powerpc/rtas: remove lock and args fields from global rtas struct

Only code internal to the RTAS subsystem needs access to the central
lock and parameter block. Remove these from the globally visible
'rtas' struct and make them file-static in rtas.c.

Some changed lines in rtas_call() lack appropriate spacing around
operators and cause checkpatch errors; fix these as well.
Suggested-by: Laurent Dufour <ldufour@linux.ibm.com>
Signed-off-by: Nathan Lynch <nathanl@linux.ibm.com>
Reviewed-by: Laurent Dufour <laurent.dufour@fr.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20230124140448.45938-4-nathanl@linux.ibm.com

arch/powerpc/include/asm/rtas-types.h

@@ -18,8 +18,6 @@ struct rtas_t {
 	unsigned long entry;		/* physical address pointer */
 	unsigned long base;		/* physical address pointer */
 	unsigned long size;
-	arch_spinlock_t lock;
-	struct rtas_args args;
 	struct device_node *dev;	/* virtual address pointer */
 };
 

arch/powerpc/kernel/rtas.c

@@ -60,9 +60,17 @@ static inline void do_enter_rtas(unsigned long args)
 	srr_regs_clobbered(); /* rtas uses SRRs, invalidate */
 }
 
-struct rtas_t rtas = {
-	.lock = __ARCH_SPIN_LOCK_UNLOCKED
-};
+struct rtas_t rtas;
+
+/*
+ * Nearly all RTAS calls need to be serialized. All uses of the
+ * default rtas_args block must hold rtas_lock.
+ *
+ * Exceptions to the RTAS serialization requirement (e.g. stop-self)
+ * must use a separate rtas_args structure.
+ */
+static arch_spinlock_t rtas_lock = __ARCH_SPIN_LOCK_UNLOCKED;
+static struct rtas_args rtas_args;
 
 DEFINE_SPINLOCK(rtas_data_buf_lock);
 EXPORT_SYMBOL_GPL(rtas_data_buf_lock);
@@ -90,13 +98,13 @@ static unsigned long lock_rtas(void)
 
 	local_irq_save(flags);
 	preempt_disable();
-	arch_spin_lock(&rtas.lock);
+	arch_spin_lock(&rtas_lock);
 	return flags;
 }
 
 static void unlock_rtas(unsigned long flags)
 {
-	arch_spin_unlock(&rtas.lock);
+	arch_spin_unlock(&rtas_lock);
 	local_irq_restore(flags);
 	preempt_enable();
 }
@@ -114,7 +122,7 @@ static void call_rtas_display_status(unsigned char c)
 		return;
 
 	s = lock_rtas();
-	rtas_call_unlocked(&rtas.args, 10, 1, 1, NULL, c);
+	rtas_call_unlocked(&rtas_args, 10, 1, 1, NULL, c);
 	unlock_rtas(s);
 }
 
@@ -384,7 +392,7 @@ static int rtas_last_error_token;
  *  most recent failed call to rtas.  Because the error text
  *  might go stale if there are any other intervening rtas calls,
  *  this routine must be called atomically with whatever produced
- *  the error (i.e. with rtas.lock still held from the previous call).
+ *  the error (i.e. with rtas_lock still held from the previous call).
  */
 static char *__fetch_rtas_last_error(char *altbuf)
 {
@@ -404,13 +412,13 @@ static char *__fetch_rtas_last_error(char *altbuf)
 	err_args.args[1] = cpu_to_be32(bufsz);
 	err_args.args[2] = 0;
 
-	save_args = rtas.args;
-	rtas.args = err_args;
+	save_args = rtas_args;
+	rtas_args = err_args;
 
-	do_enter_rtas(__pa(&rtas.args));
+	do_enter_rtas(__pa(&rtas_args));
 
-	err_args = rtas.args;
-	rtas.args = save_args;
+	err_args = rtas_args;
+	rtas_args = save_args;
 
 	/* Log the error in the unlikely case that there was one. */
 	if (unlikely(err_args.args[2] == 0)) {
@@ -532,7 +540,7 @@ int rtas_call(int token, int nargs, int nret, int *outputs, ...)
 	va_list list;
 	int i;
 	unsigned long s;
-	struct rtas_args *rtas_args;
+	struct rtas_args *args;
 	char *buff_copy = NULL;
 	int ret;
 
@@ -557,21 +565,21 @@ int rtas_call(int token, int nargs, int nret, int *outputs, ...)
 	s = lock_rtas();
 
 	/* We use the global rtas args buffer */
-	rtas_args = &rtas.args;
+	args = &rtas_args;
 
 	va_start(list, outputs);
-	va_rtas_call_unlocked(rtas_args, token, nargs, nret, list);
+	va_rtas_call_unlocked(args, token, nargs, nret, list);
 	va_end(list);
 
 	/* A -1 return code indicates that the last command couldn't
 	   be completed due to a hardware error. */
-	if (be32_to_cpu(rtas_args->rets[0]) == -1)
+	if (be32_to_cpu(args->rets[0]) == -1)
 		buff_copy = __fetch_rtas_last_error(NULL);
 
 	if (nret > 1 && outputs != NULL)
 		for (i = 0; i < nret-1; ++i)
-			outputs[i] = be32_to_cpu(rtas_args->rets[i+1]);
-	ret = (nret > 0)? be32_to_cpu(rtas_args->rets[0]): 0;
+			outputs[i] = be32_to_cpu(args->rets[i + 1]);
+	ret = (nret > 0) ? be32_to_cpu(args->rets[0]) : 0;
 
 	unlock_rtas(s);
 
@@ -1265,9 +1273,9 @@ SYSCALL_DEFINE1(rtas, struct rtas_args __user *, uargs)
 
 	flags = lock_rtas();
 
-	rtas.args = args;
-	do_enter_rtas(__pa(&rtas.args));
-	args = rtas.args;
+	rtas_args = args;
+	do_enter_rtas(__pa(&rtas_args));
+	args = rtas_args;
 
 	/* A -1 return code indicates that the last command couldn't
 	   be completed due to a hardware error. */