feat(plat/st): add helper to save boot interface

Some parameters from BootROM boot context can be required after boot.
To save space in SYSRAM, this context can be overwritten during images
load sequence. The needed information (here the boot interface) is
then saved in a local variable.

Change-Id: I5e1ad4630ccf78480f415a0a83939005ae67729e
Signed-off-by: Yann Gautier <yann.gautier@foss.st.com>

plat/st/common/include/stm32mp_common.h

@@ -17,6 +17,7 @@
 /* Functions to save and get boot context address given by ROM code */
 void stm32mp_save_boot_ctx_address(uintptr_t address);
 uintptr_t stm32mp_get_boot_ctx_address(void);
+uint16_t stm32mp_get_boot_itf_selected(void);
 
 bool stm32mp_is_single_core(void);
 bool stm32mp_is_closed_device(void);

plat/st/common/stm32mp_common.c

@@ -28,10 +28,14 @@ unsigned int plat_get_syscnt_freq2(void)
 }
 
 static uintptr_t boot_ctx_address;
+static uint16_t boot_itf_selected;
 
 void stm32mp_save_boot_ctx_address(uintptr_t address)
 {
+	boot_api_context_t *boot_context = (boot_api_context_t *)address;
+
 	boot_ctx_address = address;
+	boot_itf_selected = boot_context->boot_interface_selected;
 }
 
 uintptr_t stm32mp_get_boot_ctx_address(void)
@@ -39,6 +43,11 @@ uintptr_t stm32mp_get_boot_ctx_address(void)
 	return boot_ctx_address;
 }
 
+uint16_t stm32mp_get_boot_itf_selected(void)
+{
+	return boot_itf_selected;
+}
+
 uintptr_t stm32mp_ddrctrl_base(void)
 {
 	return DDRCTRL_BASE;