On Monday, March 09, 2015 03:46:01 PM Aaron Lu wrote: > An ECN meant to specify possible delay optimizations is available on > the PCI website: > https://www.pcisig.com/specifications/conventional/pci_firmware/ECN_fw_latency_optimization_final.pdf > where it has defined two functions for an UUID specified _DSM: > Function 8: If system firmware assumes the responsibility of post > Conventional Reset delay (and informs the Operating System via this DSM > function) on Sx Resume (such as boot from ACPI S5, or resume from ACPI > S4 or S3 states), the Operating System may assume sufficient time has > elapsed since the end of reset, and devices within the PCI subsystem are > ready for Configuration Access. > If the system firmware supports runtime power gating on any of the > device within PCI subsystem covered by this DSM function, the system > firmware is responsible for covering the necessary post power-on reset > delay. > > Function 9: Specify various smaller delay values than required by the > SPEC for individual PCI devices like shorter delay values after > conventional reset, D3hot to D0 transition, functional level reset, etc. > > This patch adds support for function 8 and part of function 9. For > function 8, the patch will check if the required _DSM function satisfies > the requirement and then set the per PCI device's d3cold_delay variable > to zero. For function 9, the values affecting delays after conventional > reset and D3hot->D0 are examined and the per PCI device's d3cold_delay > and d3_delay are updated if the _DSM's return value is smaller than what > the SPEC requires. > > Signed-off-by: Aaron Lu <aaron.lu@xxxxxxxxx> > --- > drivers/pci/pci-acpi.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 61 insertions(+) > > diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c > index 489063987325..c833b054c00c 100644 > --- a/drivers/pci/pci-acpi.c > +++ b/drivers/pci/pci-acpi.c > @@ -558,6 +558,64 @@ static struct acpi_device *acpi_pci_find_companion(struct device *dev) > check_children); > } > > +/** > + * pci_acpi_delay_optimize - optimize PCI D3 and D3cold delay from ACPI > + * @pdev: the PCI device whose delay is to be updated > + * @adev: the companion ACPI device of this PCI device > + * > + * Description: The word "Description" above is not necessary. > + * This function is used to update the d3_delay and d3cold_delay of a PCI I'd simply say "Update the d3_delay and d3cold_delay of a PCI device from the ACPI _DSM control method of either its own or its parent bridge." I'd add an empty line here and then the rest of the below starting with "The UUID ...". > + * device from ACPI _DSM control method of either its own or its parent > + * bridge device. The UUID of the _DSM control method, together with other > + * information like which delay values can be optimized, etc. is defined in > + * the fw_latency_optimization ECN availabe on PCIsig.com. The ECN has a number or title I suppose? > + * Function 9 of the ACPI _DSM control method, if availabe for a specific PCI > + * device, provides various possible delay values that are less than what the > + * SPEC requires. Here, we only deal with d3_delay and d3cold_delay. Others > + * can be added later. > + * Function 8 of the ACPI _DSM control method, if availabe for a specific PCI > + * bridge, means all its children devices do not need the reset delay when > + * leaving from D3cold state. > + */ > +static void pci_acpi_delay_optimize(struct pci_dev *pdev, struct acpi_device *adev) > +{ > + const u8 uuid[] = { > + 0xd0, 0x37, 0xc9, 0xe5, 0x53, 0x35, 0x7a, 0x4d, > + 0x91, 0x17, 0xea, 0x4d, 0x19, 0xc3, 0x43, 0x4d > + }; > + int revision = 3, function = 9, value; > + acpi_handle handle = adev->handle; > + union acpi_object *obj, *elements; > + > + obj = acpi_evaluate_dsm(handle, uuid, revision, function, NULL); > + if (obj) { > + if (obj->type == ACPI_TYPE_PACKAGE && obj->package.count == 5) { > + elements = obj->package.elements; > + if (elements[3].type == ACPI_TYPE_INTEGER) { > + value = (int)elements[3].integer.value / 1000; > + if (value < PCI_PM_D3_WAIT) > + pdev->d3_delay = value; > + } > + if (elements[0].type == ACPI_TYPE_INTEGER) { > + value = (int)elements[0].integer.value / 1000; > + if (value < PCI_PM_D3COLD_WAIT) > + pdev->d3cold_delay = value; > + } > + } > + kfree(obj); > + } > + > + function = 8; > + handle = ACPI_HANDLE(pdev->bus->bridge); > + obj = acpi_evaluate_dsm(handle, uuid, revision, function, NULL); > + if (!obj) > + return; > + > + if (obj->type == ACPI_TYPE_INTEGER && obj->integer.value == 1) > + pdev->d3cold_delay = 0; > + kfree(obj); > +} > + > static void pci_acpi_setup(struct device *dev) > { > struct pci_dev *pci_dev = to_pci_dev(dev); > @@ -566,6 +624,9 @@ static void pci_acpi_setup(struct device *dev) > if (!adev) > return; > > + if (pci_dev->pm_cap) > + pci_acpi_delay_optimize(pci_dev, adev); > + > pci_acpi_add_pm_notifier(adev, pci_dev); > if (!adev->wakeup.flags.valid) > return; > -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
