fel: add Allwinner A523 SoC support

The Allwinner A523 has 128KiB of MCU0 SRAM, which the BootROM will not
touch. The BROM will use some memory in SRAM A2, which it also clears
upon entering FEL mode, starting from address 0x44000. The lowest
allocation seems to be the IRQ stack growing down from 0x45400.
So we won't touch any of that memory, but can freely use the full 128KB
of the primary SRAM for payloads. This means we won't need to swap any
buffers for preserving BROM stacks.
We put the SPL thunk code just below 0x44000, to leave as much SRAM for
the payload as possible.
The rest of the SoC is pretty standard, although the watchdogs are now
in separate MMIO frames, not part of some timer block anymore.

The secure boot mode will prevent even reading the BootROM, so we can
use an address in there to test for the secure boot state. However, even
though a simple "smc #0" will return to its caller, the NS bit is still
set, so we are still in non-secure state afterwards. So leave this bit
out for now until we figure out how to switch to secure state properly.

Signed-off-by: Andre Przywara <osp@andrep.de>

soc_info.c

@@ -162,6 +162,14 @@ sram_swap_buffers f1c100s_sram_swap_buffers[] = {
 	{ .size = 0 }  /* End of the table */
 };
 
+/*
+ * Some SoCs put both stacks, BSS and data segments at the end of a comparably
+ * large SRAM, so we don't need to move anything around.
+ */
+sram_swap_buffers no_sram_swap_buffers[] = {
+	{ .size = 0 }  /* End of the table */
+};
+
 const watchdog_info wd_a10_compat = {
 	.reg_mode = 0x01C20C94,
 	.reg_mode_value = 3,
@@ -187,6 +195,11 @@ const watchdog_info wd_v853_compat = {
 	.reg_mode_value = 0x16aa0001,
 };
 
+const watchdog_info wd_a523_compat = {
+	.reg_mode = 0x02050008,
+	.reg_mode_value = 0x16aa0001,
+};
+
 static const sid_section r40_sid_maps[] = {
 	SID_SECTION("chipid",	0x00, 128),
 	SID_SECTION("in",	0x10, 256),
@@ -539,6 +552,19 @@ soc_info_t soc_info_table[] = {
 		.sid_offset   = 0x200,
 		.sid_sections = generic_2k_sid_maps,
 		.watchdog     = &wd_h6_compat,
+	},{
+		.soc_id       = 0x1890, /* Allwinner A523 */
+		.name         = "A523",
+		.spl_addr     = 0x20000,
+		.scratch_addr = 0x21000,
+		.thunk_addr   = 0x43e00, .thunk_size = 0x200,
+		.swap_buffers = no_sram_swap_buffers,
+		.sram_size    = 144 * 1024,
+		.sid_base     = 0x03006000,
+		.sid_offset   = 0x200,
+		.sid_sections = generic_2k_sid_maps,
+		.rvbar_reg    = 0x08000040,
+		.watchdog     = &wd_a523_compat,
 	},{
 		.swap_buffers = NULL /* End of the table */
 	}