u-boot/arch/arm/cpu/armv7/sunxi/fel_utils.S
Siarhei Siamashka 840fe95c3b sunxi: Support the FEL boot mode in the regular u-boot build
So that the CONFIG_SPL_FEL option is not needed anymore. And the regular
SPL binary, generated by the default u-boot build, is now also bootable
over USB in the FEL mode. The SPL still can boot from the SD card too.

A bunch of system registers need to be saved/restored in order to ensure
that the IRQ handler still works in the BROM FEL code after getting
control back from the SPL. This is done in the sunxi code instead of
abusing ifdefs in 'start.S'.

The decision whether to load the main u-boot binary from the SD card or
return to the FEL code in the BROM is done at runtime.

Signed-off-by: Siarhei Siamashka <siarhei.siamashka@gmail.com>
[hdegoede@redhat.com: Since we now restore various regs before returning to
 the FEL BROM code we can drop the sunxi specific #ifdefs in start.S]
Acked-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
2015-02-16 20:23:52 +01:00

43 lines
951 B
ArmAsm

/*
* Utility functions for FEL mode.
*
* Copyright (c) 2015 Google, Inc
*
* SPDX-License-Identifier: GPL-2.0+
*/
#include <asm-offsets.h>
#include <config.h>
#include <asm/system.h>
#include <linux/linkage.h>
ENTRY(save_boot_params)
ldr r0, =fel_stash
str sp, [r0, #0]
str lr, [r0, #4]
mrs lr, cpsr @ Read CPSR
str lr, [r0, #8]
mrc p15, 0, lr, c1, c0, 0 @ Read CP15 SCTLR Register
str lr, [r0, #12]
mrc p15, 0, lr, c12, c0, 0 @ Read VBAR
str lr, [r0, #16]
mrc p15, 0, lr, c1, c0, 0 @ Read CP15 Control Register
str lr, [r0, #20]
b save_boot_params_ret
ENDPROC(save_boot_params)
ENTRY(return_to_fel)
mov sp, r0
mov lr, r1
ldr r0, =fel_stash
ldr r1, [r0, #20]
mcr p15, 0, r1, c1, c0, 0 @ Write CP15 Control Register
ldr r1, [r0, #16]
mcr p15, 0, r1, c12, c0, 0 @ Write VBAR
ldr r1, [r0, #12]
mcr p15, 0, r1, c1, c0, 0 @ Write CP15 SCTLR Register
ldr r1, [r0, #8]
msr cpsr, r1 @ Write CPSR
bx lr
ENDPROC(return_to_fel)