linux-kernel - Re: [PATCH V1] PCI/ASPM: Save/restore L1SS Capability for suspend/resume

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Message-ID: <CAAd53p6DX2C7KVRV=uu_mmPTTjE7=RsXfNPxjbOBLRbf-pXi5A@mail.gmail.com>
Date:   Fri, 15 Apr 2022 22:26:19 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     Bjorn Helgaas <helgaas@...nel.org>
Cc:     Vidya Sagar <vidyas@...dia.com>,
        "Kenneth R. Crudup" <kenny@...ix.com>, bhelgaas@...gle.com,
        lorenzo.pieralisi@....com, hkallweit1@...il.com,
        wangxiongfeng2@...wei.com, mika.westerberg@...ux.intel.com,
        chris.packham@...iedtelesis.co.nz, yangyicong@...ilicon.com,
        treding@...dia.com, jonathanh@...dia.com, abhsahu@...dia.com,
        sagupta@...dia.com, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, kthota@...dia.com,
        mmaddireddy@...dia.com, sagar.tv@...il.com,
        Ricky Wu <ricky_wu@...ltek.com>,
        Rajat Jain <rajatja@...gle.com>,
        Prasad Malisetty <quic_pmaliset@...cinc.com>,
        Victor Ding <victording@...gle.com>
Subject: Re: [PATCH V1] PCI/ASPM: Save/restore L1SS Capability for suspend/resume

On Fri, Apr 15, 2022 at 12:41 AM Bjorn Helgaas <helgaas@...nel.org> wrote:
>
> On Wed, Apr 13, 2022 at 08:19:26AM +0800, Kai-Heng Feng wrote:
> > On Wed, Apr 13, 2022 at 6:50 AM Bjorn Helgaas <helgaas@...nel.org> wrote:
> > > ...
>
> > >   - For L1 PM Substates configuration, sec 5.5.4 says that both ports
> > >     must be configured while ASPM L1 is disabled, but I don't think we
> > >     currently guarantee this: we restore all the upstream component
> > >     state first, and we don't know the ASPM state of the downstream
> > >     one.  Maybe we need to:
> > >
> > >       * When restoring upstream component,
> > >           + disable its ASPM
> > >
> > >       * When restoring downstream component,
> > >           + disable its ASPM
> > >           + restore upstream component's LTR, L1SS
> > >           + restore downstream component's LTR, L1SS
> > >           + restore upstream component's ASPM
> > >           + restore downstream component's ASPM
> >
> > Right now L1SS isn't reprogrammed after S3, and that causes WD NVMe
> > starts to spew lots of AER errors.
>
> Right now we don't fully restore L1SS-related state after S3, so maybe
> there's some inconsistency that leads to the AER errors.
>
> Could you collect the "lspci -vv" state before and after S3 so we can
> compare them?
>
> > So yes please restore L1SS upon resume. Meanwhile I am asking vendor
> > _why_ restoring L1SS is crucial for it to work.
> >
> > I also wonder what's the purpose of pcie_aspm_pm_state_change()? Can't
> > we just restore ASPM bits like other configs?
>
> Good question.  What's the context?  This is in the
> pci_raw_set_power_state() path, not the pci_restore_state() path, so
> seems like a separate discussion.

Because this patch alone doesn't restore T_PwrOn and LTR1.2_Threshold.

So I forced the pcie_aspm_pm_state_change() calling path to eventually
call aspm_calc_l1ss_info() which solved the problem for me.

Let me investigate a bit further.

Kai-Heng

>
> Bjorn