[PATCH V2] firmware: qcom_scm: use the SCM_CONVENTION based on ARM / ARM64

[Kathiravan T]

During SCM probe, to identify the SCM convention, scm call is made with
SMC_CONVENTION_ARM_64 followed by SMC_CONVENTION_ARM_32. Based on the
result what convention to be used is decided.

IPQ chipsets starting from IPQ807x, supports both 32bit and 64bit kernel
variants, however TZ firmware runs in 64bit mode. When running on 32bit
kernel, scm call is made with SMC_CONVENTION_ARM_64 is causing the
system crash, due to the difference in the register sets between ARM and
AARCH64, which is accessed by the TZ.

To avoid this, use SMC_CONVENTION_ARM_64 only on ARM64 builds.

Cc: stable@xxxxxxxxxxxxxxx
Fixes: 9a434cee773a ("firmware: qcom_scm: Dynamically support SMCCC and legacy conventions")
Signed-off-by: Kathiravan T <quic_kathirav@xxxxxxxxxxx>
---
Changes in V2:
	- Added the Fixes tag and cc'd stable mailing list

 drivers/firmware/qcom_scm.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/firmware/qcom_scm.c b/drivers/firmware/qcom_scm.c
index fde33acd46b7..db6754db48a0 100644
--- a/drivers/firmware/qcom_scm.c
+++ b/drivers/firmware/qcom_scm.c
@@ -171,6 +171,7 @@ static enum qcom_scm_convention __get_convention(void)
 	if (likely(qcom_scm_convention != SMC_CONVENTION_UNKNOWN))
 		return qcom_scm_convention;
 
+#if IS_ENABLED(CONFIG_ARM64)
 	/*
 	 * Device isn't required as there is only one argument - no device
 	 * needed to dma_map_single to secure world
@@ -191,6 +192,7 @@ static enum qcom_scm_convention __get_convention(void)
 		forced = true;
 		goto found;
 	}
+#endif
 
 	probed_convention = SMC_CONVENTION_ARM_32;
 	ret = __scm_smc_call(NULL, &desc, probed_convention, &res, true);
-- 
2.17.1