i386: clean up io-apic accesses

This is preparation for fixing the ordering of the accesses that
got broken by the commit cf4c6a2f27f5db810b69dcb1da7f194489e8ff88 when
factoring out the "common" io apic routing entry accesses.

Move the accessor function (that were only used by io_apic.c) out
of a header file, and use proper memory-mapped accesses rather than
making up our own "volatile" pointers.

Signed-off-by: Linus Torvalds <torvalds@osdl.org>

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;