linux-kernel - Re: [PATCH v2] e1000e: Add a delay to let ME unconfigure s0ix when DPG_EXIT

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Date:   Fri, 29 Oct 2021 12:14:10 +0300
From:   Sasha Neftin <sasha.neftin@...el.com>
To:     Kai-Heng Feng <kai.heng.feng@...onical.com>
CC:     Jesse Brandeburg <jesse.brandeburg@...el.com>,
        "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>,
        AceLan Kao <acelan.kao@...onical.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "Dima Ruinskiy" <dima.ruinskiy@...el.com>,
        "moderated list:INTEL ETHERNET DRIVERS" 
        <intel-wired-lan@...ts.osuosl.org>,
        Linux Netdev List <netdev@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "Kraus, NechamaX" <nechamax.kraus@...ux.intel.com>,
        "Fuxbrumer, Devora" <devora.fuxbrumer@...el.com>,
        "Avivi, Amir" <amir.avivi@...el.com>,
        "Neftin, Sasha" <sasha.neftin@...el.com>
Subject: Re: [PATCH v2] e1000e: Add a delay to let ME unconfigure s0ix when
 DPG_EXIT_DONE is already flagged

On 10/27/2021 01:50, Kai-Heng Feng wrote:
> On Tue, Oct 26, 2021 at 4:48 PM Sasha Neftin <sasha.neftin@...el.com> wrote:
>>
>> On 10/26/2021 09:51, Kai-Heng Feng wrote:
>>> On some ADL platforms, DPG_EXIT_DONE is always flagged so e1000e resume
>>> polling logic doesn't wait until ME really unconfigures s0ix.
>>>
>>> So check DPG_EXIT_DONE before issuing EXIT_DPG, and if it's already
>>> flagged, wait for 1 second to let ME unconfigure s0ix.
>>>
>>> Fixes: 3e55d231716e ("e1000e: Add handshake with the CSME to support S0ix")
>>> Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=214821
>>> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
>>> ---
>>> v2:
>>>    Add missing "Fixes:" tag
>>>
>>>    drivers/net/ethernet/intel/e1000e/netdev.c | 7 +++++++
>>>    1 file changed, 7 insertions(+)
>>>
>>> diff --git a/drivers/net/ethernet/intel/e1000e/netdev.c b/drivers/net/ethernet/intel/e1000e/netdev.c
>>> index 44e2dc8328a22..cd81ba00a6bc9 100644
>>> --- a/drivers/net/ethernet/intel/e1000e/netdev.c
>>> +++ b/drivers/net/ethernet/intel/e1000e/netdev.c
>>> @@ -6493,14 +6493,21 @@ static void e1000e_s0ix_exit_flow(struct e1000_adapter *adapter)
>>>        u32 mac_data;
>>>        u16 phy_data;
>>>        u32 i = 0;
>>> +     bool dpg_exit_done;
>>>
>>>        if (er32(FWSM) & E1000_ICH_FWSM_FW_VALID) {
>>> +             dpg_exit_done = er32(EXFWSM) & E1000_EXFWSM_DPG_EXIT_DONE;
>>>                /* Request ME unconfigure the device from S0ix */
>>>                mac_data = er32(H2ME);
>>>                mac_data &= ~E1000_H2ME_START_DPG;
>>>                mac_data |= E1000_H2ME_EXIT_DPG;
>>>                ew32(H2ME, mac_data);
>>>
>>> +             if (dpg_exit_done) {
>>> +                     e_warn("DPG_EXIT_DONE is already flagged. This is a firmware bug\n");
>>> +                     msleep(1000);
>>> +             }
>> Thanks for working on the enablement.
>> The delay approach is fragile. We need to work with CSME folks to
>> understand why _DPG_EXIT_DONE indication is wrong on some ADL platforms.
>> Could you provide CSME/BIOS version? dmidecode -t 0 and cat
>> /sys/class/mei/mei0/fw_ver
> 
> $ sudo dmidecode -t 0
> # dmidecode 3.2
> Getting SMBIOS data from sysfs.
> SMBIOS 3.4 present.
> # SMBIOS implementations newer than version 3.2.0 are not
> # fully supported by this version of dmidecode.
> 
> Handle 0x0001, DMI type 0, 26 bytes
> BIOS Information
>          Vendor: Dell Inc.
>          Version: 0.12.68
>          Release Date: 10/01/2021
>          ROM Size: 48 MB
>          Characteristics:
>                  PCI is supported
>                  PNP is supported
>                  BIOS is upgradeable
>                  BIOS shadowing is allowed
>                  Boot from CD is supported
>                  Selectable boot is supported
>                  EDD is supported
>                  Print screen service is supported (int 5h)
>                  8042 keyboard services are supported (int 9h)
>                  Serial services are supported (int 14h)
>                  Printer services are supported (int 17h)
>                  ACPI is supported
>                  USB legacy is supported
>                  BIOS boot specification is supported
>                  Function key-initiated network boot is supported
>                  Targeted content distribution is supported
>                  UEFI is supported
>          BIOS Revision: 0.12
> 
> $ cat /sys/class/mei/mei0/fw_ver
> 0:16.0.15.1518
> 0:16.0.15.1518
> 0:16.0.15.1518
> 
Thank you Kai-Heng. The _DPG_EXIT_DONE bit indication comes from the 
EXFWSM register controlled by the CSME. We have only read access.  I 
realized that this indication was set to 1 even before our request to 
unconfigure the s0ix settings from the CSME. I am wondering. Does after 
a ~ 1s delay (or less, or more) _DPG_EXIT_DONE indication eventually 
change by CSME to 0? (is it consistently)
>>>                /* Poll up to 2.5 seconds for ME to unconfigure DPG.
>>>                 * If this takes more than 1 second, show a warning indicating a
>>>                 * firmware bug
>>>