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SubjectRe: [PATCH] PCI: Don't clear ASPM bits when the FADT declares it's unsupported
On Tue, Apr 07, 2015 at 11:07:00AM -0700, Matthew Garrett wrote:
> Communications with a hardware vendor confirm that the expected behaviour on
> systems that set the FADT ASPM disable bit but which still grant full PCIe
> control is for the OS to leave any BIOS configuration intact and refuse to
> touch the ASPM bits. This mimics the behaviour of Windows.
>
> Signed-off-by: Matthew Garrett <mjg59@coreos.com>

Applied to pci/misc for v4.1, thanks!

> ---
> drivers/acpi/pci_root.c | 19 ++++++++-----------
> drivers/pci/pcie/aspm.c | 18 ------------------
> include/linux/pci-aspm.h | 4 ----
> 3 files changed, 8 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> index 68a5f71..1b5569c 100644
> --- a/drivers/acpi/pci_root.c
> +++ b/drivers/acpi/pci_root.c
> @@ -423,8 +423,7 @@ out:
> }
> EXPORT_SYMBOL(acpi_pci_osc_control_set);
>
> -static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm,
> - int *clear_aspm)
> +static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm)
> {
> u32 support, control, requested;
> acpi_status status;
> @@ -495,10 +494,12 @@ static void negotiate_os_control(struct acpi_pci_root *root, int *no_aspm,
> decode_osc_control(root, "OS now controls", control);
> if (acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_ASPM) {
> /*
> - * We have ASPM control, but the FADT indicates
> - * that it's unsupported. Clear it.
> + * We have ASPM control, but the FADT indicates that
> + * it's unsupported. Leave existing configuration
> + * intact and prevent the OS from touching it.
> */
> - *clear_aspm = 1;
> + dev_info(&device->dev, "FADT indicates ASPM is unsupported, using BIOS configuration\n");
> + *no_aspm = 1;
> }
> } else {
> decode_osc_control(root, "OS requested", requested);
> @@ -525,7 +526,7 @@ static int acpi_pci_root_add(struct acpi_device *device,
> int result;
> struct acpi_pci_root *root;
> acpi_handle handle = device->handle;
> - int no_aspm = 0, clear_aspm = 0;
> + int no_aspm = 0;
> bool hotadd = system_state != SYSTEM_BOOTING;
>
> root = kzalloc(sizeof(struct acpi_pci_root), GFP_KERNEL);
> @@ -584,7 +585,7 @@ static int acpi_pci_root_add(struct acpi_device *device,
>
> root->mcfg_addr = acpi_pci_root_get_mcfg_addr(handle);
>
> - negotiate_os_control(root, &no_aspm, &clear_aspm);
> + negotiate_os_control(root, &no_aspm);
>
> /*
> * TBD: Need PCI interface for enumeration/configuration of roots.
> @@ -607,10 +608,6 @@ static int acpi_pci_root_add(struct acpi_device *device,
> goto remove_dmar;
> }
>
> - if (clear_aspm) {
> - dev_info(&device->dev, "Disabling ASPM (FADT indicates it is unsupported)\n");
> - pcie_clear_aspm(root->bus);
> - }
> if (no_aspm)
> pcie_no_aspm();
>
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index 820740a..7d4fcdc 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -782,24 +782,6 @@ void pci_disable_link_state(struct pci_dev *pdev, int state)
> }
> EXPORT_SYMBOL(pci_disable_link_state);
>
> -void pcie_clear_aspm(struct pci_bus *bus)
> -{
> - struct pci_dev *child;
> -
> - if (aspm_force)
> - return;
> -
> - /*
> - * Clear any ASPM setup that the firmware has carried out on this bus
> - */
> - list_for_each_entry(child, &bus->devices, bus_list) {
> - __pci_disable_link_state(child, PCIE_LINK_STATE_L0S |
> - PCIE_LINK_STATE_L1 |
> - PCIE_LINK_STATE_CLKPM,
> - false, true);
> - }
> -}
> -
> static int pcie_aspm_set_policy(const char *val, struct kernel_param *kp)
> {
> int i;
> diff --git a/include/linux/pci-aspm.h b/include/linux/pci-aspm.h
> index 8af4610..207c561 100644
> --- a/include/linux/pci-aspm.h
> +++ b/include/linux/pci-aspm.h
> @@ -29,7 +29,6 @@ void pcie_aspm_pm_state_change(struct pci_dev *pdev);
> void pcie_aspm_powersave_config_link(struct pci_dev *pdev);
> void pci_disable_link_state(struct pci_dev *pdev, int state);
> void pci_disable_link_state_locked(struct pci_dev *pdev, int state);
> -void pcie_clear_aspm(struct pci_bus *bus);
> void pcie_no_aspm(void);
> #else
> static inline void pcie_aspm_init_link_state(struct pci_dev *pdev)
> @@ -47,9 +46,6 @@ static inline void pcie_aspm_powersave_config_link(struct pci_dev *pdev)
> static inline void pci_disable_link_state(struct pci_dev *pdev, int state)
> {
> }
> -static inline void pcie_clear_aspm(struct pci_bus *bus)
> -{
> -}
> static inline void pcie_no_aspm(void)
> {
> }
> --
> 2.3.4
>


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