firmware: qcom: scm: smc: Handle missing SCM device

BugLink: https://bugs.launchpad.net/bugs/2104873

[ Upstream commit 94f48ec ]

Commit ca61d68 ("firmware: qcom: scm: fix a NULL-pointer
dereference") makes it explicit that qcom_scm_get_tzmem_pool() can
return NULL, therefore its users should handle this.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Link: https://lore.kernel.org/r/20241209-qcom-scm-missing-barriers-and-all-sort-of-srap-v2-5-9061013c8d92@linaro.org
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Noah Wager <noah.wager@canonical.com>

Author: krzk

drivers/firmware/qcom/qcom_scm-smc.c

@@ -173,6 +173,9 @@ int __scm_smc_call(struct device *dev, const struct qcom_scm_desc *desc,
 		smc.args[i + SCM_SMC_FIRST_REG_IDX] = desc->args[i];
 
 	if (unlikely(arglen > SCM_SMC_N_REG_ARGS)) {
+		if (!mempool)
+			return -EINVAL;
+
 		args_virt = qcom_tzmem_alloc(mempool,
 					     SCM_SMC_N_EXT_ARGS * sizeof(u64),
 					     flag);