linux-kernel - Re: [Intel-wired-lan] Opportunistic S0ix blocked by e1000e when ethernet is in use

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Date:   Mon, 24 Jun 2019 14:56:58 +0300
From:   "Neftin, Sasha" <sasha.neftin@...el.com>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>,
        jeffrey.t.kirsher@...el.com
Cc:     intel-wired-lan@...ts.osuosl.org,
        Anthony Wong <anthony.wong@...onical.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [Intel-wired-lan] Opportunistic S0ix blocked by e1000e when
 ethernet is in use

On 6/24/2019 10:03, Kai-Heng Feng wrote:
> Hi Jeffrey,
> 
> at 19:08, Kai-Heng Feng <kai.heng.feng@...onical.com> wrote:
> 
>> Hi Jeffrey,
>>
>> There are several platforms that uses e1000e can’t enter Opportunistic 
>> S0ix (PC10) when the ethernet has a link partner.
>>
>> This behavior also exits in out-of-tree e1000e driver 3.4.2.1, but 
>> seems like 3.4.2.3 fixes the issue.
>>
>> A quick diff between the two versions shows that this code section may 
>> be our solution:
>>
>>         /* Read from EXTCNF_CTRL in e1000_acquire_swflag_ich8lan function
>>          * may occur during global reset and cause system hang.
>>          * Configuration space access creates the needed delay.
>>          * Write to E1000_STRAP RO register 
>> E1000_PCI_VENDOR_ID_REGISTER value
>>          * insures configuration space read is done before global reset.
>>          */
>>         pci_read_config_word(hw->adapter->pdev, 
>> E1000_PCI_VENDOR_ID_REGISTER,
>>                              &pci_cfg);
>>         ew32(STRAP, pci_cfg);
>>         e_dbg("Issuing a global reset to ich8lan\n");
>>         ew32(CTRL, (ctrl | E1000_CTRL_RST));
>>         /* cannot issue a flush here because it hangs the hardware */
>>         msleep(20);
>>
>>         /* Configuration space access improve HW level time sync 
>> mechanism.
>>          * Write to E1000_STRAP RO register E1000_PCI_VENDOR_ID_REGISTER
>>          * value to insure configuration space read is done
>>          * before any access to mac register.
>>          */
>>         pci_read_config_word(hw->adapter->pdev, 
>> E1000_PCI_VENDOR_ID_REGISTER,
>>                              &pci_cfg);
>>         ew32(STRAP, pci_cfg);
> 
> Turns out the "extra sauce” is not this part, it’s called “Dynamic LTR 
> support”.
> >>
>> Is there any plan to support this in the upstream kernel?
> 
> Is there any plan to support Dynamic LTR in upstream e1000e?
> 
Dynamic LTR is not stable solution. So, we can not put this solution to 
upstream. I hope we will be able to fix this in HW for a future projects.
S0ix support is under discussion with our architecture. We will try 
enable S0ix in our e1000e OOT driver as first step.
> Kai-Heng
> 
>>
>> Kai-Heng
> 
> 
> _______________________________________________
> Intel-wired-lan mailing list
> Intel-wired-lan@...osl.org
> https://lists.osuosl.org/mailman/listinfo/intel-wired-lan

Thanks
Sasha

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