Re: close() on some Intel CNP-LP PCI devices takes up to 2.7 s

[Paul Menzel]

Dear Mika,


Am 09.06.20 um 17:44 schrieb Mika Westerberg:
> On Tue, Jun 09, 2020 at 05:39:21PM +0200, Paul Menzel wrote:

> > On the Intel Cannon Point-LP laptop Dell Precision 3540 with a dedicated AMD
> > graphics card (both graphics devices can be used) with Debian Sid/unstable
> > with Linux 5.6.14, running lspci takes quite some time, and the screen even
> > flickers a short moment before the result is displayed.
> >
> > Tracing lspci with strace, shows that the close() function of the three
> > devices takes from
> >
> > â   00:1d.0 PCI bridge: Intel Corporation Cannon Point-LP PCI Express Root
> > Port #9
> >
> > â   04:00.0 System peripheral: Intel Corporation JHL6340 Thunderbolt 3 NHI
> > (C step) [Alpine Ridge 2C 2016] (rev 02)
> >
> > â   3b:00.0 Display controller: Advanced Micro Devices, Inc. [AMD/ATI] Lexa
> > XT [Radeon PRO WX 3100]
> >
> > takes from 270 ms to 2.5 s.
> >
> > > 11:43:21.714391 openat(AT_FDCWD, "/sys/bus/pci/devices/0000:04:00.0/config", O_RDONLY) = 3
> > > 11:43:21.714448 pread64(3, "\206\200\331\25\6\4\20\0\2\0\200\10 \0\0\0\0\0\0\352\0\0\4\352\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0(\20\272\10\0\0\0\0\
> > > 200\0\0\0\0\0\0\0\377\1\0\0", 64, 0) = 64
> > > 11:43:24.487818 close(3)                = 0
> >
> > > 11:43:24.489508 openat(AT_FDCWD, "/sys/bus/pci/devices/0000:00:1d.0/config", O_RDONLY) = 3
> > > 11:43:24.489598 pread64(3, "\206\200\260\235\7\4\20\0\360\0\4\6\20\0\201\0\0\0\0\0\0\0\0\0\0;;\00000\0  \354 \354\1\300\21\320\0\0\0\0\0\0\0\0\0\0\0\0
> > > @\0\0\0\0\0\0\0\377\1\22\0", 64, 0) = 64
> > > 11:43:24.966661 close(3)                = 0
> >
> > > 11:43:24.988544 openat(AT_FDCWD, "/sys/bus/pci/devices/0000:3b:00.0/config", O_RDONLY) = 3
> > > 11:43:24.988584 pread64(3, "\2\20\205i\7\4\20\0\0\0\200\3\20\0\0\0\f\0\0\300\0\0\0\0\f\0\0\320\0\0\0\0\0010\0\0\0\0 \354\0\0\0\0(\20\272\10\0\0$\354H\0\0\0\0\0\0\0\377\1\0\0", 64, 0) = 64
> > > 11:43:25.252745 close(3)
> >
> > Unfortunately, I forgot to collect the tree output, but hopefully the
> > attached Linux messages and strace of lspci output will be enough for the
> > start.
> >
> > Please tell me, if you want me to create a bug report in the Linux bug
> > tracker.
>
> Can you try this commit?
>
>    https://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci.git/commit/?h=pci/pm&id=ec411e02b7a2e785a4ed9ed283207cd14f48699d
>
> It should be in the mainline already as well.
>
> Note we still need to obey the delays required by the PCIe spec so 100ms
> after the link is trained but this one should at least get it down from
> 1100ms.

Thank you for replying so quickly. Hopefully, Iâll be able to test the 
commit tomorrow.

One question though. The commit talks about resuming from suspend. I 
understand that training happens there.

In my case the system is already running. So I wonder, why link(?) 
training would still happening.


Kind regards,

Paul