The SCU firmware does NOT always have return value stored in message
header's function element even the API has response data, those special
APIs are defined as void function in SCU firmware, so they should be
treated as return success always.

Signed-off-by: Anson Huang <redacted>
---
	- This patch is based on the patch of https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpatchwork.kernel.org%2Fpatch%2F11129553%2F&amp;data=02%7C01%7Cleonard.crestez%40nxp.com%7Cc0ced6cd07f04023977008d741a07367%7C686ea1d3bc2b4c6fa92cd99c5c301635%7C0%7C0%7C637050029712216472&amp;sdata=Ccq%2Fb2RJdMqmnL7VXrl8YhOlUwC7bWiUG%2BNmiw4OsSM%3D&amp;reserved=0
---
  drivers/firmware/imx/imx-scu.c | 34 ++++++++++++++++++++++++++++++++--
  1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/drivers/firmware/imx/imx-scu.c b/drivers/firmware/imx/imx-scu.c
index 869be7a..ced5b12 100644
--- a/drivers/firmware/imx/imx-scu.c
+++ b/drivers/firmware/imx/imx-scu.c

@@ -78,6 +78,11 @@ static int imx_sc_linux_errmap[IMX_SC_ERR_LAST] = {
  	-EIO,	 /* IMX_SC_ERR_FAIL */
  };
  
+static const struct imx_sc_rpc_msg whitelist[] = {
+	{ .svc = IMX_SC_RPC_SVC_MISC, .func = IMX_SC_MISC_FUNC_UNIQUE_ID },
+	{ .svc = IMX_SC_RPC_SVC_MISC, .func = IMX_SC_MISC_FUNC_GET_BUTTON_STATUS },
+};

+
  static struct imx_sc_ipc *imx_sc_ipc_handle;
  
  static inline int imx_sc_to_linux_errno(int errno)

@@ -157,11 +162,24 @@ static int imx_scu_ipc_write(struct imx_sc_ipc *sc_ipc, void *msg)
  	return 0;
  }
  
+static bool imx_scu_call_skip_return_value_check(uint8_t svc, uint8_t func)
+{
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(whitelist); i++)
+		if (svc == whitelist[i].svc &&
+			func == whitelist[i].func)
+			return true;
+
+	return false;
+}
+
  /*
   * RPC command/response
   */
  int imx_scu_call_rpc(struct imx_sc_ipc *sc_ipc, void *msg, bool have_resp)
  {
+	uint8_t saved_svc, saved_func;
  	struct imx_sc_rpc_msg *hdr;
  	int ret;
  

@@ -171,8 +189,11 @@ int imx_scu_call_rpc(struct imx_sc_ipc *sc_ipc, void *msg, bool have_resp)
  	mutex_lock(&sc_ipc->lock);
  	reinit_completion(&sc_ipc->done);
  
-	if (have_resp)
+	if (have_resp) {
  		sc_ipc->msg = msg;
+		saved_svc = ((struct imx_sc_rpc_msg *)msg)->svc;
+		saved_func = ((struct imx_sc_rpc_msg *)msg)->func;
+	}
  	sc_ipc->count = 0;
  	ret = imx_scu_ipc_write(sc_ipc, msg);
  	if (ret < 0) {

@@ -190,7 +211,16 @@ int imx_scu_call_rpc(struct imx_sc_ipc *sc_ipc, void *msg, bool have_resp)
  
  		/* response status is stored in hdr->func field */
  		hdr = msg;
-		ret = hdr->func;
+		/*
+		 * Some special SCU firmware APIs do NOT have return value
+		 * in hdr->func, but they do have response data, those special
+		 * APIs are defined as void function in SCU firmware, so they
+		 * should be treated as return success always.
+		 */
+		if (!imx_scu_call_skip_return_value_check(saved_svc, saved_func))
+			ret = hdr->func;
+		else
+			ret = 0;
  	}
  
  out: