1 files changed, 41 insertions, 16 deletions

diff --git a/arch/x86/kernel/i8259.c b/arch/x86/kernel/i8259.c
index 4d8aff05a509..f67063df6723 100644
--- a/arch/x86/kernel/i8259.c
+++ b/arch/x86/kernel/i8259.c
@@ -23,6 +23,7 @@
 #include <asm/desc.h>
 #include <asm/apic.h>
 #include <asm/i8259.h>
+#include <asm/io_apic.h>
 
 /*
  * This is the 'legacy' 8259A Programmable Interrupt Controller,
@@ -32,6 +33,7 @@
  */
 static void init_8259A(int auto_eoi);
 
+static bool pcat_compat __ro_after_init;
 static int i8259A_auto_eoi;
 DEFINE_RAW_SPINLOCK(i8259A_lock);
 
@@ -231,9 +233,7 @@ struct irq_chip i8259A_chip = {
 };
 
 static char irq_trigger[2];
-/**
- * ELCR registers (0x4d0, 0x4d1) control edge/level of IRQ
- */
+/* ELCR registers (0x4d0, 0x4d1) control edge/level of IRQ */
 static void restore_ELCR(char *trigger)
 {
 	outb(trigger[0], PIC_ELCR1);
@@ -247,19 +247,19 @@ static void save_ELCR(char *trigger)
 	trigger[1] = inb(PIC_ELCR2) & 0xDE;
 }
 
-static void i8259A_resume(void)
+static void i8259A_resume(void *data)
 {
 	init_8259A(i8259A_auto_eoi);
 	restore_ELCR(irq_trigger);
 }
 
-static int i8259A_suspend(void)
+static int i8259A_suspend(void *data)
 {
 	save_ELCR(irq_trigger);
 	return 0;
 }
 
-static void i8259A_shutdown(void)
+static void i8259A_shutdown(void *data)
 {
 	/* Put the i8259A into a quiescent state that
 	 * the kernel initialization code can get it
@@ -269,12 +269,16 @@ static void i8259A_shutdown(void)
 	outb(0xff, PIC_SLAVE_IMR);	/* mask all of 8259A-2 */
 }
 
-static struct syscore_ops i8259_syscore_ops = {
+static const struct syscore_ops i8259_syscore_ops = {
 	.suspend = i8259A_suspend,
 	.resume = i8259A_resume,
 	.shutdown = i8259A_shutdown,
 };
 
+static struct syscore i8259_syscore = {
+	.ops = &i8259_syscore_ops,
+};
+
 static void mask_8259A(void)
 {
 	unsigned long flags;
@@ -301,15 +305,32 @@ static void unmask_8259A(void)
 
 static int probe_8259A(void)
 {
+	unsigned char new_val, probe_val = ~(1 << PIC_CASCADE_IR);
 	unsigned long flags;
-	unsigned char probe_val = ~(1 << PIC_CASCADE_IR);
-	unsigned char new_val;
+
 	/*
-	 * Check to see if we have a PIC.
-	 * Mask all except the cascade and read
-	 * back the value we just wrote. If we don't
-	 * have a PIC, we will read 0xff as opposed to the
-	 * value we wrote.
+	 * If MADT has the PCAT_COMPAT flag set, then do not bother probing
+	 * for the PIC. Some BIOSes leave the PIC uninitialized and probing
+	 * fails.
+	 *
+	 * Right now this causes problems as quite some code depends on
+	 * nr_legacy_irqs() > 0 or has_legacy_pic() == true. This is silly
+	 * when the system has an IO/APIC because then PIC is not required
+	 * at all, except for really old machines where the timer interrupt
+	 * must be routed through the PIC. So just pretend that the PIC is
+	 * there and let legacy_pic->init() initialize it for nothing.
+	 *
+	 * Alternatively this could just try to initialize the PIC and
+	 * repeat the probe, but for cases where there is no PIC that's
+	 * just pointless.
+	 */
+	if (pcat_compat)
+		return nr_legacy_irqs();
+
+	/*
+	 * Check to see if we have a PIC.  Mask all except the cascade and
+	 * read back the value we just wrote. If we don't have a PIC, we
+	 * will read 0xff as opposed to the value we wrote.
 	 */
 	raw_spin_lock_irqsave(&i8259A_lock, flags);
 
@@ -427,9 +448,13 @@ EXPORT_SYMBOL(legacy_pic);
 static int __init i8259A_init_ops(void)
 {
 	if (legacy_pic == &default_legacy_pic)
-		register_syscore_ops(&i8259_syscore_ops);
+		register_syscore(&i8259_syscore);
 
 	return 0;
 }
-
 device_initcall(i8259A_init_ops);
+
+void __init legacy_pic_pcat_compat(void)
+{
+	pcat_compat = true;
+}