firmware: qcom_scm-64: Improve SMC convention detection

Improve the calling convention detection to use
__qcom_scm_is_call_available() and not blindly assume 32-bit mode if
the checks fails. BUG() if neither 32-bit or 64-bit mode works.

Tested-by: Brian Masney <masneyb@onstation.org> # arm32
Tested-by: Stephan Gerhold <stephan@gerhold.net>
Signed-off-by: Elliot Berman <eberman@codeaurora.org>
Link: https://lore.kernel.org/r/1578431066-19600-9-git-send-email-eberman@codeaurora.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/firmware/qcom_scm-64.c

@@ -336,21 +336,34 @@ int __qcom_scm_ocmem_unlock(struct device *dev, uint32_t id, uint32_t offset,
 
 void __qcom_scm_init(void)
 {
-	u64 cmd;
-	struct arm_smccc_res res;
-	u32 fnid = SCM_SMC_FNID(QCOM_SCM_SVC_INFO, QCOM_SCM_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, fnid);
-
-	arm_smccc_smc(cmd, QCOM_SCM_ARGS(1), cmd & (~BIT(ARM_SMCCC_TYPE_SHIFT)),
-		      0, 0, 0, 0, 0, &res);
+	struct qcom_scm_desc desc = {
+		.svc = QCOM_SCM_SVC_INFO,
+		.cmd = QCOM_SCM_INFO_IS_CALL_AVAIL,
+		.args[0] = SCM_SMC_FNID(QCOM_SCM_SVC_INFO,
+					QCOM_SCM_INFO_IS_CALL_AVAIL) |
+			   (ARM_SMCCC_OWNER_SIP << ARM_SMCCC_OWNER_SHIFT),
+		.arginfo = QCOM_SCM_ARGS(1),
+		.owner = ARM_SMCCC_OWNER_SIP,
+	};
+	struct qcom_scm_res res;
+	int ret;
 
-	if (!res.a0 && res.a1)
-		qcom_smccc_convention = ARM_SMCCC_SMC_64;
-	else
-		qcom_smccc_convention = ARM_SMCCC_SMC_32;
+	qcom_smccc_convention = ARM_SMCCC_SMC_64;
+	// Device isn't required as there is only one argument - no device
+	// needed to dma_map_single to secure world
+	ret = qcom_scm_call_atomic(NULL, &desc, &res);
+	if (!ret && res.result[0] == 1)
+		goto out;
+
+	qcom_smccc_convention = ARM_SMCCC_SMC_32;
+	ret = qcom_scm_call_atomic(NULL, &desc, &res);
+	if (!ret && res.result[0] == 1)
+		goto out;
+
+	qcom_smccc_convention = -1;
+	BUG();
+out:
+	pr_info("QCOM SCM SMC Convention: %lld\n", qcom_smccc_convention);
 }
 
 bool __qcom_scm_pas_supported(struct device *dev, u32 peripheral)