On 08/24/17 at 05:28pm, Dou Liyang wrote:
> Hi Baoquan,
>
> Thanks for your reply.
>
> At 08/24/2017 04:05 PM, Baoquan He wrote:
> > Hi Liyang,
> >
> > On 08/24/17 at 11:54am, Dou Liyang wrote:
> > > > > Test in my own PC(Lenovo M4340).
> > > > > Ask help for doing regression testing for the bug said in commit
> > > > > c4e1acbb35e4
> > > > > ("ACPI / init: Invoke early ACPI initialization later").
> > > > >
> > > >
> > > > Now, I can prove this patch doesn't result in the bug[1] which made the
> > > > fast TSC calibration using PIT failed in a Thinkpad x121e (AMD E-450
> > > > APU).
> > > >
> > > > The true reason of the bug is enabling ACPI subsystem earlier than
> > > > using PIT, not the SCI setup. invoking acpi_enable_subsystem() later
> >
> > Seems redhat mail server was down earlier, I didn't receive new mail in
> > this thread. Just curious, do you know why the fast tsc calibration
> > using PIT will fail if enabling ACPI subsystem earlier than using PIT?
> >
> It's related to particular hardware, As you know, I tested in many
> kinds of PC and laptop and PIT works well no matter before or after
> enabling ACPI subsystem.
>
> In pit_verify_msb(), we use inb(0x42) to read the current MSB,
>
> Normally, the value is continuously, like following shows:
>
> msb = fe
> msb = fd
> msb = fc
> msb = fb
> msb = fa
> msb = f9
> msb = f8
> msb = f7
> msb = f6
> ...
>
> But, if in some particular hardware, you will see like that:
>
> msb = fe
> msb = f0
> msb = ed
> msb = e9
> msb = e0
> msb = db
> ...
>
> In this case, the count in pit_expect_msb() is always zero.
> So we will see "Fast TSC calibration failed" in our dmesg log.
Thanks for telling!
It's truly weird that the TSC becomes unstable only if enabling ACPI
subsystem earlier than using PIT.
Let's see what other people say about this.
Btw, you will resend another round, right? Then I would like to test
your new post.
Thanks
Baoquan
>
> For the further deep reason why the hardware failed, I'm sorry
> I can't answer and don't know how to investigate. For hardware,
> I usually change a new one directly and know very little.
>
> Thanks,
> dou.
>
>
> > Thanks
> > Baoquan
> >
> > > > could fix this bug as Julian tested and said[2].
> > > >
> > > > And, I found that Commit b064a8fa77df (" ACPI / init: Switch over
> > > > platform to the ACPI mode later") split the ACPI early initialization
> > > > code into acpi_early_init() and acpi_subsystem_init(). executing
> > > > acpi_enable_subsystem() at the original early ACPI initialization spot.
> > > >
> > > > The sequence of them shows below:
> > > >
> > > > start_kernel
> > > > +---------------+
> > > > |
> > > > +--> .......
> > > > |
> > > > | late_time_init()
> > > > +--> +-------+
> > > > |
> > > > +--> .......
> > > > |
> > > > | acpi_early_init()
> > > > +--> +-------+
> > > > |
> > > > +--> .......
> > > > |
> > > > | acpi_subsystem_init()
> > > > +-> +--------+
> > > >
> > > > We make sure the acpi_subsystem_init() is called later than
> > > > late_time_init(), the bug will be avoided.
> > > >
> > > > This patch changes the sequence of late_time_init() and
> > > > acpi_early_init(), doesn't effect acpi_subsystem_init().
> > > >
> > > > So, this patch is OK.
> > > >
> > > > Btw, Thanks very much for Borislav Petkov, he will have access to
> > > > Thinkpad x121e from Mid-August and will test this series.
> > > >
> > >
> > > Almost one month passed, Borislav have tested this series in Thinkpad
> > > x121e and I also have tested in my box and QEmu again. It is OK.
> > >
> > > BTW,
> > > 1) I found your commit b064a8fa77df (" ACPI / init: Switch over
> > > platform to the ACPI mode later") split the ACPI early initialization
> > > code into acpi_early_init() and acpi_subsystem_init(). Actually enabling
> > > the ACPI subsystem is in acpi_subsystem_init().
> > >
> > > 2) As we discussed earlier, invoking acpi_put_table() is not good for
> > > this situation.
> > >
> > > So I do this patch, Is that goot to you? Any comments will be welcome.
> > >
> > > If it is OK, As the patches need to be re-based, and I also found
> > > several spelling mistake, I will send a new version next week.
> > >
> > > Thanks,
> > > dou.
> > >
> > > > [1] https://lkml.org/lkml/2014/3/10/123
> > > > [2] https://lkml.org/lkml/2014/3/12/311
> > > >
> > > >
> > > > Thanks
> > > > dou.
> > > >
> > > > > init/main.c | 2 +-
> > > > > 1 file changed, 1 insertion(+), 1 deletion(-)
> > > > >
> > > > > diff --git a/init/main.c b/init/main.c
> > > > > index df58a41..7a09467 100644
> > > > > --- a/init/main.c
> > > > > +++ b/init/main.c
> > > > > @@ -654,12 +654,12 @@ asmlinkage __visible void __init
> > > > > start_kernel(void)
> > > > > kmemleak_init();
> > > > > setup_per_cpu_pageset();
> > > > > numa_policy_init();
> > > > > + acpi_early_init();
> > > > > if (late_time_init)
> > > > > late_time_init();
> > > > > calibrate_delay();
> > > > > pidmap_init();
> > > > > anon_vma_init();
> > > > > - acpi_early_init();
> > > > > #ifdef CONFIG_X86
> > > > > if (efi_enabled(EFI_RUNTIME_SERVICES))
> > > > > efi_enter_virtual_mode();
> > > > >
> > >
> > >
> >
> >
> >
>
>
