MIPS: MT: proc: Add support for printing VPE and TC ids

And there are more CPUs or configurations that want to provide special
per-CPU information in /proc/cpuinfo.  So I think there needs to be a
hook mechanism, such as a notifier.

This is a first cut only; I need to think about what sort of looking
the notifier needs to have.  But I'd appreciate testing on MT hardware!
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Cc: Markos Chandras <markos.chandras@imgtec.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/6066/

arch/mips/include/asm/cpu-info.h

@@ -96,6 +96,27 @@ extern void cpu_report(void);
 extern const char *__cpu_name[];
 #define cpu_name_string()	__cpu_name[smp_processor_id()]
 
+struct seq_file;
+struct notifier_block;
+
+extern int register_proc_cpuinfo_notifier(struct notifier_block *nb);
+extern int proc_cpuinfo_notifier_call_chain(unsigned long val, void *v);
+
+#define proc_cpuinfo_notifier(fn, pri)					\
+({									\
+	static struct notifier_block fn##_nb = {			\
+		.notifier_call = fn,					\
+		.priority = pri						\
+	};								\
+									\
+	register_proc_cpuinfo_notifier(&fn##_nb);			\
+})
+
+struct proc_cpuinfo_notifier_args {
+	struct seq_file *m;
+	unsigned long n;
+};
+
 #if defined(CONFIG_MIPS_MT_SMP) || defined(CONFIG_MIPS_MT_SMTC)
 # define cpu_vpe_id(cpuinfo)	((cpuinfo)->vpe_id)
 #else

arch/mips/kernel/proc.c

@@ -17,8 +17,24 @@
 
 unsigned int vced_count, vcei_count;
 
+/*
+ *  * No lock; only written during early bootup by CPU 0.
+ *   */
+static RAW_NOTIFIER_HEAD(proc_cpuinfo_chain);
+
+int __ref register_proc_cpuinfo_notifier(struct notifier_block *nb)
+{
+	return raw_notifier_chain_register(&proc_cpuinfo_chain, nb);
+}
+
+int proc_cpuinfo_notifier_call_chain(unsigned long val, void *v)
+{
+	return raw_notifier_call_chain(&proc_cpuinfo_chain, val, v);
+}
+
 static int show_cpuinfo(struct seq_file *m, void *v)
 {
+	struct proc_cpuinfo_notifier_args proc_cpuinfo_notifier_args;
 	unsigned long n = (unsigned long) v - 1;
 	unsigned int version = cpu_data[n].processor_id;
 	unsigned int fp_vers = cpu_data[n].fpu_id;
@@ -120,6 +136,13 @@ static int show_cpuinfo(struct seq_file *m, void *v)
 		      cpu_has_vce ? "%u" : "not available");
 	seq_printf(m, fmt, 'D', vced_count);
 	seq_printf(m, fmt, 'I', vcei_count);
+
+	proc_cpuinfo_notifier_args.m = m;
+	proc_cpuinfo_notifier_args.n = n;
+
+	raw_notifier_call_chain(&proc_cpuinfo_chain, 0,
+				&proc_cpuinfo_notifier_args);
+
 	seq_printf(m, "\n");
 
 	return 0;

arch/mips/kernel/smp-mt.c

@@ -313,3 +313,25 @@ struct plat_smp_ops vsmp_smp_ops = {
 	.smp_setup		= vsmp_smp_setup,
 	.prepare_cpus		= vsmp_prepare_cpus,
 };
+
+static int proc_cpuinfo_chain_call(struct notifier_block *nfb,
+	unsigned long action_unused, void *data)
+{
+	struct proc_cpuinfo_notifier_args *pcn = data;
+	struct seq_file *m = pcn->m;
+	unsigned long n = pcn->n;
+
+	if (!cpu_has_mipsmt)
+		return NOTIFY_OK;
+
+	seq_printf(m, "VPE\t\t\t: %d\n", cpu_data[n].vpe_id);
+
+	return NOTIFY_OK;
+}
+
+static int __init proc_cpuinfo_notifier_init(void)
+{
+	return proc_cpuinfo_notifier(proc_cpuinfo_chain_call, 0);
+}
+
+subsys_initcall(proc_cpuinfo_notifier_init);

arch/mips/kernel/smtc-proc.c

@@ -77,3 +77,26 @@ void init_smtc_stats(void)
 
 	proc_create("smtc", 0444, NULL, &smtc_proc_fops);
 }
+
+static int proc_cpuinfo_chain_call(struct notifier_block *nfb,
+	unsigned long action_unused, void *data)
+{
+	struct proc_cpuinfo_notifier_args *pcn = data;
+	struct seq_file *m = pcn->m;
+	unsigned long n = pcn->n;
+
+	if (!cpu_has_mipsmt)
+		return NOTIFY_OK;
+
+	seq_printf(m, "VPE\t\t\t: %d\n", cpu_data[n].vpe_id);
+	seq_printf(m, "TC\t\t\t: %d\n", cpu_data[n].tc_id);
+
+	return NOTIFY_OK;
+}
+
+static int __init proc_cpuinfo_notifier_init(void)
+{
+	return proc_cpuinfo_notifier(proc_cpuinfo_chain_call, 0);
+}
+
+subsys_initcall(proc_cpuinfo_notifier_init);