.orig/include/linux/pci_regs.h 2008-09-11 11:27:44.000000000 +0800
> +++ linux/include/linux/pci_regs.h 2008-09-11 11:28:39.000000000 +0800
> @@ -419,6 +419,7 @@
> #define PCI_EXP_RTCTL_CRSSVE 0x10 /* CRS Software Visibility Enable */
> #define PCI_EXP_RTCAP 30 /* Root Capabilities */
> #define PCI_EXP_RTSTA 32 /* Root Status */
> +#define PCI_EXP_RTSTA_PME 0x10000 /* PME status */
>
> /* Extended Capabilities (PCI-X 2.0 and Express) */
> #define PCI_EXT_CAP_ID(header) (header & 0x0000ffff)
>

Thanks,
Rafael