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SubjectRe: [RESEND] Fast TSC calibration fails with v3.14-rc1 and later
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Hi Rafael, 

於 三,2014-03-12 於 14:30 +0100,Rafael J. Wysocki 提到:
> > But I wonder: Can we simply enable SCI later? In other words, can
> we
> > split acpi_early_init() so that the part before
> acpi_enable_subsystem()
> > is done before timekeeping_init() and the part including and after
> > is done right after anon_vma_init()? Would the TAD initialization
> work
> > then?
>
> Below is a patch implementing that idea. Julian, can you please test
> this one too?
>
> Rafael
>
> ---
> drivers/acpi/bus.c | 20 +++++++++++++++-----
> include/linux/acpi.h | 1 +
> init/main.c | 1 +
> 3 files changed, 17 insertions(+), 5 deletions(-)
>
> Index: linux-pm/drivers/acpi/bus.c
> ===================================================================
> --- linux-pm.orig/drivers/acpi/bus.c
> +++ linux-pm/drivers/acpi/bus.c
> @@ -494,11 +494,21 @@ void __init acpi_early_init(void)
> }
>
> status = acpi_load_tables();
> - if (ACPI_FAILURE(status)) {
> - printk(KERN_ERR PREFIX
> - "Unable to load the System Description Tables
> \n");
> - goto error0;
> - }
> + if (ACPI_SUCCESS(status))
> + return;
> +
> + printk(KERN_ERR PREFIX "Unable to load the System Description
> Tables\n");
> +
> + error0:
> + disable_acpi();
> +}
> +
> +void __init acpi_subsystem_init(void)
> +{
> + acpi_status status;
> +
> + if (acpi_disabled)
> + return;
>

After check the DSDT of target machine, I afraid the above patch is not
enough to use _GRT and _SRT because they need opregion support of
SystemMemory and SystemIO for trigger SMM to access RTC.

In my current semifinished patches, I add code to run the
acpi_ev_install_region_handlers() in acpi_enable_subsystem() when
acpi_early_init(), for install region handler to support opregion.

Before install region_handlers, it call acpi_enable() to enable acpi
mode and I think need setup SCI interrupt before run acpi_enable():

acpi_early_init(void)
acpi_pic_sci_set_trigger(acpi_gbl_FADT.sci_interrupt,
acpi_enable_subsystem(u32 flags)
acpi_enable(); /* Enable ACPI mode */
acpi_tb_initialize_facs();
acpi_ev_install_region_handlers(); /* Need it! */


For developing ACPI TAD support, I used SystemIO to access CMOS port in
DSDT of Intel DQ57 for simulate ACPI TAD. It also need SystemIO opregion
support as the real machine. I just run your patch on this machine but
it failed.

I think maybe still using ACPI_FADT_NO_CMOS_RTC to check does
acpi_early_init() need run before timekeeping_init().
If there have any future machine that applied ACPI TAD but "Fast TSC
calibration" fail, at least the alternate TSC calibration can work
around issue.


Thanks a lot!
Joey Lee

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