linux-kernel - Re: [PATCH V6 0/3] PCI: vmd: Enable PCIe ASPM and LTR

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Date:   Tue, 1 Mar 2022 12:19:26 -0700
From:   Jonathan Derrick <jonathan.derrick@...ux.dev>
To:     "David E. Box" <david.e.box@...ux.intel.com>,
        nirmal.patel@...ux.intel.com, lorenzo.pieralisi@....com,
        hch@...radead.org, kw@...ux.com, robh@...nel.org,
        bhelgaas@...gle.com, michael.a.bottini@...ux.intel.com,
        rafael@...nel.org, me@...ityamohan.in
Cc:     linux-pci@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH V6 0/3] PCI: vmd: Enable PCIe ASPM and LTR

Set looks good to me
Thanks!

Reviewed-by: Jon Derrick <jonathan.derrick@...ux.dev>

On 2/28/2022 9:19 PM, David E. Box wrote:
> This series adds support for enabling PCIe ASPM and for setting PCIe LTR
> values on devices on root ports reserved by VMD. Configuration of these
> capabilities is usually done by BIOS. But for VMD ports these capabilities
> will not be configured because those ports are not visible to BIOS. For
> future products, post Alder Lake, the hardware team has agreed to do this
> enabling in BIOS.  But this will not apply to current products, so this
> work around is provided for them. Without this, laptops running in VMD mode
> will not be able to power gate roots ports, resulting in higher power
> consumption.
> 
> Since V4 we have more information from the BIOS team as to why BIOS
> needs to program device LTRs. This is something that should be done by
> devices, but there are many that don't provide LTR values causing them
> to block SoC level power management. BIOS sets an initial default LTR to
> account for such devices. This SoC specific value is the maximum latency
> required to allow the SoC to enter the deepest power state.
> 
> David E. Box (2):
>    PCI: vmd: Add vmd_device_data
>    PCI: vmd: Configure PCIe ASPM and LTR
> 
> Michael Bottini (1):
>    PCI/ASPM: Add ASPM BIOS override function
> 
>   drivers/pci/controller/vmd.c | 134 ++++++++++++++++++++++++++++-------
>   drivers/pci/pcie/aspm.c      |  54 ++++++++++++++
>   include/linux/pci.h          |   7 ++
>   3 files changed, 169 insertions(+), 26 deletions(-)
> 
> 
> base-commit: 754e0b0e35608ed5206d6a67a791563c631cec07