linux-kernel - Re: [RFC 0/2] PCI/ASPM: Allow controller-defined default link state

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Message-ID: <gulatdqqxkdc4oafmqoqiyf2f6gzlk2nfxhy3l5yxx4oyxgppf@mhsmuq4xansa>
Date: Thu, 17 Jul 2025 07:03:42 -0700
From: David Box <david.e.box@...ux.intel.com>
To: Manivannan Sadhasivam <mani@...nel.org>
Cc: "Kenneth R. Crudup" <kenny@...ix.com>, rafael@...nel.org, 
	bhelgaas@...gle.com, vicamo.yang@...onical.com, ilpo.jarvinen@...ux.intel.com, 
	nirmal.patel@...ux.intel.com, linux-pm@...r.kernel.org, linux-pci@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [RFC 0/2] PCI/ASPM: Allow controller-defined default link state

On Thu, Jul 17, 2025 at 12:27:47PM +0530, Manivannan Sadhasivam wrote:
> On Wed, Jul 16, 2025 at 11:12:45PM GMT, Kenneth R. Crudup wrote:
> > 
> > Unfortunately, having tested the patch (against Linus' master), it doesn't work.
> > 
> > I don't think the ASPM(?) state is making it to the VMD.
> > 
> 
> Because, the VMD driver is not at all setting the PCI_BUS_FLAGS_NO_ASPM_DEFAULT
> flag.

Correct. I forgot to set the flag in the VMD driver. Other this approach
should have worked.

David

> But I proposed an alternate method [1] to enable ASPM which would avoid
> using the flag.
> 
> - Mani
> 
> [1] https://lore.kernel.org/linux-pci/4xcwba3d4slmz5gfuwypavxqreobnigzyu4vib6powtbibytyp@mmqcns27vlyr/
> 
> > LMK if you need more info.
> > 
> > -Kenny
> > 
> > On Wed, 16 Jul 2025, David E. Box wrote:
> > 
> > > Testing is appreciated as I didn't get a chance to do so yet but plan to.
> > 
> > > Thanks, David
> > >
> > > ---
> > >
> > > David E. Box (2):
> > >   PCI/ASPM: Allow drivers to provide ASPM link state via pci_bus
> > >   PCI: vmd: Provide default ASPM link state for synthetic hierarchy
> > >
> > >  drivers/pci/controller/vmd.c |  7 +++++--
> > >  drivers/pci/pcie/aspm.c      |  5 ++++-
> > >  include/linux/pci.h          | 12 ++++++++----
> > >  3 files changed, 17 insertions(+), 7 deletions(-)
> > >
> > >
> > > base-commit: d0b3b7b22dfa1f4b515fd3a295b3fd958f9e81af
> > >
> > 
> > -- 
> > Kenneth R. Crudup / Sr. SW Engineer, Scott County Consulting, Orange County CA
> > 
> 
> -- 
> மணிவண்ணன் சதாசிவம்