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 23:06:44 +0800
From:   Kai-Heng Feng <kai.heng.feng@...onical.com>
To:     "Neftin, Sasha" <sasha.neftin@...el.com>
Cc:     jeffrey.t.kirsher@...el.com, 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

at 19:56, Neftin, Sasha <sasha.neftin@...el.com> wrote:

> 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.

Does this mean current generation hardware won’t get the fix?

> S0ix support is under discussion with our architecture. We will try  
> enable S0ix in our e1000e OOT driver as first step.

Is it possible to add Dynamic LTR as an option so users and downstream  
distros can still benefit from it?

Kai-Heng

>> 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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