MIPS: Add SysRq operation to dump TLBs on all CPUs

Add a MIPS specific SysRq operation to dump the TLB entries on all CPUs,
using the 'x' trigger key.
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/10072/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/kernel/Makefile

@@ -77,6 +77,7 @@ obj-$(CONFIG_MIPS32_O32)	+= binfmt_elfo32.o scall64-o32.o
 
 obj-$(CONFIG_KGDB)		+= kgdb.o
 obj-$(CONFIG_PROC_FS)		+= proc.o
+obj-$(CONFIG_MAGIC_SYSRQ)	+= sysrq.o
 
 obj-$(CONFIG_64BIT)		+= cpu-bugs64.o
 

arch/mips/kernel/sysrq.c

+/*
+ * MIPS specific sysrq operations.
+ *
+ * Copyright (C) 2015 Imagination Technologies Ltd.
+ */
+#include <linux/init.h>
+#include <linux/smp.h>
+#include <linux/spinlock.h>
+#include <linux/sysrq.h>
+#include <linux/workqueue.h>
+
+#include <asm/cpu-features.h>
+#include <asm/mipsregs.h>
+#include <asm/tlbdebug.h>
+
+/*
+ * Dump TLB entries on all CPUs.
+ */
+
+static DEFINE_SPINLOCK(show_lock);
+
+static void sysrq_tlbdump_single(void *dummy)
+{
+	const int field = 2 * sizeof(unsigned long);
+	unsigned long flags;
+
+	spin_lock_irqsave(&show_lock, flags);
+
+	pr_info("CPU%d:\n", smp_processor_id());
+	pr_info("Index	: %0x\n", read_c0_index());
+	pr_info("Pagemask: %0x\n", read_c0_pagemask());
+	pr_info("EntryHi : %0*lx\n", field, read_c0_entryhi());
+	pr_info("EntryLo0: %0*lx\n", field, read_c0_entrylo0());
+	pr_info("EntryLo1: %0*lx\n", field, read_c0_entrylo1());
+	pr_info("Wired   : %0x\n", read_c0_wired());
+	pr_info("Pagegrain: %0x\n", read_c0_pagegrain());
+	if (cpu_has_htw) {
+		pr_info("PWField : %0*lx\n", field, read_c0_pwfield());
+		pr_info("PWSize  : %0*lx\n", field, read_c0_pwsize());
+		pr_info("PWCtl   : %0x\n", read_c0_pwctl());
+	}
+	pr_info("\n");
+	dump_tlb_all();
+	pr_info("\n");
+
+	spin_unlock_irqrestore(&show_lock, flags);
+}
+
+#ifdef CONFIG_SMP
+static void sysrq_tlbdump_othercpus(struct work_struct *dummy)
+{
+	smp_call_function(sysrq_tlbdump_single, NULL, 0);
+}
+
+static DECLARE_WORK(sysrq_tlbdump, sysrq_tlbdump_othercpus);
+#endif
+
+static void sysrq_handle_tlbdump(int key)
+{
+	sysrq_tlbdump_single(NULL);
+#ifdef CONFIG_SMP
+	schedule_work(&sysrq_tlbdump);
+#endif
+}
+
+static struct sysrq_key_op sysrq_tlbdump_op = {
+	.handler        = sysrq_handle_tlbdump,
+	.help_msg       = "show-tlbs(x)",
+	.action_msg     = "Show TLB entries",
+	.enable_mask	= SYSRQ_ENABLE_DUMP,
+};
+
+static int __init mips_sysrq_init(void)
+{
+	return register_sysrq_key('x', &sysrq_tlbdump_op);
+}
+arch_initcall(mips_sysrq_init);

drivers/tty/sysrq.c

@@ -463,6 +463,7 @@ static struct sysrq_key_op *sysrq_key_table[36] = {
 	/* v: May be registered for frame buffer console restore */
 	NULL,				/* v */
 	&sysrq_showstate_blocked_op,	/* w */
+	/* x: May be registered on mips for TLB dump */
 	/* x: May be registered on ppc/powerpc for xmon */
 	/* x: May be registered on sparc64 for global PMU dump */
 	NULL,				/* x */