Subject: [PATCH v2 3/4] powerpc/rtas: remove lock and args fields from global rtas struct

From: Nathan Lynch <[email-masked]>
Date: Tue, 24 Jan 2023 08:04:47 -0600

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 <[email-masked]>
Signed-off-by: Nathan Lynch <[email-masked]>
---
 arch/powerpc/include/asm/rtas-types.h |  2 --
 arch/powerpc/kernel/rtas.c            | 50 ++++++++++++++++-----------
 2 files changed, 29 insertions(+), 23 deletions(-)

diff --git a/arch/powerpc/include/asm/rtas-types.h b/arch/powerpc/include/asm/rtas-types.h
index 8df6235d64d1..f2ad4a96cbc5 100644
--- a/arch/powerpc/include/asm/rtas-types.h
+++ b/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 */
 };
 
diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
index e60e2f5af7b9..0059bb2a8f04 100644
--- a/arch/powerpc/kernel/rtas.c
+++ b/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);
 }
 
@@ -386,7 +394,7 @@ 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)
 {
@@ -406,13 +414,13 @@ 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)) {
@@ -534,7 +542,7 @@ 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;
 
@@ -559,21 +567,21 @@ 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);
 
@@ -1269,9 +1277,9 @@ 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. */
-- 
2.37.1