[+cc Heiner]
On Thu, Aug 08, 2019 at 11:55:07PM +0200, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
>
> Add a function checking whether or not PCIe ASPM has been enabled for
> a given device.
>
> It will be used by the NVMe driver to decide how to handle the
> device during system suspend.
>
> Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
> ---
>
> v2 -> v3:
> * Make the new function return bool.
> * Change its name back to pcie_aspm_enabled().
> * Fix kerneldoc comment formatting.
>
> -> v2:
> * Move the PCI/PCIe ASPM changes to a separate patch.
> * Add the _mask suffix to the new function name.
> * Add EXPORT_SYMBOL_GPL() to the new function.
> * Avoid adding an unnecessary blank line.
>
> ---
> drivers/pci/pcie/aspm.c | 20 ++++++++++++++++++++
> include/linux/pci.h | 3 +++
> 2 files changed, 23 insertions(+)
>
> Index: linux-pm/drivers/pci/pcie/aspm.c
> ===================================================================
> --- linux-pm.orig/drivers/pci/pcie/aspm.c
> +++ linux-pm/drivers/pci/pcie/aspm.c
> @@ -1170,6 +1170,26 @@ static int pcie_aspm_get_policy(char *bu
> module_param_call(policy, pcie_aspm_set_policy, pcie_aspm_get_policy,
> NULL, 0644);
>
> +/**
> + * pcie_aspm_enabled - Check if PCIe ASPM has been enabled for a device.
> + * @pci_device: Target device.
> + */
> +bool pcie_aspm_enabled(struct pci_dev *pci_device)
> +{
> + struct pci_dev *bridge = pci_upstream_bridge(pci_device);
> + bool ret;
> +
> + if (!bridge)
> + return false;
> +
> + mutex_lock(&aspm_lock);
> + ret = bridge->link_state ? !!bridge->link_state->aspm_enabled : false;
> + mutex_unlock(&aspm_lock);
Why do we need to acquire aspm_lock here? We aren't modifying
anything, and I don't think we're preventing a race. If this races
with another thread that changes aspm_enabled, we'll return either the
old state or the new one, and I think that's still the case even if we
don't acquire aspm_lock.
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(pcie_aspm_enabled);
> +
> #ifdef CONFIG_PCIEASPM_DEBUG
> static ssize_t link_state_show(struct device *dev,
> struct device_attribute *attr,
> Index: linux-pm/include/linux/pci.h
> ===================================================================
> --- linux-pm.orig/include/linux/pci.h
> +++ linux-pm/include/linux/pci.h
> @@ -1567,8 +1567,11 @@ extern bool pcie_ports_native;
>
> #ifdef CONFIG_PCIEASPM
> bool pcie_aspm_support_enabled(void);
> +bool pcie_aspm_enabled(struct pci_dev *pci_device);
> #else
> static inline bool pcie_aspm_support_enabled(void) { return false; }
> +static inline bool pcie_aspm_enabled(struct pci_dev *pci_device)
> +{ return false; }
> #endif
>
> #ifdef CONFIG_PCIEAER
>
>
>
