git: 8254: Don't setup 8254 interrupt, if it is not selected as interrupt cputimer
sepherosa at gmail.com
Sat Mar 26 05:43:13 PDT 2011
On Sat, Mar 26, 2011 at 2:28 AM, Matthew Dillon
<dillon at apollo.backplane.com> wrote:
> : 8254: Don't setup 8254 interrupt, if it is not selected as interrupt cputimer
> : 8254 interrupt is setup, mainly to support C-state > C1, however, on some
> : systems it could cause system freezing during boot. Change the default value
> : of hw.i8254.intr_disable to 1, so more systems could boot by default.
> :Summary of changes:
> : sys/platform/pc32/isa/clock.c | 2 +-
> : sys/platform/pc64/isa/clock.c | 2 +-
> : 2 files changed, 2 insertions(+), 2 deletions(-)
> Hmm. Are we assuming that HPET or ACPI timers will always be available
> now? Any kernel loaded without ACPI won't see the ACPI timer (I think),
No, i8254 is always available as non-interrupt cputimer. User can't
change that, i.e. no tunable to prevent i8254 to become a usable
non-interrupt cputimer. It is not changed by this commit, so ACPI is
not a must.
> and maybe not the HPET either. The implication is that ACPI must always
> be loaded now.
> Maybe the real question is... if no other timers are available will the
> 8254 still be used to generate interrupts with this new default?
Yes, if i8254 is selected as interrupt cputimer (normally means lapic
is not available), hw.i8254.intr_disable will be ignored.
Tomorrow Will Never Die
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