acpi timer reads all ones [Was: efirtc + atrtc at the same time]

[Konstantin Belousov]

On Tue, May 26, 2020 at 06:22:13PM +0300, Andriy Gapon wrote:
> On 25/05/2020 11:37, Andriy Gapon wrote:
> > Also, there is another issue related to atrtc.
> > When I have both drivers attached, and also when I have only atrtc attached
> > (efi.rt.disabled=1), system clock jumps 10 minutes forward after each suspend /
> > resume cycle (S0 -> S3 -> S0).  That does not happen for reboot and shutdown
> > cycles.  I haven't investigated this deeper, but it is a curious problem.
> 
> Actually, I was wrong.  The problem can also occur with efirtc alone.
> Also, sometimes there is a different problem where there are no callouts for a
> period of time on the order of minutes.  I tracked it to cc_lastscan being set
> to a value greater than the current uptime.  So, any scheduled callout gets
> scheduled at cc_lastscan and it is a while before the uptime catches up.
> 
> It seemed that both issues were connected and were a result of the uptime
> jumping forward by some minutes and then jumping back to a sane value.
> If something important happened during the weird period, like getting time of
> day from hardware or invoking a callout, it lead to the observed effects.
> 
> So, that gave me some ideas where to add debugging checks.
> What I determined is that ACPI timer (ACPI-fast) could produce a reading of all
> 1-s like happens when there is no hardware response.
> 
> I caught one such instance and got a stack trace for it (but no crash dump
> because devices had not resumed yet):
> tc_windup() at tc_windup+0x318/frame 0xfffffe00a7a19300
> tc_ticktock() at tc_ticktock+0x4b/frame 0xfffffe00a7a19320
> hardclock() at hardclock+0x107/frame 0xfffffe00a7a19360
> handleevents() at handleevents+0xb3/frame 0xfffffe00a7a193a0
> timercb() at timercb+0x196/frame 0xfffffe00a7a193f0
> lapic_handle_timer() at lapic_handle_timer+0x98/frame 0xfffffe00a7a19420
> Xtimerint() at Xtimerint+0xb1/frame 0xfffffe00a7a19420
> --- interrupt, rip = 0xffffffff80b34500, rsp = 0xfffffe00a7a194f8, rbp =
> 0xfffffe00a7a19540 ---
> acpi_pcib_write_config() at acpi_pcib_write_config/frame 0xfffffe00a7a19540
> pci_cfg_restore() at pci_cfg_restore+0x2cc/frame 0xfffffe00a7a195a0
> pci_resume_child() at pci_resume_child+0xee/frame 0xfffffe00a7a195e0
> pci_resume() at pci_resume+0x49/frame 0xfffffe00a7a19630
> bus_generic_resume_child() at bus_generic_resume_child+0x43/frame 0xfffffe00a7a19650
> bus_generic_resume() at bus_generic_resume+0x29/frame 0xfffffe00a7a19680
> bus_generic_resume_child() at bus_generic_resume_child+0x43/frame 0xfffffe00a7a196a0
> bus_generic_resume() at bus_generic_resume+0x29/frame 0xfffffe00a7a196d0
> bus_generic_resume_child() at bus_generic_resume_child+0x43/frame 0xfffffe00a7a196f0
> bus_generic_resume() at bus_generic_resume+0x29/frame 0xfffffe00a7a19720
> bus_generic_resume_child() at bus_generic_resume_child+0x43/frame 0xfffffe00a7a19740
> root_resume() at root_resume+0x29/frame 0xfffffe00a7a19770
> acpi_EnterSleepState() at acpi_EnterSleepState+0x73b/frame 0xfffffe00a7a197f0
> acpi_AckSleepState() at acpi_AckSleepState+0x144/frame 0xfffffe00a7a19820
> devfs_ioctl() at devfs_ioctl+0xcb/frame 0xfffffe00a7a19870
> vn_ioctl() at vn_ioctl+0x132/frame 0xfffffe00a7a19980
> devfs_ioctl_f() at devfs_ioctl_f+0x1e/frame 0xfffffe00a7a199a0
> kern_ioctl() at kern_ioctl+0x27b/frame 0xfffffe00a7a19a00
> sys_ioctl() at sys_ioctl+0x123/frame 0xfffffe00a7a19ad0
> amd64_syscall() at amd64_syscall+0x140/frame 0xfffffe00a7a19bf0
> fast_syscall_common() at fast_syscall_common+0x101/frame 0xfffffe00a7a19bf0
> 
> I am not sure if this is just a coincidence but it appears as if a write to some
> PCI configuration register could temporarily interfere with access to the PM
> timer I/O port.
> Is that plausible?
If something disabled a BAR, then typical response of x86 chipset for timed
out read from PCIe is 0xfffff... .