diff mbox

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

Message ID 1427139403-31938-1-git-send-email-colin.king@canonical.com
State New
Headers show

Commit Message

Colin Ian King March 23, 2015, 7:36 p.m. UTC 
From: "Li, Aubrey" <aubrey.li@linux.intel.com>

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 <arjan@linux.intel.com>
Signed-off-by: Li 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.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
(cherry picked from upstream commit 7486341a98f26857f383aec88ffa10950087c3a1)
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 arch/x86/kernel/acpi/boot.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

Comments

Seth Forshee March 23, 2015, 7:45 p.m. UTC | #1
Stefan Bader March 24, 2015, 8:21 a.m. UTC | #2 
Looks to be doing what is described in the comment and might be a need to have.
Looks to be testable with the right hw and contained by specific acpi mode.
Andy Whitcroft March 24, 2015, 8:40 a.m. UTC | #3 
Applied to vivid.

-apw
diff mbox

Patch

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;
 }