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Commit f492edb4 authored by David E. Box's avatar David E. Box Committed by Lorenzo Pieralisi
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PCI: vmd: Add quirk to configure PCIe ASPM and LTR



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

Link: https://lore.kernel.org/r/20230120031522.2304439-5-david.e.box@linux.intel.com
Signed-off-by: default avatarMichael Bottini <michael.a.bottini@linux.intel.com>
Signed-off-by: default avatarDavid E. Box <david.e.box@linux.intel.com>
Signed-off-by: default avatarLorenzo Pieralisi <lpieralisi@kernel.org>
Reviewed-by: default avatarJon Derrick <jonathan.derrick@linux.dev>
Reviewed-by: default avatarNirmal Patel <nirmal.patel@linux.intel.com>
Reviewed-by: default avatarKuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
parent 14d2079a
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