[MIPS] IRQ Affinity Support for SMTC on Malta Platform

    
Signed-off-by: Kevin D. Kissell <kevink@mips.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

2 files changed, 66 insertions, 2 deletions

diff --git a/include/asm-mips/irq.h b/include/asm-mips/irq.h
index 2cb52cf8bd4e..a58f0eecc68f 100644
--- a/include/asm-mips/irq.h
+++ b/include/asm-mips/irq.h
@@ -46,6 +46,38 @@ static inline void smtc_im_ack_irq(unsigned int irq)
 
 #endif /* CONFIG_MIPS_MT_SMTC */
 
+#ifdef CONFIG_MIPS_MT_SMTC_IRQAFF
+#include <linux/cpumask.h>
+
+extern void plat_set_irq_affinity(unsigned int irq, cpumask_t affinity);
+extern void smtc_forward_irq(unsigned int irq);
+
+/*
+ * IRQ affinity hook invoked at the beginning of interrupt dispatch
+ * if option is enabled.
+ *
+ * Up through Linux 2.6.22 (at least) cpumask operations are very
+ * inefficient on MIPS.  Initial prototypes of SMTC IRQ affinity
+ * used a "fast path" per-IRQ-descriptor cache of affinity information
+ * to reduce latency.  As there is a project afoot to optimize the
+ * cpumask implementations, this version is optimistically assuming
+ * that cpumask.h macro overhead is reasonable during interrupt dispatch.
+ */
+#define IRQ_AFFINITY_HOOK(irq)                                          \
+do {                                                                    \
+    if (!cpu_isset(smp_processor_id(), irq_desc[irq].affinity)) {       \
+        smtc_forward_irq(irq);                                          \
+        irq_exit();                                                     \
+        return;                                                         \
+    }                                                                   \
+} while (0)
+
+#else /* Not doing SMTC affinity */
+
+#define IRQ_AFFINITY_HOOK(irq) do { } while (0)
+
+#endif /* CONFIG_MIPS_MT_SMTC_IRQAFF */
+
 #ifdef CONFIG_MIPS_MT_SMTC_IM_BACKSTOP
 
 /*
@@ -56,13 +88,27 @@ static inline void smtc_im_ack_irq(unsigned int irq)
  */
 #define __DO_IRQ_SMTC_HOOK(irq)                                         \
 do {                                                                    \
+        IRQ_AFFINITY_HOOK(irq);                                         \
         if (irq_hwmask[irq] & 0x0000ff00)                               \
                 write_c0_tccontext(read_c0_tccontext() &                \
-                                   ~(irq_hwmask[irq] & 0x0000ff00));    \
+                                   ~(irq_hwmask[irq] & 0x0000ff00));    \
+} while (0)
+
+#define __NO_AFFINITY_IRQ_SMTC_HOOK(irq)                                \
+do {                                                                    \
+        if (irq_hwmask[irq] & 0x0000ff00)                               \
+                write_c0_tccontext(read_c0_tccontext() &                \
+                                   ~(irq_hwmask[irq] & 0x0000ff00));    \
 } while (0)
+
 #else
 
-#define __DO_IRQ_SMTC_HOOK(irq) do { } while (0)
+#define __DO_IRQ_SMTC_HOOK(irq)                                         \
+do {                                                                    \
+        IRQ_AFFINITY_HOOK(irq);                                         \
+} while (0)
+#define __NO_AFFINITY_IRQ_SMTC_HOOK(irq) do { } while (0)
+
 #endif
 
 /*
@@ -81,6 +127,23 @@ do {									\
         irq_exit();                                                     \
 } while (0)
 
+#ifdef CONFIG_MIPS_MT_SMTC_IRQAFF
+/*
+ * To avoid inefficient and in some cases pathological re-checking of
+ * IRQ affinity, we have this variant that skips the affinity check.
+ */
+
+
+#define do_IRQ_no_affinity(irq)                                         \
+do {                                                                    \
+        irq_enter();                                                    \
+        __NO_AFFINITY_IRQ_SMTC_HOOK(irq);                               \
+        generic_handle_irq(irq);                                        \
+        irq_exit();                                                     \
+} while (0)
+
+#endif /* CONFIG_MIPS_MT_SMTC_IRQAFF */
+
 extern void arch_init_irq(void);
 extern void spurious_interrupt(void);
 
diff --git a/include/asm-mips/smtc_ipi.h b/include/asm-mips/smtc_ipi.h
index a52a4a7a36e0..e09131a6127d 100644
--- a/include/asm-mips/smtc_ipi.h
+++ b/include/asm-mips/smtc_ipi.h
@@ -34,6 +34,7 @@ struct smtc_ipi {
 
 #define LINUX_SMP_IPI 1
 #define SMTC_CLOCK_TICK 2
+#define IRQ_AFFINITY_IPI 3
 
 /*
  * A queue of IPI messages