On Tue, Jun 18, 2019 at 11:13:48PM +0200, Heiner Kallweit wrote:
> Drivers may rely on pci_disable_link_state() having disabled certain
> ASPM link states. If OS can't control ASPM then pci_disable_link_state()
> turns into a no-op w/o informing the caller. The driver therefore may
> falsely assume the respective ASPM link states are disabled.
> Let pci_disable_link_state() propagate errors to the caller, enabling
> the caller to react accordingly.
>
> Signed-off-by: Heiner Kallweit <hkallweit1@xxxxxxxxx>
Acked-by: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Thanks, I think this makes good sense.
> ---
> drivers/pci/pcie/aspm.c | 20 +++++++++++---------
> include/linux/pci-aspm.h | 7 ++++---
> 2 files changed, 15 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index fd4cb7508..e44af7f4d 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -1062,18 +1062,18 @@ void pcie_aspm_powersave_config_link(struct pci_dev *pdev)
> up_read(&pci_bus_sem);
> }
>
> -static void __pci_disable_link_state(struct pci_dev *pdev, int state, bool sem)
> +static int __pci_disable_link_state(struct pci_dev *pdev, int state, bool sem)
> {
> struct pci_dev *parent = pdev->bus->self;
> struct pcie_link_state *link;
>
> if (!pci_is_pcie(pdev))
> - return;
> + return 0;
>
> if (pdev->has_secondary_link)
> parent = pdev;
> if (!parent || !parent->link_state)
> - return;
> + return -EINVAL;
>
> /*
> * A driver requested that ASPM be disabled on this device, but
> @@ -1085,7 +1085,7 @@ static void __pci_disable_link_state(struct pci_dev *pdev, int state, bool sem)
> */
> if (aspm_disabled) {
> pci_warn(pdev, "can't disable ASPM; OS doesn't have ASPM control\n");
> - return;
> + return -EPERM;
> }
>
> if (sem)
> @@ -1105,11 +1105,13 @@ static void __pci_disable_link_state(struct pci_dev *pdev, int state, bool sem)
> mutex_unlock(&aspm_lock);
> if (sem)
> up_read(&pci_bus_sem);
> +
> + return 0;
> }
>
> -void pci_disable_link_state_locked(struct pci_dev *pdev, int state)
> +int pci_disable_link_state_locked(struct pci_dev *pdev, int state)
> {
> - __pci_disable_link_state(pdev, state, false);
> + return __pci_disable_link_state(pdev, state, false);
> }
> EXPORT_SYMBOL(pci_disable_link_state_locked);
>
> @@ -1117,14 +1119,14 @@ EXPORT_SYMBOL(pci_disable_link_state_locked);
> * pci_disable_link_state - Disable device's link state, so the link will
> * never enter specific states. Note that if the BIOS didn't grant ASPM
> * control to the OS, this does nothing because we can't touch the LNKCTL
> - * register.
> + * register. Returns 0 or a negative errno.
> *
> * @pdev: PCI device
> * @state: ASPM link state to disable
> */
> -void pci_disable_link_state(struct pci_dev *pdev, int state)
> +int pci_disable_link_state(struct pci_dev *pdev, int state)
> {
> - __pci_disable_link_state(pdev, state, true);
> + return __pci_disable_link_state(pdev, state, true);
> }
> EXPORT_SYMBOL(pci_disable_link_state);
>
> diff --git a/include/linux/pci-aspm.h b/include/linux/pci-aspm.h
> index df28af5ce..67064145d 100644
> --- a/include/linux/pci-aspm.h
> +++ b/include/linux/pci-aspm.h
> @@ -24,11 +24,12 @@
> #define PCIE_LINK_STATE_CLKPM 4
>
> #ifdef CONFIG_PCIEASPM
> -void pci_disable_link_state(struct pci_dev *pdev, int state);
> -void pci_disable_link_state_locked(struct pci_dev *pdev, int state);
> +int pci_disable_link_state(struct pci_dev *pdev, int state);
> +int pci_disable_link_state_locked(struct pci_dev *pdev, int state);
> void pcie_no_aspm(void);
> #else
> -static inline void pci_disable_link_state(struct pci_dev *pdev, int state) { }
> +static inline int pci_disable_link_state(struct pci_dev *pdev, int state)
> +{ return 0; }
> static inline void pcie_no_aspm(void) { }
> #endif
>
> --
> 2.22.0
>
>
