1 files changed, 40 insertions, 0 deletions

diff --git a/arch/i386/kernel/io_apic.c b/arch/i386/kernel/io_apic.c
index 350192d6ab98..eb10bd5da64e 100644
--- a/arch/i386/kernel/io_apic.c
+++ b/arch/i386/kernel/io_apic.c
@@ -91,6 +91,46 @@ static struct irq_pin_list {
         int apic, pin, next;
 } irq_2_pin[PIN_MAP_SIZE];
 
+struct io_apic {
+        unsigned int index;
+        unsigned int unused[3];
+        unsigned int data;
+};
+
+static __attribute_const__ struct io_apic __iomem *io_apic_base(int idx)
+{
+        return (void __iomem *) __fix_to_virt(FIX_IO_APIC_BASE_0 + idx)
+                + (mp_ioapics[idx].mpc_apicaddr & ~PAGE_MASK);
+}
+
+static inline unsigned int io_apic_read(unsigned int apic, unsigned int reg)
+{
+        struct io_apic __iomem *io_apic = io_apic_base(apic);
+        writel(reg, &io_apic->index);
+        return readl(&io_apic->data);
+}
+
+static inline void io_apic_write(unsigned int apic, unsigned int reg, unsigned int value)
+{
+        struct io_apic __iomem *io_apic = io_apic_base(apic);
+        writel(reg, &io_apic->index);
+        writel(value, &io_apic->data);
+}
+
+/*
+ * Re-write a value: to be used for read-modify-write
+ * cycles where the read already set up the index register.
+ *
+ * Older SiS APIC requires we rewrite the index register
+ */
+static inline void io_apic_modify(unsigned int apic, unsigned int reg, unsigned int value)
+{
+        volatile struct io_apic *io_apic = io_apic_base(apic);
+        if (sis_apic_bug)
+                writel(reg, &io_apic->index);
+        writel(value, &io_apic->data);
+}
+
 union entry_union {
         struct { u32 w1, w2; };
         struct IO_APIC_route_entry entry;