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

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Message-ID: <0d8cc8c0-31a1-0290-5aa5-0c7b16db1edb@nvidia.com>
Date:   Wed, 16 Feb 2022 18:41:39 +0530
From:   Vidya Sagar <vidyas@...dia.com>
To:     "Kenneth R. Crudup" <kenny@...ix.com>,
        Bjorn Helgaas <helgaas@...nel.org>
CC:     <bhelgaas@...gle.com>, <lorenzo.pieralisi@....com>,
        <hkallweit1@...il.com>, <wangxiongfeng2@...wei.com>,
        <mika.westerberg@...ux.intel.com>, <kai.heng.feng@...onical.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>
Subject: Re: [PATCH V1] PCI/ASPM: Save/restore L1SS Capability for
 suspend/resume



On 2/16/2022 11:30 AM, Kenneth R. Crudup wrote:
> External email: Use caution opening links or attachments
> 
> 
> On Wed, 16 Feb 2022, Vidya Sagar wrote:
> 
>> I see that the ASPM-L1 state of Realtek NIC which was in disabled state before
>> hibernate got enabled after hibernate.
> 
> That's actually my SD-Card reader; there's a good chance the BIOS does "something"
> to it at boot time, as it's possible to boot from SD-Card on my laptop.
> 
>> This patch doesn't do anything to LnkCtl register which has control for ASPM L1
>> state.
> 
>> Could you please check why ASPM L1 got enabled post hibernation?
> 
> I wouldn't know how to do that; if you're still interested in that let me know
> what to do to determine that.
I would like Bjorn to take a call on it.
At this point, there are contradictions in observations.
Just to summarize,
- The root ports in your laptop don't have support for L1SS
- With the same old code base with which the errors were observed plus 
my patch on top of it, I see that ASPM-L1 state getting enabled for one 
of the endpoints (Realtek SD-Card reader) after system comes out of 
hibernation even though ASPM-L1 was disabled before the system enter 
into hibernation. No errors are reported now.
- With the linux-next top of the tree plus my patch, no change in the 
ASPM states and no errors also reported.

This points to BIOS being buggy (both old and new with new one being 
less problematic)

Bjorn, what are your comments on it?

> 
>          -Kenny
> 
> --
> Kenneth R. Crudup / Sr. SW Engineer, Scott County Consulting, Orange County CA
>