Re: [Bug report] NVMe and RAID probe fail with commit cdf6b7362108

[Hanjun Guo <guohanjun@huawei.com>]

Hi Lukas,

Thank you for the quick reply.

On 2018/10/17 15:56, Lukas Wunner wrote:
> On Wed, Oct 17, 2018 at 11:38:11AM +0800, Hanjun Guo wrote:
>> We met NVMe and RAID probe failure on 4.19-rc1+ based kernel on
>> Hisilicon D06, then we bisect to this commit:
>>
>> cdf6b7362108 "PCI: pciehp: Always enable occupied slot on probe"
>>
>> Reverting this patch makes the system back to functional, I'm not
>> sure why this lead some regression on our board, could you share
>> some idea on this?
>>
>> Boot log below, [0] is the failure one, [1] is the good one,
>> please let me you if you need something more.
> 
> Please cherry-pick the following linux-next commit and test if the
> issue goes away:
> 
>     commit 80696f991424d05a784c0cf9c314ac09ac280406
>     Author: Lukas Wunner <lukas@wunner.de>
>     Date:   Sat Sep 8 09:59:01 2018 +0200
>     
>     PCI: pciehp: Tolerate Presence Detect hardwired to zero
> 
> If this does not fix the issue, please provide full dmesg output for
> the working and non-working case with "pciehp.pciehp_debug=1" on the
> kernel command line, preferrably attached to a bugzilla entry.
> 
> Detailed analysis of the dmesg output you've already provided:
> 
> There are 9 hotplug ports but devices are only present below 4 of them:
> a RAID adapter, a BMC with VGA, a 2x 10G Ethernet adapter and the NVMe drive:
> 
> 0000:00:00.0 [19e5:a120] bridge to [bus 01]
> 0000:00:04.0 [19e5:a120] bridge to [bus 02]
> 0000:00:08.0 [19e5:a120] bridge to [bus 03]: 0000:03:00.0 [1000:0097] mpt3sas *
> 0000:00:10.0 [19e5:a120] bridge to [bus 04]: 0000:04:00.0 [19e5:1711] hibmc   *
> 0000:00:12.0 [19e5:a120] bridge to [bus 05]: 0000:05:00.0 [8086:10fb] ixgbe
>                                              0000:05:00.1 [8086:10fb] ixgbe
> 0000:80:00.0 [19e5:a120] bridge to [bus 81]: 0000:81:00.0 [19e5:0123] nvme    *
> 0000:80:08.0 [19e5:a120] bridge to [bus 82]
> 0000:80:0c.0 [19e5:a120] bridge to [bus 83]
> 0000:80:10.0 [19e5:a120] bridge to [bus 84]
> 
> Of the 4 occupied hotplug ports, 3 exhibit a hardware bug wherein the link
> is reported to be up but the Presence Detect State bit in the Slot Status
> register is zero.  Consequently pciehp deems the slot unoccupied.
> I've marked the broken ports with an asterisk *.

Thank you very much for the clue, it helps a lot.

> 
> The above-mentioned commit works around such broken hardware but so far
> we knew only of a single affected chip, the Wilocity/QCA wil6210.
> It looks like this bug is more common than we thought, so it might be
> worth applying it already to v4.19.  However v4.19 is expected to be
> released in 4 days, so backporting to a 4.19 stable release might be
> more practical than squeezing the commit in before the coming Sunday.

Make sense to me.

> 
> For some reason the hotplug port 0000:00:12.0 with the 2x 10G Ethernet
> adapter does not exhibit the hardware bug.

After some debug of the hardware, only some ports were set to have the
capability for hotplug, 0000:00:12 is the one (obviously ports for nvme
and mpt3sas are not), so some behave OK and others are not, can be easily
fixed by BIOS and cpld logic on the board.

Thank you again for the help.
Hanjun