stm32mp: limit size of cacheable DDR in pre-reloc stage

In pre-reloc stage, U-Boot marks cacheable the DDR limited by
the new config CONFIG_DDR_CACHEABLE_SIZE.

This patch allows to avoid any speculative access to DDR protected by
firewall and used by OP-TEE; the "no-map" reserved memory
node in DT are assumed after this limit:
STM32_DDR_BASE + DDR_CACHEABLE_SIZE.

Without security, in basic boot, the value is equal to STM32_DDR_SIZE.
Signed-off-by: NPatrick Delaunay <patrick.delaunay@st.com>
Reviewed-by: NPatrice Chotard <patrice.chotard@st.com>

arch/arm/mach-stm32mp/Kconfig

@@ -93,6 +93,19 @@ config SYS_TEXT_BASE
 config NR_DRAM_BANKS
 	default 1
 
+config DDR_CACHEABLE_SIZE
+	hex "Size of the DDR marked cacheable in pre-reloc stage"
+	default 0x10000000 if TFABOOT
+	default 0x40000000
+	help
+		Define the size of the DDR marked as cacheable in U-Boot
+		pre-reloc stage.
+		This option can be useful to avoid speculatif access
+		to secured area of DDR used by TF-A or OP-TEE before U-Boot
+		initialization.
+		The areas marked "no-map" in device tree should be located
+		before this limit: STM32_DDR_BASE + DDR_CACHEABLE_SIZE.
+
 config SYS_MMCSD_RAW_MODE_U_BOOT_PARTITION_MMC2
 	hex "Partition on MMC2 to use to load U-Boot from"
 	depends on SYS_MMCSD_RAW_MODE_U_BOOT_USE_PARTITION

arch/arm/mach-stm32mp/cpu.c

@@ -230,7 +230,8 @@ static void early_enable_caches(void)
 			round_up(STM32_SYSRAM_SIZE, MMU_SECTION_SIZE),
 			DCACHE_DEFAULT_OPTION);
 	else
-		mmu_set_region_dcache_behaviour(STM32_DDR_BASE, STM32_DDR_SIZE,
+		mmu_set_region_dcache_behaviour(STM32_DDR_BASE,
+						CONFIG_DDR_CACHEABLE_SIZE,
 						DCACHE_DEFAULT_OPTION);
 }
 

arch/arm/mach-stm32mp/spl.c

@@ -138,7 +138,8 @@ void board_init_f(ulong dummy)
 	 * to avoid speculative access and issue in get_ram_size()
 	 */
 	if (!CONFIG_IS_ENABLED(SYS_DCACHE_OFF))
-		mmu_set_region_dcache_behaviour(STM32_DDR_BASE, STM32_DDR_SIZE,
+		mmu_set_region_dcache_behaviour(STM32_DDR_BASE,
+						CONFIG_DDR_CACHEABLE_SIZE,
 						DCACHE_DEFAULT_OPTION);
 }