[RFC PATCH 06/10] powerpc/powernv: opal use new opal call entry point if it exists

[Nicholas Piggin <npiggin@gmail.com>]

OPAL may advertise new endian-specific entry point which has different
calling conventions including using the caller's stack, but otherwise
provides the standard OPAL call API without any changes required to
the OS.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 arch/powerpc/boot/opal.c                   |  5 +++
 arch/powerpc/platforms/powernv/opal-call.c | 36 ++++++++++++++++++++++
 arch/powerpc/platforms/powernv/opal.c      | 30 +++++++++++-------
 3 files changed, 60 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/boot/opal.c b/arch/powerpc/boot/opal.c
index b69818ce592b..8b006a0282ac 100644
--- a/arch/powerpc/boot/opal.c
+++ b/arch/powerpc/boot/opal.c
@@ -13,6 +13,7 @@
 struct opal {
 	u64 base;
 	u64 entry;
+	u64 v4_le_entry;
 } opal;
 
 static u32 opal_con_id;
@@ -75,6 +76,10 @@ static void opal_init(void)
 	if (getprop(opal_node, "opal-entry-address", &opal.entry, sizeof(u64)) < 0)
 		return;
 	opal.entry = be64_to_cpu(opal.entry);
+
+	if (getprop(opal_node, "opal-v4-le-entry-address", &opal.v4_le_entry, sizeof(u64)) < 0)
+		return;
+	opal.v4_le_entry = be64_to_cpu(opal.v4_le_entry);
 }
 
 int opal_console_init(void *devp, struct serial_console_data *scdp)
diff --git a/arch/powerpc/platforms/powernv/opal-call.c b/arch/powerpc/platforms/powernv/opal-call.c
index 506b1798081a..32857254d268 100644
--- a/arch/powerpc/platforms/powernv/opal-call.c
+++ b/arch/powerpc/platforms/powernv/opal-call.c
@@ -92,6 +92,18 @@ static s64 __opal_call_trace(s64 a0, s64 a1, s64 a2, s64 a3,
 #define DO_TRACE false
 #endif /* CONFIG_TRACEPOINTS */
 
+struct opal {
+	u64 base;
+	u64 entry;
+	u64 size;
+	u64 v4_le_entry;
+};
+extern struct opal opal;
+
+typedef int64_t (*opal_v4_le_entry_fn)(uint64_t r3, uint64_t r4, uint64_t r5,
+                               uint64_t r6, uint64_t r7, uint64_t r8,
+                               uint64_t r9, uint64_t r10);
+
 static int64_t opal_call(int64_t a0, int64_t a1, int64_t a2, int64_t a3,
 	     int64_t a4, int64_t a5, int64_t a6, int64_t a7, int64_t opcode)
 {
@@ -99,6 +111,30 @@ static int64_t opal_call(int64_t a0, int64_t a1, int64_t a2, int64_t a3,
 	unsigned long msr = mfmsr();
 	bool mmu = (msr & (MSR_IR|MSR_DR));
 	int64_t ret;
+	opal_v4_le_entry_fn fn;
+
+	if (IS_ENABLED(CONFIG_CPU_LITTLE_ENDIAN))
+		fn = (opal_v4_le_entry_fn)(opal.v4_le_entry);
+
+	if (fn) {
+		if (!mmu) {
+			BUG_ON(msr & MSR_EE);
+			ret = fn(opcode, a0, a1, a2, a3, a4, a5, a6);
+			return ret;
+		}
+
+		local_irq_save(flags);
+		hard_irq_disable(); /* XXX r13 */
+		msr &= ~MSR_EE;
+		mtmsr(msr & ~(MSR_IR|MSR_DR));
+
+		ret = fn(opcode, a0, a1, a2, a3, a4, a5, a6);
+
+		mtmsr(msr);
+		local_irq_restore(flags);
+
+		return ret;
+	}
 
 	msr &= ~MSR_EE;
 
diff --git a/arch/powerpc/platforms/powernv/opal.c b/arch/powerpc/platforms/powernv/opal.c
index a0e9808237b2..d00772d40680 100644
--- a/arch/powerpc/platforms/powernv/opal.c
+++ b/arch/powerpc/platforms/powernv/opal.c
@@ -46,13 +46,14 @@ static DEFINE_SPINLOCK(msg_list_lock);
 static LIST_HEAD(msg_list);
 
 /* /sys/firmware/opal */
-struct kobject *opal_kobj;
+struct kobject *opal_kobj __read_mostly;
 
 struct opal {
 	u64 base;
 	u64 entry;
 	u64 size;
-} opal;
+	u64 v4_le_entry;
+} opal __read_mostly;
 
 struct mcheck_recoverable_range {
 	u64 start_addr;
@@ -150,14 +151,15 @@ unsigned long arch_symbol_lookup_name(const char *name)
 int __init early_init_dt_scan_opal(unsigned long node,
 				   const char *uname, int depth, void *data)
 {
-	const void *basep, *entryp, *sizep;
-	int basesz, entrysz, runtimesz;
+	const void *basep, *entryp, *v4_le_entryp, *sizep;
+	int basesz, entrysz, v4_le_entrysz, runtimesz;
 
 	if (depth != 1 || strcmp(uname, "ibm,opal") != 0)
 		return 0;
 
 	basep  = of_get_flat_dt_prop(node, "opal-base-address", &basesz);
 	entryp = of_get_flat_dt_prop(node, "opal-entry-address", &entrysz);
+	v4_le_entryp = of_get_flat_dt_prop(node, "opal-v4-le-entry-address", &v4_le_entrysz);
 	sizep = of_get_flat_dt_prop(node, "opal-runtime-size", &runtimesz);
 
 	if (!basep || !entryp || !sizep)
@@ -166,19 +168,25 @@ int __init early_init_dt_scan_opal(unsigned long node,
 	opal.base = of_read_number(basep, basesz/4);
 	opal.entry = of_read_number(entryp, entrysz/4);
 	opal.size = of_read_number(sizep, runtimesz/4);
+	opal.v4_le_entry = of_read_number(v4_le_entryp, v4_le_entrysz/4);
+
+	if (of_flat_dt_is_compatible(node, "ibm,opal-v3")) {
+		powerpc_firmware_features |= FW_FEATURE_OPAL;
+		pr_debug("OPAL detected !\n");
+	} else {
+		panic("OPAL v3 compatible firmware not detected, can not continue.\n");
+	}
 
 	pr_debug("OPAL Base  = 0x%llx (basep=%p basesz=%d)\n",
 		 opal.base, basep, basesz);
-	pr_debug("OPAL Entry = 0x%llx (entryp=%p basesz=%d)\n",
+	pr_debug("OPAL Entry = 0x%llx (entryp=%p entrysz=%d)\n",
 		 opal.entry, entryp, entrysz);
-	pr_debug("OPAL Entry = 0x%llx (sizep=%p runtimesz=%d)\n",
+	pr_debug("OPAL Size = 0x%llx (sizep=%p runtimesz=%d)\n",
 		 opal.size, sizep, runtimesz);
+	if (IS_ENABLED(CONFIG_CPU_LITTLE_ENDIAN) && v4_le_entryp) {
 
-	if (of_flat_dt_is_compatible(node, "ibm,opal-v3")) {
-		powerpc_firmware_features |= FW_FEATURE_OPAL;
-		pr_debug("OPAL detected !\n");
-	} else {
-		panic("OPAL != V3 detected, no longer supported.\n");
+		pr_debug("OPAL v4 Entry = 0x%llx (v4_le_entryp=%p v4_le_entrysz=%d)\n",
+			 opal.v4_le_entry, v4_le_entryp, v4_le_entrysz);
 	}
 
 	return 1;
-- 
2.23.0