stm32mp1: add a function to check boot is from serial device

This function will return true if the platform has booted from UART or USB,
false if it booted from a storage device.

Change-Id: I427f87cb3005c337b878430d2d484fb43236d5ea
Signed-off-by: Yann Gautier <yann.gautier@st.com>
Reviewed-on: https://gerrit.st.com/c/mpu/oe/st/tf-a/+/188655


Reviewed-by: CITOOLS <smet-aci-reviews@lists.codex.cro.st.com>
Reviewed-by: Sebastien PASDELOUP <sebastien.pasdeloup-ext@st.com>
Tested-by: Sebastien PASDELOUP <sebastien.pasdeloup-ext@st.com>

plat/st/stm32mp1/include/stm32mp1_private.h

@@ -31,6 +31,7 @@ bool stm32mp1_is_wakeup_from_standby(void);
 
 int stm32_save_boot_interface(uint32_t interface, uint32_t instance);
 int stm32_get_boot_interface(uint32_t *interface, uint32_t *instance);
+bool stm32_boot_is_serial(void);
 
 enum etzpc_decprot_attributes stm32mp_etzpc_binding2decprot(uint32_t mode);
 

plat/st/stm32mp1/stm32mp1_private.c

@@ -843,6 +843,21 @@ int stm32_get_boot_interface(uint32_t *interface, uint32_t *instance)
 	return 0;
 }
 
+bool stm32_boot_is_serial(void)
+{
+	uint32_t boot_itf;
+	uint32_t boot_instance;
+
+	stm32_get_boot_interface(&boot_itf, &boot_instance);
+
+	if ((boot_itf == BOOT_API_CTX_BOOT_INTERFACE_SEL_SERIAL_UART) ||
+	    (boot_itf == BOOT_API_CTX_BOOT_INTERFACE_SEL_SERIAL_USB)) {
+		return true;
+	}
+
+	return false;
+}
+
 #if defined(IMAGE_BL32) && DEBUG
 static const char *const dump_table[] = {
 	"sp_usr  ",