[PATCH v2 18/23] firmware/psci: Cache PSCI v0.2+ version number to avoid redundant SMCs

[Will Deacon <will@kernel.org>]

Secure monitor calls to EL3 aren't necessarily cheap, so cache the
PSCI version number in memory to avoid asking firmware the same question
over and over again.

Reviewed-by: Jinjie Ruan <ruanjinjie@huawei.com>
Signed-off-by: Will Deacon <will@kernel.org>
---
 drivers/firmware/psci/psci.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
index e73bae6cb23a..8bb3f7c37678 100644
--- a/drivers/firmware/psci/psci.c
+++ b/drivers/firmware/psci/psci.c
@@ -155,7 +155,12 @@ static u32 psci_0_1_get_version(void)
 
 static u32 psci_0_2_get_version(void)
 {
-	return invoke_psci_fn(PSCI_0_2_FN_PSCI_VERSION, 0, 0, 0);
+	static u32 version;
+
+	if (unlikely(!version))
+		version = invoke_psci_fn(PSCI_0_2_FN_PSCI_VERSION, 0, 0, 0);
+
+	return version;
 }
 
 int psci_set_osi_mode(bool enable)
-- 
2.56.0.385.gd3acb90ef8-goog