On Tue, Mar 24, 2015 at 05:04:58PM +0800, Aaron Lu wrote: > On 03/23/2015 11:09 PM, Bjorn Helgaas wrote: > > The ECN says this function is in a host bridge scope and applies to the > > PCI subsystem beneath the bridge. This code does not map well to that > > because: > > > > 1) It evaluates _DSM more times than necessary (we only need to do it > > once per host bridge, and this does it once for every PCI device > > immediately below a host brige). > > > > 2) The settings are only applied to immediate children of the host > > bridge, not to devices deeper in the hierarchy. > > > > 3) A reader of the ECN will expect the corresponding code to be in the > > host bridge driver (pci_root.c) where we deal with other host bridge > > properties, not in per-PCI device code like this. > > > > 4) The ECN is not explicit about this, but if both function 8 (which > > applies to a whole hierarchy) and function 9 (which applies to a single > > PCI device) are implemented for the same PCI device, I would expect > > function 9 to take precedence over function 8. This patch does the > > reverse, since function 8 will overwrite any d3cold_delay that was set > > above by function 9. > > I tried to do this in drivers/acpi/pci_root.c, but didn't find a proper > way to pass this information down during PCI device scan time. So > instead, I did it in the pci root bus add time: acpi_pci_add_bus, which > is used by both the x86 code and ia64 code. Suggestions are welcome and > appreciated. > > > From 05b625d2444d90e37392dd835a97c0b582fd221f Mon Sep 17 00:00:00 2001 > From: Aaron Lu <aaron.lu@xxxxxxxxx> > Date: Fri, 14 Nov 2014 16:56:43 +0800 > Subject: [PATCH v2 2/2] PCI / ACPI: PCI delay optimization from ACPI > > 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 patche 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 all the host bus' immediate children PCI device's > d3cold_delay variable will be updated 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. Function 9's value > takes precedence over function 8. > > Signed-off-by: Aaron Lu <aaron.lu@xxxxxxxxx> > --- > drivers/pci/pci-acpi.c | 65 ++++++++++++++++++++++++++++++++++++++++++++++++ > include/linux/pci-acpi.h | 2 ++ > include/linux/pci.h | 1 + > 3 files changed, 68 insertions(+) > > diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c > index e0afc94aca01..220371c2def4 100644 > --- a/drivers/pci/pci-acpi.c > +++ b/drivers/pci/pci-acpi.c > @@ -537,11 +537,24 @@ static struct pci_platform_pm_ops acpi_pci_platform_pm = { > > void acpi_pci_add_bus(struct pci_bus *bus) > { > + union acpi_object *obj; > + > if (acpi_pci_disabled || !bus->bridge) > return; > > acpi_pci_slot_enumerate(bus); > acpiphp_enumerate_slots(bus); > + > + /* > + * For a host bridge, check its _DSM for function 8 and if > + * that is available, mark it in the corresponding pci_bus. > + */ > + if (bus->bridge->parent) > + return; This is not really an obvious way of testing for a host bridge. I think pci_is_root_bus() would be a better way, but I'm still hoping for something in pci_root.c instead. There is find_pci_host_bridge(), which might be useful (it's currently static but we might want to rename and export it for this and other reasons). > + obj = acpi_evaluate_dsm(ACPI_HANDLE(bus->bridge), pci_acpi_dsm_uuid, 3, > + RESET_DELAY_DSM, NULL); > + if (obj && obj->type == ACPI_TYPE_INTEGER && obj->integer.value == 1) > + bus->ignore_reset_delay = 1; I think you need to free "obj" here. Other acpi_evaluate_dsm() callers use ACPI_FREE(). > } > > void acpi_pci_remove_bus(struct pci_bus *bus) > @@ -567,6 +580,55 @@ 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 > + * > + * 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. > + * > + * The UUID of the _DSM control method, together with other information like > + * which delay values can be optimized, etc. is defined in a ECN available on > + * PCIsig.com titled as: ACPI additions for FW latency optimizations. > + * Function 9 of the ACPI _DSM control method, if available 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 available for the PCI host > + * bridge(reflected by the bus' ignore_reset_delay filed), 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, > + acpi_handle handle) > +{ > + int value; > + union acpi_object *obj, *elements; > + > + if (pdev->bus->ignore_reset_delay) > + pdev->d3cold_delay = 0; I think this only propagates the function 8 result to the immediate children of the host bridge, i.e., devices on the root bus. But the ECN says it affects the entire hierarchy. Can you put the ignore_reset_delay bit in the struct pci_host_bridge instead? > + > + obj = acpi_evaluate_dsm(handle, pci_acpi_dsm_uuid, 3, > + FUNCTION_DELAY_DSM, NULL); > + if (!obj) > + return; > + > + if (obj->type == ACPI_TYPE_PACKAGE && obj->package.count == 5) { > + elements = obj->package.elements; > + if (elements[0].type == ACPI_TYPE_INTEGER) { > + value = (int)elements[0].integer.value / 1000; > + if (value < PCI_PM_D3COLD_WAIT) > + pdev->d3cold_delay = value; > + } > + if (elements[3].type == ACPI_TYPE_INTEGER) { > + value = (int)elements[3].integer.value / 1000; > + if (value < PCI_PM_D3_WAIT) > + pdev->d3_delay = value; > + } > + } > + kfree(obj); > +} > + > static void pci_acpi_setup(struct device *dev) > { > struct pci_dev *pci_dev = to_pci_dev(dev); > @@ -575,6 +637,9 @@ static void pci_acpi_setup(struct device *dev) > if (!adev) > return; > > + if (pci_dev->pm_cap) > + pci_acpi_delay_optimize(pci_dev, adev->handle); Is the "pm_cap" test really necessary? If we do it this way, we then have to convince ourselves that pdev->d3cold_delay and pdev->d3_delay are only needed when pdev has a pm_cap. If we *always* fill in the delay values, it's possible they won't be used, but we don't have to prove any connection between them and a pm_cap, so the code is easier to analyze. > + > pci_acpi_add_pm_notifier(adev, pci_dev); > if (!adev->wakeup.flags.valid) > return; > diff --git a/include/linux/pci-acpi.h b/include/linux/pci-acpi.h > index 3801c704a945..a965efa52152 100644 > --- a/include/linux/pci-acpi.h > +++ b/include/linux/pci-acpi.h > @@ -79,6 +79,8 @@ static inline void acpiphp_check_host_bridge(struct acpi_device *adev) { } > > extern const u8 pci_acpi_dsm_uuid[]; > #define DEVICE_LABEL_DSM 0x07 > +#define RESET_DELAY_DSM 0x08 > +#define FUNCTION_DELAY_DSM 0x09 > > #else /* CONFIG_ACPI */ > static inline void acpi_pci_add_bus(struct pci_bus *bus) { } > diff --git a/include/linux/pci.h b/include/linux/pci.h > index a379513bddef..1e56c464d058 100644 > --- a/include/linux/pci.h > +++ b/include/linux/pci.h > @@ -471,6 +471,7 @@ struct pci_bus { > struct bin_attribute *legacy_io; /* legacy I/O for this bus */ > struct bin_attribute *legacy_mem; /* legacy mem */ > unsigned int is_added:1; > + unsigned int ignore_reset_delay:1; > }; > > #define to_pci_bus(n) container_of(n, struct pci_bus, dev) > -- > 2.1.0 > > -- > 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 -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
