linux-kernel - Re: [BUG] Intel Apollolake: PCIe bridge "loses" capabilities after entering D3Cold state

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Message-ID: <20221021111935.GB28729@wunner.de>
Date:   Fri, 21 Oct 2022 13:19:35 +0200
From:   Lukas Wunner <lukas@...ner.de>
To:     Lukasz Majczak <lma@...ihalf.com>
Cc:     bhelgaas@...gle.com, Rajat Jain <rajatja@...gle.com>,
        Vidya Sagar <vidyas@...dia.com>, upstream@...ihalf.com,
        linux-pci@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] Intel Apollolake: PCIe bridge "loses" capabilities after
 entering D3Cold state

On Fri, Oct 21, 2022 at 12:17:35PM +0200, Lukasz Majczak wrote:
> While working with Vidya???s patch I have noticed that after
> suspend/resume cycle on my Chromebook (Apollolake) PCIe bridge loses
> its capabilities - the missing part is:
> 
> Capabilities: [200 v1] L1 PM Substates
> L1SubCap: PCI-PM_L1.2+ PCI-PM_L1.1+ ASPM_L1.2+ ASPM_L1.1+ L1_PM_Substates+
>   PortCommonModeRestoreTime=40us PortTPowerOnTime=10us
> L1SubCtl1: PCI-PM_L1.2+ PCI-PM_L1.1+ ASPM_L1.2+ ASPM_L1.1+
>    T_CommonMode=40us LTR1.2_Threshold=98304ns
> L1SubCtl2: T_PwrOn=60us
> 
> Digging more I???ve found out that entering D3Cold state causes this

You mean the capability is gone from lspci after D3cold?

My understanding is that BIOS is responsible for populating config space.
So this sounds like a BIOS bug.  What's the BIOS vendor and version?
(dmesg | grep DMI)

Thanks,

Lukas