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Date: Fri, 18 Nov 2022 21:50:21 -0800
From: Sathyanarayanan Kuppuswamy
<sathyanarayanan.kuppuswamy@...ux.intel.com>
To: "David E. Box" <david.e.box@...ux.intel.com>,
nirmal.patel@...ux.intel.com, jonathan.derrick@...ux.dev,
lorenzo.pieralisi@....com, hch@...radead.org, kw@...ux.com,
robh@...nel.org, bhelgaas@...gle.com, michael.a.bottini@...el.com,
rafael@...nel.org, me@...ityamohan.in
Cc: linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V8 RESEND 4/4] PCI: vmd: Add quirk to configure PCIe ASPM
and LTR
HI,
On 11/18/22 6:14 PM, David E. Box wrote:
> PCIe ports reserved for VMD use are not visible to BIOS and therefore not
> configured to enable PCIe ASPM or LTR values (which BIOS will configure if
> they are not set). Lack of this programming results in high power
> consumption on laptops as reported in bugzilla. For affected products use
> pci_enable_link_state to set the allowed link states for devices on the
> root ports. Also set the LTR value to the maximum value needed for the SoC.
>
> This is a workaround for products from Rocket Lake through Alder Lake.
> Raptor Lake, the latest product at this time, has already implemented LTR
> configuring in BIOS. Future products will move ASPM configuration back to
> BIOS as well. As this solution is intended for laptops, support is not
> added for hotplug or for devices downstream of a switch on the root port.
>
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=212355
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=215063
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=213717
>
> Signed-off-by: Michael Bottini <michael.a.bottini@...ux.intel.com>
> Signed-off-by: David E. Box <david.e.box@...ux.intel.com>
> Reviewed-by: Jon Derrick <jonathan.derrick@...ux.dev>
> Reviewed-by: Nirmal Patel <nirmal.patel@...ux.intel.com>
> ---
> V8
> - Removed struct vmd_device_data patch. Instead use #define for the LTR
> value which is the same across all products needing the quirk.
> V7
> - No change
> V6
> - Set ASPM first before setting LTR. This is needed because some
> devices may only have LTR set by BIOS and not ASPM
> - Skip setting the LTR if the current LTR in non-zero.
> V5
> - Provide the LTR value as driver data.
> - Use DWORD for the config space write to avoid PCI WORD access bug.
> - Set ASPM links firsts, enabling all link states, before setting a
> default LTR if the capability is present
> - Add kernel message that VMD is setting the device LTR.
> V4
> - Refactor vmd_enable_apsm() to exit early, making the lines shorter
> and more readable. Suggested by Christoph.
> V3
> - No changes
> V2
> - Use return status to print pci_info message if ASPM cannot be enabled.
> - Add missing static declaration, caught by lkp@...el.com
>
> drivers/pci/controller/vmd.c | 64 ++++++++++++++++++++++++++++++++----
> 1 file changed, 58 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/pci/controller/vmd.c b/drivers/pci/controller/vmd.c
> index 86f3085db014..cba57e3091f6 100644
> --- a/drivers/pci/controller/vmd.c
> +++ b/drivers/pci/controller/vmd.c
> @@ -66,12 +66,22 @@ enum vmd_features {
> * interrupt handling.
> */
> 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.
> + */
> + VMD_FEAT_BIOS_PM_QUIRK = (1 << 5),
> };
>
> #define VMD_FEATS_CLIENT (VMD_FEAT_HAS_MEMBAR_SHADOW_VSCAP | \
> VMD_FEAT_HAS_BUS_RESTRICTIONS | \
> VMD_FEAT_OFFSET_FIRST_VECTOR)
>
> +#define VMD_BIOS_PM_QUIRK_LTR 0x1003 /* 3145728 ns */
> +
> static DEFINE_IDA(vmd_instance_ida);
>
> /*
> @@ -713,6 +723,46 @@ static void vmd_copy_host_bridge_flags(struct pci_host_bridge *root_bridge,
> vmd_bridge->native_dpc = root_bridge->native_dpc;
> }
>
> +/*
> + * Enable ASPM and LTR settings on devices that aren't configured by BIOS.
> + */
> +static int vmd_pm_enable_quirk(struct pci_dev *pdev, void *userdata)
> +{
> + unsigned long features = *(unsigned long *)userdata;
> + u16 ltr = VMD_BIOS_PM_QUIRK_LTR;
> + u32 ltr_reg;
> + int pos;
> +
> + if (!(features & VMD_FEAT_BIOS_PM_QUIRK))
> + return 0;
> +
> + pci_enable_link_state(pdev, PCIE_LINK_STATE_ALL);
> +
> + pos = pci_find_ext_capability(pdev, PCI_EXT_CAP_ID_LTR);
> + if (!pos)
> + return 0;
> +
> + /*
> + * Skip if the max snoop LTR is non-zero, indicating BIOS has set it
> + * so the LTR quirk is not needed.
> + */
> + pci_read_config_dword(pdev, pos + PCI_LTR_MAX_SNOOP_LAT, <r_reg);
> + if (!!(ltr_reg & (PCI_LTR_VALUE_MASK | PCI_LTR_SCALE_MASK)))
> + return 0;
> +
> + /*
> + * Set the default values to the maximum required by the platform to
> + * allow the deepest power management savings. Write as a DWORD where
> + * the lower word is the max snoop latency and the upper word is the
> + * max non-snoop latency.
> + */
> + ltr_reg = (ltr << 16) | ltr;
> + pci_write_config_dword(pdev, pos + PCI_LTR_MAX_SNOOP_LAT, ltr_reg);
> + pci_info(pdev, "VMD: Default LTR value set by driver\n");
> +
> + return 0;
> +}
> +
> static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
> {
> struct pci_sysdata *sd = &vmd->sysdata;
> @@ -867,6 +917,8 @@ static int vmd_enable_domain(struct vmd_dev *vmd, unsigned long features)
> pci_reset_bus(child->self);
> pci_assign_unassigned_bus_resources(vmd->bus);
>
> + pci_walk_bus(vmd->bus, vmd_pm_enable_quirk, &features);
> +
> /*
> * VMD root buses are virtual and don't return true on pci_is_pcie()
> * and will fail pcie_bus_configure_settings() early. It can instead be
> @@ -1005,17 +1057,17 @@ static const struct pci_device_id vmd_ids[] = {
> VMD_FEAT_HAS_BUS_RESTRICTIONS |
> VMD_FEAT_CAN_BYPASS_MSI_REMAP,},
> {PCI_VDEVICE(INTEL, 0x467f),
> - .driver_data = VMD_FEATS_CLIENT,},
> + .driver_data = VMD_FEATS_CLIENT | VMD_FEAT_BIOS_PM_QUIRK,},
> {PCI_VDEVICE(INTEL, 0x4c3d),
> - .driver_data = VMD_FEATS_CLIENT,},
> + .driver_data = VMD_FEATS_CLIENT | VMD_FEAT_BIOS_PM_QUIRK,},
> {PCI_VDEVICE(INTEL, 0xa77f),
> - .driver_data = VMD_FEATS_CLIENT,},
> + .driver_data = VMD_FEATS_CLIENT | VMD_FEAT_BIOS_PM_QUIRK,},
> {PCI_VDEVICE(INTEL, 0x7d0b),
> - .driver_data = VMD_FEATS_CLIENT,},
> + .driver_data = VMD_FEATS_CLIENT | VMD_FEAT_BIOS_PM_QUIRK,},
> {PCI_VDEVICE(INTEL, 0xad0b),
> - .driver_data = VMD_FEATS_CLIENT,},
> + .driver_data = VMD_FEATS_CLIENT | VMD_FEAT_BIOS_PM_QUIRK,},
> {PCI_VDEVICE(INTEL, PCI_DEVICE_ID_INTEL_VMD_9A0B),
> - .driver_data = VMD_FEATS_CLIENT,},
> + .driver_data = VMD_FEATS_CLIENT | VMD_FEAT_BIOS_PM_QUIRK,},
Why not add VMD_FEAT_BIOS_PM_QUIRK part of VMD_FEATS_CLIENT?
> {0,}
> };
> MODULE_DEVICE_TABLE(pci, vmd_ids);
--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer
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