netdev - Re: [PATCH net 1/4] igc: Report speed and duplex as unknown when device is runtime suspended

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Message-ID: <107f90ab-0466-67e8-8cc5-7ac79513f939@intel.com>
Date:   Sat, 30 Jan 2021 16:00:06 +0200
From:   "Neftin, Sasha" <sasha.neftin@...el.com>
To:     Jakub Kicinski <kuba@...nel.org>,
        Tony Nguyen <anthony.l.nguyen@...el.com>
Cc:     davem@...emloft.net, Kai-Heng Feng <kai.heng.feng@...onical.com>,
        netdev@...r.kernel.org, sassmann@...hat.com,
        "Lifshits, Vitaly" <vitaly.lifshits@...el.com>,
        "Neftin, Sasha" <sasha.neftin@...el.com>
Subject: Re: [PATCH net 1/4] igc: Report speed and duplex as unknown when
 device is runtime suspended

On 1/30/2021 08:22, Jakub Kicinski wrote:
> On Thu, 28 Jan 2021 13:38:48 -0800 Tony Nguyen wrote:
>> From: Kai-Heng Feng <kai.heng.feng@...onical.com>
>>
>> Similar to commit 165ae7a8feb5 ("igb: Report speed and duplex as unknown
>> when device is runtime suspended"), if we try to read speed and duplex
>> sysfs while the device is runtime suspended, igc will complain and
>> stops working:
> 
>> The more generic approach will be wrap get_link_ksettings() with begin()
>> and complete() callbacks, and calls runtime resume and runtime suspend
>> routine respectively. However, igc is like igb, runtime resume routine
>> uses rtnl_lock() which upper ethtool layer also uses.
>>
>> So to prevent a deadlock on rtnl, take a different approach, use
>> pm_runtime_suspended() to avoid reading register while device is runtime
>> suspended.
> 
> Is someone working on the full fix to how PM operates?
> 
> There is another rd32(IGC_STATUS) in this file which I don't think
> is protected either.
Hello Jakub,
What is another rd32(IGC_STATUS) you meant? in  igc_ethtool_get_regs? 
While the device in D3 state there is no configuration space registers 
access.
sasha
>