linux-kernel - Re: [PATCH 0/3] PCI/ASPM: Fix L1SS issues

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Date:   Wed, 5 Oct 2022 12:57:44 -0500
From:   Bjorn Helgaas <helgaas@...nel.org>
To:     Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
Cc:     linux-pci@...r.kernel.org, Vidya Sagar <vidyas@...dia.com>,
        "Saheed O . Bolarinwa" <refactormyself@...il.com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Rajat Jain <rajatja@...gle.com>,
        "Kenneth R . Crudup" <kenny@...ix.com>,
        Kai-Heng Feng <kai.heng.feng@...onical.com>,
        Abhishek Sahu <abhsahu@...dia.com>,
        Thierry Reding <treding@...dia.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Krishna Thota <kthota@...dia.com>,
        Manikanta Maddireddy <mmaddireddy@...dia.com>,
        Vidya Sagar <sagar.tv@...il.com>, sagupta@...dia.com,
        linux-kernel@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>
Subject: Re: [PATCH 0/3] PCI/ASPM: Fix L1SS issues

On Tue, Oct 04, 2022 at 08:28:07PM -0700, Sathyanarayanan Kuppuswamy wrote:
> On 10/4/22 7:58 PM, Bjorn Helgaas wrote:
> > From: Bjorn Helgaas <bhelgaas@...gle.com>
> > 
> > This is really late, but I think we have two significant issues with L1SS:
> > 
> >   1) pcie_aspm_cap_init() reads from the L1SS capability even when it
> >   doesn't exist, so it reads PCI_COMMAND and PCI_STATUS instead and treats
> >   those as an L1SS Capability value.
> > 
> >   2) encode_l12_threshold() encodes LTR_L1.2_THRESHOLD as smaller than
> >   requested, so ports may enter L1.2 when they should not.
> > 
> > These patches are intended to fix both issues.
> 
> Looks good to me.
> 
> Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>

Thanks a lot for taking a look at these!  I put them on pci/aspm for
v6.1.

> > Bjorn Helgaas (3):
> >   PCI/ASPM: Factor out L1 PM Substates configuration
> >   PCI/ASPM: Ignore L1 PM Substates if device lacks capability
> >   PCI/ASPM: Correct LTR_L1.2_THRESHOLD computation
> > 
> >  drivers/pci/pcie/aspm.c | 155 +++++++++++++++++++++++-----------------
> >  1 file changed, 90 insertions(+), 65 deletions(-)
> > 
> 
> -- 
> Sathyanarayanan Kuppuswamy
> Linux Kernel Developer