arm/css/scpi: Don't panic if the SCP fails to respond

Instead, pass back the error to the calling function. This allows
platform code to fall back to another PSCI implementation if
scpi_wait_ready() or a later SCPI command fails.

Signed-off-by: Samuel Holland <samuel@sholland.org>
Change-Id: Ib4411e63c2512857f09ffffe1c405358dddeb4a6

diff --git a/drivers/arm/css/scpi/css_scpi.c b/drivers/arm/css/scpi/css_scpi.c
index c56b7c41bda2f0cd5270bceac04824be65acb6e7..416356bf2a786e6a13d497ccff509d609de5d003 100644 (file)
--- a/drivers/arm/css/scpi/css_scpi.c
+++ b/drivers/arm/css/scpi/css_scpi.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014-2018, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2014-2020, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -51,7 +51,7 @@ static void scpi_secure_message_send(size_t payload_size)
        mhu_secure_message_send(SCPI_MHU_SLOT_ID);
 }
 
-static void scpi_secure_message_receive(scpi_cmd_t *cmd)
+static int scpi_secure_message_receive(scpi_cmd_t *cmd)
 {
        uint32_t mhu_status;
 
@@ -63,7 +63,7 @@ static void scpi_secure_message_receive(scpi_cmd_t *cmd)
        if (mhu_status != (1 << SCPI_MHU_SLOT_ID)) {
                ERROR("MHU: Unexpected protocol (MHU status: 0x%x)\n",
                        mhu_status);
-               panic();
+               return -1;
        }
 
        /*
@@ -74,6 +74,8 @@ static void scpi_secure_message_receive(scpi_cmd_t *cmd)
        dmbld();
 
        memcpy(cmd, (void *) SCPI_SHARED_MEM_SCP_TO_AP, sizeof(*cmd));
+
+       return 0;
 }
 
 static void scpi_secure_message_end(void)
@@ -84,14 +86,19 @@ static void scpi_secure_message_end(void)
 int scpi_wait_ready(void)
 {
        scpi_cmd_t scpi_cmd;
+       int rc;
 
        VERBOSE("Waiting for SCP_READY command...\n");
 
        /* Get a message from the SCP */
        scpi_secure_message_start();
-       scpi_secure_message_receive(&scpi_cmd);
+       rc = scpi_secure_message_receive(&scpi_cmd);
        scpi_secure_message_end();
 
+       /* If no message was received, don't send a response */
+       if (rc != 0)
+               return rc;
+
        /* We are expecting 'SCP Ready', produce correct error if it's not */
        scpi_status_t status = SCP_OK;
        if (scpi_cmd.id != SCPI_CMD_SCP_READY) {
@@ -209,7 +216,8 @@ int scpi_get_css_power_state(unsigned int mpidr, unsigned int *cpu_state_p,
         * Send message and wait for SCP's response
         */
        scpi_secure_message_send(0);
-       scpi_secure_message_receive(&response);
+       if (scpi_secure_message_receive(&response) != 0)
+               goto exit;
 
        if (response.status != SCP_OK)
                goto exit;
@@ -254,7 +262,9 @@ uint32_t scpi_sys_power_state(scpi_system_state_t system_state)
        *payload_addr = system_state & 0xff;
        scpi_secure_message_send(sizeof(*payload_addr));
 
-       scpi_secure_message_receive(&response);
+       /* If no response is received, fill in an error status */
+       if (scpi_secure_message_receive(&response) != 0)
+               response.status = SCP_E_TIMEOUT;
 
        scpi_secure_message_end();