linux-kernel - Re: [PATCH V2 2/2] PCI: vmd: Use pci_host_set_default_pcie_link

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Message-ID: <CAJZ5v0hHU0oni=wMAMThCknAZgX5K0iNYLvyeAmS4fkmheLQ8w@mail.gmail.com>
Date: Fri, 22 Aug 2025 14:14:07 +0200
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: "David E. Box" <david.e.box@...ux.intel.com>
Cc: rafael@...nel.org, bhelgaas@...gle.com, vicamo.yang@...onical.com, 
	kenny@...ix.com, ilpo.jarvinen@...ux.intel.com, nirmal.patel@...ux.intel.com, 
	mani@...nel.org, linux-pm@...r.kernel.org, linux-pci@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH V2 2/2] PCI: vmd: Use pci_host_set_default_pcie_link_state()
 to set ASPM defaults

On Fri, Aug 22, 2025 at 5:12 AM David E. Box
<david.e.box@...ux.intel.com> wrote:
>
> Now that pci_host_set_default_pcie_link_state() exists, set the VMD child
> domain with PCIE_LINK_STATE_ALL at bridge creation so core ASPM uses those
> defaults during ASPM and CLKPM capability init.
>
> Also remove the unneeded pci_set_power_state_locked(pdev, PCI_D0) and
> pci_enable_link_state_locked() calls now that the links are configured
> during enumeration.
>
> This aligns VMD behavior with platform expectations without per-controller
> ASPM tweaks at runtime.
>
> Signed-off-by: David E. Box <david.e.box@...ux.intel.com>

No issues found, so

Reviewed-by: Rafael J. Wysocki (Intel) <rafael@...nel.org>

> ---
> Changes in V2:
>
>   -- Separated VMD changes into new patch.
>   -- Changed comment for VMD_FEAT_BIOS_PM_QUIRK to remove ASPM
>   -- Removed pci_set_power_state() and pci_enable_link_state_locked()
>      calls in vmd_pm_enable_quirk()
>   -- Use pci_host_set_default_pcie_link_state()
>
>  drivers/pci/controller/vmd.c | 22 ++++++++--------------
>  1 file changed, 8 insertions(+), 14 deletions(-)
>
> diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
> index b679c7f28f51..b99e01a57ddb 100644
> --- a/drivers/pci/controller/vmd.c
> +++ b/drivers/pci/controller/vmd.c
> @@ -71,10 +71,9 @@ enum vmd_features {
>         VMD_FEAT_CAN_BYPASS_MSI_REMAP           = (1 << 4),
>
>         /*
> -        * Enable ASPM on the PCIE root ports and set the default LTR of the
> -        * storage devices on platforms where these values are not configured by
> -        * BIOS. This is needed for laptops, which require these settings for
> -        * proper power management of the SoC.
> +        * Program default LTR values for storage devices on platforms where
> +        * firmware did not. Required on many laptops for proper SoC power
> +        * management.
>          */
>         VMD_FEAT_BIOS_PM_QUIRK          = (1 << 5),
>  };
> @@ -733,7 +732,7 @@ static void vmd_copy_host_bridge_flags(struct pci_host_bridge *root_bridge,
>  }
>
>  /*
> - * Enable ASPM and LTR settings on devices that aren't configured by BIOS.
> + * Enable LTR settings on devices that aren't configured by BIOS.
>   */
>  static int vmd_pm_enable_quirk(struct pci_dev *pdev, void *userdata)
>  {
> @@ -747,7 +746,7 @@ static int vmd_pm_enable_quirk(struct pci_dev *pdev, void *userdata)
>
>         pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_LTR);
>         if (!pos)
> -               goto out_state_change;
> +               return 0;
>
>         /*
>          * Skip if the max snoop LTR is non-zero, indicating BIOS has set it
> @@ -755,7 +754,7 @@ static int vmd_pm_enable_quirk(struct pci_dev *pdev, void *userdata)
>          */
>         pci_read_config_dword(pdev, pos + PCI_LTR_MAX_SNOOP_LAT, &ltr_reg);
>         if (!!(ltr_reg & (PCI_LTR_VALUE_MASK | PCI_LTR_SCALE_MASK)))
> -               goto out_state_change;
> +               return 0;
>
>         /*
>          * Set the default values to the maximum required by the platform to
> @@ -767,13 +766,6 @@ static int vmd_pm_enable_quirk(struct pci_dev *pdev, void *userdata)
>         pci_write_config_dword(pdev, pos + PCI_LTR_MAX_SNOOP_LAT, ltr_reg);
>         pci_info(pdev, "VMD: Default LTR value set by driver\n");
>
> -out_state_change:
> -       /*
> -        * Ensure devices are in D0 before enabling PCI-PM L1 PM Substates, per
> -        * PCIe r6.0, sec 5.5.4.
> -        */
> -       pci_set_power_state_locked(pdev, PCI_D0);
> -       pci_enable_link_state_locked(pdev, PCIE_LINK_STATE_ALL);
>         return 0;
>  }
>
> @@ -921,6 +913,8 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
>         WARN(sysfs_create_link(&vmd->dev->dev.kobj, &vmd->bus->dev.kobj,
>                                "domain"), "Can't create symlink to domain\n");
>
> +       pci_host_set_default_pcie_link_state(to_pci_host_bridge(vmd->bus->bridge),
> +                                            PCIE_LINK_STATE_ALL);
>         vmd_acpi_begin();
>
>         pci_scan_child_bus(vmd->bus);
> --
> 2.43.0
>