LoongArch: Remove the deprecated notifier hook mechanism

The notifier hook mechanism in proc and cpuinfo is actually unnecessary
for LoongArch because it's not used anywhere.

It was originally added to the MIPS code in commit d6d3c9a ("MIPS:
MT: proc: Add support for printing VPE and TC ids"), and LoongArch then
inherited it.

But as the kernel code stands now, this notifier hook mechanism doesn't
really make sense for either LoongArch or MIPS.

In addition, the seq_file forward declaration needs to be moved to its
proper place, as only the show_ipi_list() function in smp.c requires it.

Co-developed-by: Wentao Guan <[email protected]>
Signed-off-by: Wentao Guan <[email protected]>
Signed-off-by: Yuli Wang <[email protected]>
Signed-off-by: Huacai Chen <[email protected]>

Author: Avenger-285714

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

@@ -76,27 +76,6 @@ extern const char *__cpu_full_name[];
 #define cpu_family_string()	__cpu_family[raw_smp_processor_id()]
 #define cpu_full_name_string()	__cpu_full_name[raw_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;
-};
-
 static inline bool cpus_are_siblings(int cpua, int cpub)
 {
 	struct cpuinfo_loongarch *infoa = &cpu_data[cpua];

arch/loongarch/include/asm/smp.h

@@ -77,6 +77,8 @@ extern int __cpu_logical_map[NR_CPUS];
 #define SMP_IRQ_WORK		BIT(ACTION_IRQ_WORK)
 #define SMP_CLEAR_VECTOR	BIT(ACTION_CLEAR_VECTOR)
 
+struct seq_file;
+
 struct secondary_data {
 	unsigned long stack;
 	unsigned long thread_info;

arch/loongarch/kernel/proc.c

@@ -13,28 +13,12 @@
 #include <asm/processor.h>
 #include <asm/time.h>
 
-/*
- * 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)
 {
 	unsigned long n = (unsigned long) v - 1;
 	unsigned int isa = cpu_data[n].isa_level;
 	unsigned int version = cpu_data[n].processor_id & 0xff;
 	unsigned int fp_version = cpu_data[n].fpu_vers;
-	struct proc_cpuinfo_notifier_args proc_cpuinfo_notifier_args;
 
 #ifdef CONFIG_SMP
 	if (!cpu_online(n))
@@ -97,12 +81,6 @@ static int show_cpuinfo(struct seq_file *m, void *v)
 		      cpu_data[n].watch_ireg_count, cpu_data[n].watch_dreg_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\n");
 
 	return 0;