Re: [PATCH V10 0/4] Enable PCIe ASPM and LTR on select hardware

Sathyanarayanan Kuppuswamy
2023-01-20T05:35:43Z

On 1/19/23 7:15 PM, David E. Box wrote:
> This series adds a work around for enabling PCIe ASPM and for setting PCIe
> LTR values on VMD reserved root ports on select platforms. While
> configuration of these capabilities is usually done by BIOS, on these
> platforms these capabilities will not be configured because the ports are
> not visible to BIOS. This was part of an initial design that expected the
> driver to completely handle the ports, including power management. However
> on Linux those ports are still managed by the PCIe core, which has the
> expectation that they adhere to device standards including BIOS
> configuration, leading to this problem.
>
> The target platforms are Tiger Lake, Alder Lake, and Raptor Lake though the
> latter has already implemented support for configuring the LTR values.
> Meteor Lake is expected add BIOS ASPM support, eliminating the future need
> for this work around.
>
> Note, the driver programs the LTRs because BIOS would also normally do this
> for devices that do not set them by default. Without this, SoC power
> management would be blocked on those platform. This SoC specific value is
> the maximum latency required to allow the SoC to enter the deepest power
> state.
>
> This patch addresses the following open bugzillas on VMD enabled laptops
> that cannot enter low power states.
>
> 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
>

Looks good to me.

Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>

> David E. Box (3):
> PCI: vmd: Use PCI_VDEVICE in device list
> PCI: vmd: Create feature grouping for client products
> PCI: vmd: Add quirk to configure PCIe ASPM and LTR
>
> Michael Bottini (1):
> PCI/ASPM: Add pci_enable_link_state()
>
> drivers/pci/controller/vmd.c | 97 ++++++++++++++++++++++++++----------
> drivers/pci/pcie/aspm.c | 54 ++++++++++++++++++++
> include/linux/pci.h | 7 +++
> 3 files changed, 132 insertions(+), 26 deletions(-)
>
>
> base-commit: 5dc4c995db9eb45f6373a956eb1f69460e69e6d4

--
Sathyanarayanan Kuppuswamy
Linux Kernel Developer