[MIPS] Rewrite all the assembler interrupt handlers to C.

Saves like 1,600 lines of code, is way easier to debug, compilers
frequently do a better job than the cut and paste type of handlers many
boards had.  And finally having all the stuff done in a single place
also means alot of bug potencial for the MT ASE is gone.

The only surviving handler in assembler is the DECstation one; I hope
Maciej will rewrite it.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 87 insertions, 4 deletions

diff --git a/arch/mips/mips-boards/malta/malta_int.c b/arch/mips/mips-boards/malta/malta_int.c
index d06dc5ad6c9e..1da8c18b9c8e 100644
--- a/arch/mips/mips-boards/malta/malta_int.c
+++ b/arch/mips/mips-boards/malta/malta_int.c
@@ -40,7 +40,6 @@
 #include <asm/mips-boards/msc01_pci.h>
 #include <asm/msc01_ic.h>
 
-extern asmlinkage void mipsIRQ(void);
 extern void mips_timer_interrupt(void);
 
 static DEFINE_SPINLOCK(mips_irq_lock);
@@ -114,7 +113,7 @@ static inline int get_int(void)
         return irq;
 }
 
-void malta_hw0_irqdispatch(struct pt_regs *regs)
+static void malta_hw0_irqdispatch(struct pt_regs *regs)
 {
         int irq;
 
@@ -182,6 +181,92 @@ void corehi_irqdispatch(struct pt_regs *regs)
         die("CoreHi interrupt", regs);
 }
 
+static inline int clz(unsigned long x)
+{
+        __asm__ (
+        "       .set    push                                    \n"
+        "       .set    mips32                                  \n"
+        "       clz     %0, %1                                  \n"
+        "       .set    pop                                     \n"
+        : "=r" (x)
+        : "r" (x));
+
+        return x;
+}
+
+/*
+ * Version of ffs that only looks at bits 12..15.
+ */
+static inline unsigned int irq_ffs(unsigned int pending)
+{
+#if defined(CONFIG_CPU_MIPS32) || defined(CONFIG_CPU_MIPS64)
+        return -clz(pending) + 31 - CAUSEB_IP;
+#else
+        unsigned int a0 = 7;
+        unsigned int t0;
+
+        t0 = s0 & 0xf000;
+        t0 = t0 < 1;
+        t0 = t0 << 2;
+        a0 = a0 - t0;
+        s0 = s0 << t0;
+
+        t0 = s0 & 0xc000;
+        t0 = t0 < 1;
+        t0 = t0 << 1;
+        a0 = a0 - t0;
+        s0 = s0 << t0;
+
+        t0 = s0 & 0x8000;
+        t0 = t0 < 1;
+        //t0 = t0 << 2;
+        a0 = a0 - t0;
+        //s0 = s0 << t0;
+
+        return a0;
+#endif
+}
+
+/*
+ * IRQs on the Malta board look basically (barring software IRQs which we
+ * don't use at all and all external interrupt sources are combined together
+ * on hardware interrupt 0 (MIPS IRQ 2)) like:
+ *
+ *      MIPS IRQ        Source
+ *      --------        ------
+ *             0        Software (ignored)
+ *             1        Software (ignored)
+ *             2        Combined hardware interrupt (hw0)
+ *             3        Hardware (ignored)
+ *             4        Hardware (ignored)
+ *             5        Hardware (ignored)
+ *             6        Hardware (ignored)
+ *             7        R4k timer (what we use)
+ *
+ * We handle the IRQ according to _our_ priority which is:
+ *
+ * Highest ----     R4k Timer
+ * Lowest  ----     Combined hardware interrupt
+ *
+ * then we just return, if multiple IRQs are pending then we will just take
+ * another exception, big deal.
+ */
+
+asmlinkage void plat_irq_dispatch(struct pt_regs *regs)
+{
+        unsigned int pending = read_c0_cause() & read_c0_status() & ST0_IM;
+        int irq;
+
+        irq = irq_ffs(pending);
+
+        if (irq == MIPSCPU_INT_I8259A)
+                malta_hw0_irqdispatch(regs);
+        else if (irq > 0)
+                do_IRQ(MIPSCPU_INT_BASE + irq, regs);
+        else
+                spurious_interrupt(regs);
+}
+
 static struct irqaction i8259irq = {
         .handler = no_action,
         .name = "XT-PIC cascade"
@@ -214,7 +299,6 @@ int __initdata msc_nr_eicirqs = sizeof(msc_eicirqmap)/sizeof(msc_irqmap_t);
 
 void __init arch_init_irq(void)
 {
-        set_except_vector(0, mipsIRQ);
         init_i8259_irqs();
 
         if (!cpu_has_veic)
@@ -245,7 +329,6 @@ void __init arch_init_irq(void)
                 setup_irq (MIPSCPU_INT_BASE+MIPSCPU_INT_COREHI, &corehi_irqaction);
         }
         else {
-                set_except_vector(0, mipsIRQ);
                 setup_irq (MIPSCPU_INT_BASE+MIPSCPU_INT_I8259A, &i8259irq);
                 setup_irq (MIPSCPU_INT_BASE+MIPSCPU_INT_COREHI, &corehi_irqaction);
         }