Commit 7486341a authored by Li, Aubrey's avatar Li, Aubrey Committed by Ingo Molnar

x86/platform, acpi: Bypass legacy PIC and PIT in ACPI hardware reduced mode

On a platform in ACPI Hardware-reduced mode, the legacy PIC and
PIT may not be initialized even though they may be present in
silicon. Touching these legacy components causes unexpected
results on the system.

On the Bay Trail-T(ASUS-T100) platform, touching these legacy
components blocks platform hardware low idle power state(S0ix)
during system suspend. So we should bypass them in ACPI hardware
reduced mode.
Suggested-by: default avatarArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: default avatarLi Aubrey <aubrey.li@linux.intel.com>
Cc: <alan@linux.intel.com>
Cc: Alan Cox <alan@linux.intel.com>
Cc: H. Peter Anvin <hpa@linux.intel.com>
Cc: Len Brown <len.brown@intel.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Link: http://lkml.kernel.org/r/54FFF81C.20703@linux.intel.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 394838c9
...@@ -1337,6 +1337,26 @@ static int __init dmi_ignore_irq0_timer_override(const struct dmi_system_id *d) ...@@ -1337,6 +1337,26 @@ static int __init dmi_ignore_irq0_timer_override(const struct dmi_system_id *d)
return 0; return 0;
} }
/*
* ACPI offers an alternative platform interface model that removes
* ACPI hardware requirements for platforms that do not implement
* the PC Architecture.
*
* We initialize the Hardware-reduced ACPI model here:
*/
static void __init acpi_reduced_hw_init(void)
{
if (acpi_gbl_reduced_hardware) {
/*
* Override x86_init functions and bypass legacy pic
* in Hardware-reduced ACPI mode
*/
x86_init.timers.timer_init = x86_init_noop;
x86_init.irqs.pre_vector_init = x86_init_noop;
legacy_pic = &null_legacy_pic;
}
}
/* /*
* If your system is blacklisted here, but you find that acpi=force * If your system is blacklisted here, but you find that acpi=force
* works for you, please contact linux-acpi@vger.kernel.org * works for you, please contact linux-acpi@vger.kernel.org
...@@ -1536,6 +1556,11 @@ int __init early_acpi_boot_init(void) ...@@ -1536,6 +1556,11 @@ int __init early_acpi_boot_init(void)
*/ */
early_acpi_process_madt(); early_acpi_process_madt();
/*
* Hardware-reduced ACPI mode initialization:
*/
acpi_reduced_hw_init();
return 0; return 0;
} }
......
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