Hi Mario, On Tue, Oct 10, 2023 at 6:57 AM Mario Limonciello <mario.limonciello@xxxxxxx> wrote: > > The default kernel policy will allow modern machines to effectively put > all PCIe bridges into PCI D3. This policy doesn't match what Windows uses. > > In Windows the driver stack includes a "Power Engine Plugin" (uPEP driver) > to decide the policy for integrated devices using PEP device constraints. > > Device constraints are expressed as a number in the _DSM of the PNP0D80 > device and exported by the kernel in acpi_get_lps0_constraint(). > > Add support for SoCs to use constraints on Linux as well for deciding > target state for integrated PCI bridges. > > No SoCs are introduced by default with this change, they will be added > later on a case by case basis. > > Link: https://learn.microsoft.com/en-us/windows-hardware/design/device-experiences/platform-design-for-modern-standby#low-power-core-silicon-cpu-soc-dram > Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx> > --- > drivers/platform/x86/amd/pmc/pmc.c | 59 ++++++++++++++++++++++++++++++ > 1 file changed, 59 insertions(+) > > diff --git a/drivers/platform/x86/amd/pmc/pmc.c b/drivers/platform/x86/amd/pmc/pmc.c > index c1e788b67a74..34e76c6b3fb2 100644 > --- a/drivers/platform/x86/amd/pmc/pmc.c > +++ b/drivers/platform/x86/amd/pmc/pmc.c > @@ -570,6 +570,14 @@ static void amd_pmc_dbgfs_unregister(struct amd_pmc_dev *dev) > debugfs_remove_recursive(dev->dbgfs_dir); > } > > +static bool amd_pmc_use_acpi_constraints(struct amd_pmc_dev *dev) > +{ > + switch (dev->cpu_id) { > + default: > + return false; > + } > +} > + > static bool amd_pmc_is_stb_supported(struct amd_pmc_dev *dev) > { > switch (dev->cpu_id) { > @@ -741,6 +749,41 @@ static int amd_pmc_czn_wa_irq1(struct amd_pmc_dev *pdev) > return 0; > } > > +/* > + * Constraints are specified in the ACPI LPS0 device and specify what the > + * platform intended for the device. > + * > + * If a constraint is present and >= to ACPI_STATE_S3, then enable D3 for the > + * device. > + * If a constraint is not present or < ACPI_STATE_S3, then disable D3 for the > + * device. > + */ > +static enum bridge_d3_pref amd_pmc_d3_check(struct pci_dev *pci_dev) > +{ > + struct acpi_device *adev = ACPI_COMPANION(&pci_dev->dev); > + int constraint; > + > + if (!adev) > + return BRIDGE_PREF_UNSET; > + > + constraint = acpi_get_lps0_constraint(adev); > + dev_dbg(&pci_dev->dev, "constraint is %d\n", constraint); > + > + switch (constraint) { > + case ACPI_STATE_UNKNOWN: > + case ACPI_STATE_S0: > + case ACPI_STATE_S1: > + case ACPI_STATE_S2: I believe it's a typo? I think ACPI_STATE_Dx should be used for device state. > + return BRIDGE_PREF_DRIVER_D0; > + case ACPI_STATE_S3: > + return BRIDGE_PREF_DRIVER_D3; I've seen both 3 (i.e. ACPI_STATE_D3_HOT) and 4 (i.e. ACPI_STATE_D3_COLD) defined in LPI constraint table. Should those two be treated differently? > + default: > + break; > + } > + > + return BRIDGE_PREF_UNSET; > +} > + > static int amd_pmc_verify_czn_rtc(struct amd_pmc_dev *pdev, u32 *arg) > { > struct rtc_device *rtc_device; > @@ -881,6 +924,11 @@ static struct acpi_s2idle_dev_ops amd_pmc_s2idle_dev_ops = { > .restore = amd_pmc_s2idle_restore, > }; > > +static struct pci_d3_driver_ops amd_pmc_d3_ops = { > + .check = amd_pmc_d3_check, > + .priority = 50, > +}; > + > static int amd_pmc_suspend_handler(struct device *dev) > { > struct amd_pmc_dev *pdev = dev_get_drvdata(dev); > @@ -1074,10 +1122,19 @@ static int amd_pmc_probe(struct platform_device *pdev) > amd_pmc_quirks_init(dev); > } > > + if (amd_pmc_use_acpi_constraints(dev)) { > + err = pci_register_driver_d3_policy_cb(&amd_pmc_d3_ops); > + if (err) > + goto err_register_lps0; > + } Does this only apply to PCI? USB can have ACPI companion too. Kai-Heng > + > amd_pmc_dbgfs_register(dev); > pm_report_max_hw_sleep(U64_MAX); > return 0; > > +err_register_lps0: > + if (IS_ENABLED(CONFIG_SUSPEND)) > + acpi_unregister_lps0_dev(&amd_pmc_s2idle_dev_ops); > err_pci_dev_put: > pci_dev_put(rdev); > return err; > @@ -1089,6 +1146,8 @@ static void amd_pmc_remove(struct platform_device *pdev) > > if (IS_ENABLED(CONFIG_SUSPEND)) > acpi_unregister_lps0_dev(&amd_pmc_s2idle_dev_ops); > + if (amd_pmc_use_acpi_constraints(dev)) > + pci_unregister_driver_d3_policy_cb(&amd_pmc_d3_ops); > amd_pmc_dbgfs_unregister(dev); > pci_dev_put(dev->rdev); > mutex_destroy(&dev->lock); > -- > 2.34.1 >
