The PCI firmware specification includes support for a _DSM function to specify a PERST# assertion delay. "The Add PERST# Assertion Delay function is used to convey the requirement for a fixed delay in timing between the time the PME_TO_Ack message is received at the PCI Express Downstream Port that originated the PME_Turn_Off message, and the time the platform asserts PERST# to the slot during the corresponding Endpoint’s or PCI Express Upstream Port’s transition to D3cold while the system is in an ACPI operational state." Add API for callers to utilize this _DSM. Link: https://members.pcisig.com/wg/PCI-SIG/document/15350 PCI Firmware specification 3.3, section 4.6.11 Signed-off-by: Mario Limonciello <mario.limonciello@xxxxxxx> --- drivers/pci/pci-acpi.c | 40 ++++++++++++++++++++++++++++++++++++++++ include/linux/pci-acpi.h | 2 ++ 2 files changed, 42 insertions(+) diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c index 257858a6719e..82e04808040d 100644 --- a/drivers/pci/pci-acpi.c +++ b/drivers/pci/pci-acpi.c @@ -1402,6 +1402,46 @@ int pci_acpi_request_aux_power_for_d3cold(struct pci_dev *pdev, int arg) } EXPORT_SYMBOL_GPL(pci_acpi_request_aux_power_for_d3cold); +/** + * pci_acpi_set_perst_delay - Set the assertion delay for the PERST# signal + * @pdev: PCI device to set the delay for + * @arg: Delay value in microseconds + * + * This function sets the delay for the PERST# signal of the given PCI device. + * The delay value is specified in microseconds through the @arg parameter. + * The maximum delay value is 10000 microseconds. + * + * Return: 0 on success, negative error code on failure + */ +int pci_acpi_set_perst_delay(struct pci_dev *pdev, int arg) +{ + struct acpi_device *adev = ACPI_COMPANION(&pdev->dev); + union acpi_object *obj; + union acpi_object argv4 = { + .integer.type = ACPI_TYPE_INTEGER, + .integer.value = arg, + }; + int val; + + if (!acpi_check_dsm(adev->handle, &pci_acpi_dsm_guid, + pci_acpi_dsm_rev, 1 << DSM_PCI_ADD_PERST_DELAY)) + return -ENODEV; + + if (arg > 10000) + return -EINVAL; + + obj = acpi_evaluate_dsm_typed(adev->handle, &pci_acpi_dsm_guid, + pci_acpi_dsm_rev, DSM_PCI_ADD_PERST_DELAY, + &argv4, ACPI_TYPE_INTEGER); + if (!obj) + return -EIO; + + val = obj->integer.value; + ACPI_FREE(obj); + return (val == arg) ? 0 : -EINVAL; +} +EXPORT_SYMBOL_GPL(pci_acpi_set_perst_delay); + /** * pci_acpi_optimize_delay - optimize PCI D3 and D3cold delay from ACPI * @pdev: the PCI device whose delay is to be updated diff --git a/include/linux/pci-acpi.h b/include/linux/pci-acpi.h index bc6372bcb7d6..bdce83c3afbf 100644 --- a/include/linux/pci-acpi.h +++ b/include/linux/pci-acpi.h @@ -123,12 +123,14 @@ extern const int pci_acpi_dsm_rev; #define DSM_PCI_POWER_ON_RESET_DELAY 0x08 #define DSM_PCI_DEVICE_READINESS_DURATIONS 0x09 #define DSM_PCI_REQUEST_D3COLD_AUX_POWER 0x0A +#define DSM_PCI_ADD_PERST_DELAY 0x0B #define PCI_D3COLD_AUX_DENIED 0 #define PCI_D3COLD_AUX_GRANTED 1 #define PCI_D3COLD_AUX_NO_MAIN_POWER_REMOVAL 2 int pci_acpi_request_aux_power_for_d3cold(struct pci_dev *pdev, int arg); +int pci_acpi_set_perst_delay(struct pci_dev *pdev, int arg); #ifdef CONFIG_PCIE_EDR void pci_acpi_add_edr_notifier(struct pci_dev *pdev); -- 2.34.1
