x86-64: clean up io-apic accesses

This is just commit 130fe05dbc0114609cfef9815c0c5580b42decfa ported to
x86-64, for all the same reasons.  It cleans up the IO-APIC accesses in
order to then fix the ordering issues.

We move the accessor functions (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, 46 insertions, 0 deletions

diff --git a/arch/x86_64/kernel/io_apic.c b/arch/x86_64/kernel/io_apic.c
index fe429e5d6b29..96e02d845716 100644
--- a/arch/x86_64/kernel/io_apic.c
+++ b/arch/x86_64/kernel/io_apic.c
@@ -88,6 +88,52 @@ static struct irq_pin_list {
         short 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.
+ */
+static inline void io_apic_modify(unsigned int apic, unsigned int value)
+{
+        struct io_apic __iomem *io_apic = io_apic_base(apic);
+        writel(value, &io_apic->data);
+}
+
+/*
+ * Synchronize the IO-APIC and the CPU by doing
+ * a dummy read from the IO-APIC
+ */
+static inline void io_apic_sync(unsigned int apic)
+{
+        struct io_apic __iomem *io_apic = io_apic_base(apic);
+        readl(&io_apic->data);
+}
+
 #define __DO_ACTION(R, ACTION, FINAL)                                   \
                                                                         \
 {                                                                       \