Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus

Pull MIPS fixes from Ralf Baechle:
 "Lantiq:
    - Fix adding xbar resoures causing a panic

  Loongson3:
    - Some Loongson 3A don't identify themselves as having an FTLB so
      hardwire that knowledge into CPU probing.
    - Handle Loongson 3 TLB peculiarities in the fast path of the RDHWR
      emulation.
    - Fix invalid FTLB entries with huge page on VTLB+FTLB platforms
    - Add missing calculation of S-cache and V-cache cache-way size

  Ralink:
    - Fix typos in rt3883 pinctrl data

  Generic:
    - Force o32 fp64 support on 32bit MIPS64r6 kernels
    - Yet another build fix after the linux/sched.h changes
    - Wire up statx system call
    - Fix stack unwinding after introduction of IRQ stack
    - Fix spinlock code to build even for microMIPS with recent binutils

  SMP-CPS:
    - Fix retrieval of VPE mask on big endian CPUs"

* 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus:
  MIPS: IRQ Stack: Unwind IRQ stack onto task stack
  MIPS: c-r4k: Fix Loongson-3's vcache/scache waysize calculation
  MIPS: Flush wrong invalid FTLB entry for huge page
  MIPS: Check TLB before handle_ri_rdhwr() for Loongson-3
  MIPS: Add MIPS_CPU_FTLB for Loongson-3A R2
  MIPS: Lantiq: fix missing xbar kernel panic
  MIPS: smp-cps: Fix retrieval of VPE mask on big endian CPUs
  MIPS: Wire up statx system call
  MIPS: Include asm/ptrace.h now linux/sched.h doesn't
  MIPS: ralink: Fix typos in rt3883 pinctrl
  MIPS: End spinlocks with .insn
  MIPS: Force o32 fp64 support on 32bit MIPS64r6 kernels

1 files changed, 15 insertions, 0 deletions

diff --git a/arch/mips/include/asm/irq.h b/arch/mips/include/asm/irq.h
index 956db6e201d1..ddd1c918103b 100644
--- a/arch/mips/include/asm/irq.h
+++ b/arch/mips/include/asm/irq.h
@@ -18,9 +18,24 @@
 #include <irq.h>
 
 #define IRQ_STACK_SIZE			THREAD_SIZE
+#define IRQ_STACK_START			(IRQ_STACK_SIZE - sizeof(unsigned long))
 
 extern void *irq_stack[NR_CPUS];
 
+/*
+ * The highest address on the IRQ stack contains a dummy frame put down in
+ * genex.S (handle_int & except_vec_vi_handler) which is structured as follows:
+ *
+ *   top ------------
+ *       | task sp  | <- irq_stack[cpu] + IRQ_STACK_START
+ *       ------------
+ *       |          | <- First frame of IRQ context
+ *       ------------
+ *
+ * task sp holds a copy of the task stack pointer where the struct pt_regs
+ * from exception entry can be found.
+ */
+
 static inline bool on_irq_stack(int cpu, unsigned long sp)
 {
 	unsigned long low = (unsigned long)irq_stack[cpu];