From 7486341a98f26857f383aec88ffa10950087c3a1 Mon Sep 17 00:00:00 2001 From: "Li, Aubrey" Date: Wed, 11 Mar 2015 16:09:00 +0800 Subject: [PATCH] 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: Arjan van de Ven Signed-off-by: Li Aubrey Cc: Cc: Alan Cox Cc: H. Peter Anvin Cc: Len Brown Cc: Rafael J. Wysocki Cc: Rafael J. Wysocki Link: http://lkml.kernel.org/r/54FFF81C.20703@linux.intel.com Signed-off-by: Ingo Molnar --- arch/x86/kernel/acpi/boot.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c index 3d525c6..803b684 100644 --- a/arch/x86/kernel/acpi/boot.c +++ b/arch/x86/kernel/acpi/boot.c @@ -1338,6 +1338,26 @@ static int __init dmi_ignore_irq0_timer_override(const struct dmi_system_id *d) } /* + * 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 * works for you, please contact linux-acpi@vger.kernel.org */ @@ -1536,6 +1556,11 @@ int __init early_acpi_boot_init(void) */ early_acpi_process_madt(); + /* + * Hardware-reduced ACPI mode initialization: + */ + acpi_reduced_hw_init(); + return 0; } -- 2.7.4