diff --git a/include/drivers/arm/css/scmi.h b/include/drivers/arm/css/scmi.h
index 9dd08e5..356012b 100644
--- a/include/drivers/arm/css/scmi.h
+++ b/include/drivers/arm/css/scmi.h
@@ -168,7 +168,7 @@
 int scmi_ap_core_get_reset_addr(void *p, uint64_t *reset_addr, uint32_t *attr);
 
 /* API to get the platform specific SCMI channel information. */
-scmi_channel_plat_info_t *plat_css_get_scmi_info(int channel_id);
+scmi_channel_plat_info_t *plat_css_get_scmi_info(unsigned int channel_id);
 
 /* API to override default PSCI callbacks for platforms that support SCMI. */
 const plat_psci_ops_t *css_scmi_override_pm_ops(plat_psci_ops_t *ops);
diff --git a/plat/arm/board/juno/juno_topology.c b/plat/arm/board/juno/juno_topology.c
index 075f512..768741e 100644
--- a/plat/arm/board/juno/juno_topology.c
+++ b/plat/arm/board/juno/juno_topology.c
@@ -20,7 +20,7 @@
 		.ring_doorbell = &mhu_ring_doorbell,
 };
 
-scmi_channel_plat_info_t *plat_css_get_scmi_info(int channel_id)
+scmi_channel_plat_info_t *plat_css_get_scmi_info(unsigned int channel_id)
 {
 	return &juno_scmi_plat_info;
 }
diff --git a/plat/arm/board/morello/morello_bl31_setup.c b/plat/arm/board/morello/morello_bl31_setup.c
index a044212..e04587d 100644
--- a/plat/arm/board/morello/morello_bl31_setup.c
+++ b/plat/arm/board/morello/morello_bl31_setup.c
@@ -19,7 +19,7 @@
 	.ring_doorbell = &mhu_ring_doorbell
 };
 
-scmi_channel_plat_info_t *plat_css_get_scmi_info(int channel_id)
+scmi_channel_plat_info_t *plat_css_get_scmi_info(unsigned int channel_id)
 {
 	return &morello_scmi_plat_info;
 }
diff --git a/plat/arm/board/n1sdp/n1sdp_bl31_setup.c b/plat/arm/board/n1sdp/n1sdp_bl31_setup.c
index 5e897fe..ad6c1f8 100644
--- a/plat/arm/board/n1sdp/n1sdp_bl31_setup.c
+++ b/plat/arm/board/n1sdp/n1sdp_bl31_setup.c
@@ -62,7 +62,7 @@
 	0
 };
 
-scmi_channel_plat_info_t *plat_css_get_scmi_info(int channel_id)
+scmi_channel_plat_info_t *plat_css_get_scmi_info(unsigned int channel_id)
 {
 	return &n1sdp_scmi_plat_info;
 }
diff --git a/plat/arm/board/tc/tc_bl31_setup.c b/plat/arm/board/tc/tc_bl31_setup.c
index 0523ef8..2cdf045 100644
--- a/plat/arm/board/tc/tc_bl31_setup.c
+++ b/plat/arm/board/tc/tc_bl31_setup.c
@@ -33,7 +33,7 @@
 	tc_bl31_common_platform_setup();
 }
 
-scmi_channel_plat_info_t *plat_css_get_scmi_info(int channel_id)
+scmi_channel_plat_info_t *plat_css_get_scmi_info(unsigned int channel_id)
 {
 
 	return &tc_scmi_plat_info[channel_id];
diff --git a/plat/arm/css/sgi/sgi_bl31_setup.c b/plat/arm/css/sgi/sgi_bl31_setup.c
index 27cf183..9adcb7c 100644
--- a/plat/arm/css/sgi/sgi_bl31_setup.c
+++ b/plat/arm/css/sgi/sgi_bl31_setup.c
@@ -74,7 +74,7 @@
 	#endif
 };
 
-scmi_channel_plat_info_t *plat_css_get_scmi_info(int channel_id)
+scmi_channel_plat_info_t *plat_css_get_scmi_info(unsigned int channel_id)
 {
 	if (sgi_plat_info.platform_id == RD_N1E1_EDGE_SID_VER_PART_NUM ||
 		sgi_plat_info.platform_id == RD_V1_SID_VER_PART_NUM ||