[RFC 09/17] firmware: qcom_scm-64: Improve SMC convention detection

[Elliot Berman <eberman@codeaurora.org>]

- Use enum to describe SMC convention.
- Improve SMC convention detection to use __qcom_scm_is_call_available
  instead of circumventing qcom_scm_call_smccc.
- Improve SMC convention detection to check that SMCCC-32 works, instead
  of just assuming it does of SMCCC-64 does not.

Signed-off-by: Elliot Berman <eberman@codeaurora.org>
---
 drivers/firmware/qcom_scm-64.c | 38 +++++++++++++++++++++-----------------
 1 file changed, 21 insertions(+), 17 deletions(-)

diff --git a/drivers/firmware/qcom_scm-64.c b/drivers/firmware/qcom_scm-64.c
index c83eb1d..4d7fd3e 100644
--- a/drivers/firmware/qcom_scm-64.c
+++ b/drivers/firmware/qcom_scm-64.c
@@ -58,7 +58,13 @@ struct arm_smccc_args {
 	unsigned long a[8];
 };
 
-static u64 qcom_smccc_convention = -1;
+enum qcom_smc_convention {
+	SMC_CONVENTION_UNKNOWN,
+	SMC_CONVENTION_ARM_32,
+	SMC_CONVENTION_ARM_64,
+};
+
+static enum qcom_smc_convention qcom_smc_convention = SMC_CONVENTION_UNKNOWN;
 static DEFINE_MUTEX(qcom_scm_lock);
 
 #define QCOM_SCM_EBUSY_WAIT_MS 30
@@ -103,7 +109,9 @@ static int ___qcom_scm_call_smccc(struct device *dev,
 
 	smc.a[0] = ARM_SMCCC_CALL_VAL(
 		atomic ? ARM_SMCCC_FAST_CALL : ARM_SMCCC_STD_CALL,
-		qcom_smccc_convention,
+		(qcom_smc_convention == SMC_CONVENTION_ARM_64) ?
+			ARM_SMCCC_SMC_64 :
+			ARM_SMCCC_SMC_32,
 		desc->owner,
 		SMCCC_FUNCNUM(desc->svc, desc->cmd));
 	smc.a[1] = desc->arginfo;
@@ -117,7 +125,7 @@ static int ___qcom_scm_call_smccc(struct device *dev,
 		if (!args_virt)
 			return -ENOMEM;
 
-		if (qcom_smccc_convention == ARM_SMCCC_SMC_32) {
+		if (qcom_smc_convention == SMC_CONVENTION_ARM_32) {
 			__le32 *args = args_virt;
 
 			for (i = 0; i < SMCCC_N_EXT_ARGS; i++)
@@ -579,19 +587,15 @@ int __qcom_scm_qsmmu500_wait_safe_toggle(struct device *dev, bool en)
 
 void __qcom_scm_init(void)
 {
-	u64 cmd;
-	struct arm_smccc_res res;
-	u32 function = SMCCC_FUNCNUM(QCOM_SCM_SVC_INFO, QCOM_INFO_IS_CALL_AVAIL);
-
 	/* First try a SMC64 call */
-	cmd = ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, ARM_SMCCC_SMC_64,
-				 ARM_SMCCC_OWNER_SIP, function);
-
-	arm_smccc_smc(cmd, QCOM_SCM_ARGS(1), cmd & (~BIT(ARM_SMCCC_TYPE_SHIFT)),
-		      0, 0, 0, 0, 0, &res);
-
-	if (!res.a0 && res.a1)
-		qcom_smccc_convention = ARM_SMCCC_SMC_64;
-	else
-		qcom_smccc_convention = ARM_SMCCC_SMC_32;
+	qcom_smc_convention = SMC_CONVENTION_ARM_64;
+	if (__qcom_scm_is_call_available(NULL, QCOM_SCM_SVC_INFO,
+					 QCOM_INFO_IS_CALL_AVAIL) <= 0) {
+		/* Now try a SMC32 call */
+		qcom_smc_convention = SMC_CONVENTION_ARM_32;
+		if (__qcom_scm_is_call_available(NULL, QCOM_SCM_SVC_INFO,
+						 QCOM_INFO_IS_CALL_AVAIL) <= 0) {
+			qcom_smc_convention = SMC_CONVENTION_UNKNOWN;
+		}
+	}
 }
-- 
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