[tip:x86/timers] x86/time: Unconditionally register legacy timer interrupt

[tip-bot for Peter Zijlstra]

Commit-ID:  6d671e1b85c63e7a337ba76c1a154c091545cff8
Gitweb:     https://git.kernel.org/tip/6d671e1b85c63e7a337ba76c1a154c091545cff8
Author:     Peter Zijlstra <peterz@xxxxxxxxxxxxx>
AuthorDate: Fri, 22 Dec 2017 10:20:12 +0100
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Sun, 14 Jan 2018 20:18:23 +0100

x86/time: Unconditionally register legacy timer interrupt

Even without a PIC/PIT the legacy timer interrupt is required for HPET in
legacy replacement mode.

Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: len.brown@xxxxxxxxx
Cc: rui.zhang@xxxxxxxxx
Link: https://lkml.kernel.org/r/20171222092243.382623763@xxxxxxxxxxxxx

---
 arch/x86/kernel/time.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/time.c b/arch/x86/kernel/time.c
index 749d189..774ebaf 100644
--- a/arch/x86/kernel/time.c
+++ b/arch/x86/kernel/time.c
@@ -69,9 +69,12 @@ static struct irqaction irq0  = {
 
 static void __init setup_default_timer_irq(void)
 {
-	if (!nr_legacy_irqs())
-		return;
-	setup_irq(0, &irq0);
+	/*
+	 * Unconditionally register the legacy timer; even without legacy
+	 * PIC/PIT we need this for the HPET0 in legacy replacement mode.
+	 */
+	if (setup_irq(0, &irq0))
+		pr_info("Failed to register legacy timer interrupt\n");
 }
 
 /* Default timer init function */