On Fri, 18 Jul 2014 20:09:44 +0300 Siarhei Siamashka <[email protected]> wrote:
> The Allwinner SoCs support a special FEL boot mode, which can be activated > by users via a button press (or other means). In the FEL mode, the BROM > implements a custom FEL protocol over USB, which allows to upload code to > the device and run it. This protocol had been reverse engineered and > documented by Henrik Nordström: > > http://lists.phcomp.co.uk/pipermail/arm-netbook/2012-June/004341.html > > Because the BROM code is using some parts of the SRAM for itself, only a > few areas are available for use in u-boot. Currently the SPL is loaded > into the "0x2000-0x5cff Free for program use" area and the stack pointer > is at the end of this area. This is barely enough to fit just the current > SPL and leaves almost no headroom for the future code. > > This patch enables the use of a more compact Thumb2 mode for compiling the > FEL SPL binary. And also relocates the stack to another "0x8000-0xbfff Free > for program use" area. Self review. Maybe instead of adding the stack relocation hacks, a better idea would be to just change the usb-boot script to load the SPL to 0x8000 address instead of 0x2000? The relevant usb-boot code is here: https://github.com/linux-sunxi/sunxi-tools/blob/e2a3f16e36f6/usb-boot#L73 In this case the stack would remain in the 0x2000-0x5cff area, and the code/data would use 0x8000-0xbfff. However backwards compatibility with the existing sunxi-tools becomes an issue. Does anyone have any opinion? > Additionally, the BSS segment is cleared. > > Signed-off-by: Siarhei Siamashka <[email protected]> > --- > arch/arm/cpu/armv7/sunxi/Makefile | 1 + > arch/arm/cpu/armv7/sunxi/start_fel.S | 42 > +++++++++++++++++++++++++++++ > arch/arm/cpu/armv7/sunxi/u-boot-spl-fel.lds | 4 +-- > include/configs/sunxi-common.h | 2 -- > 4 files changed, 45 insertions(+), 4 deletions(-) > create mode 100644 arch/arm/cpu/armv7/sunxi/start_fel.S > > diff --git a/arch/arm/cpu/armv7/sunxi/Makefile > b/arch/arm/cpu/armv7/sunxi/Makefile > index a64bfa1..b3eff98 100644 > --- a/arch/arm/cpu/armv7/sunxi/Makefile > +++ b/arch/arm/cpu/armv7/sunxi/Makefile > @@ -21,5 +21,6 @@ ifdef CONFIG_SPL_BUILD > obj-$(CONFIG_SUN7I) += dram.o > ifdef CONFIG_SPL_FEL > obj-y += start.o > +extra-y += start_fel.o > endif > endif > diff --git a/arch/arm/cpu/armv7/sunxi/start_fel.S > b/arch/arm/cpu/armv7/sunxi/start_fel.S > new file mode 100644 > index 0000000..2789fd9 > --- /dev/null > +++ b/arch/arm/cpu/armv7/sunxi/start_fel.S > @@ -0,0 +1,42 @@ > +/* > + * Copyright (c) 2014 Siarhei Siamashka <[email protected]> > + * > + * SPDX-License-Identifier: GPL-2.0+ > + */ > + > +.syntax unified > +.text > +.arm > +.arch armv7a > +.p2align 2 > + > +.globl _start_fel > +.globl s_init > +.globl __bss_start > +.globl __bss_end > + > +_start_fel: > + /* Relocate stack to the 0x8000-0xBFFF area */ > + mov r0, #0xC000 > + str sp, [r0, #-4]! > + str lr, [r0, #-4]! > + adr lr, _exit_fel /* Return back to '_exit_fel' */ > + mov sp, r0 > + > + /* Erase the BSS segment */ > + ldr r0, =__bss_start > + ldr r1, =__bss_end > + mov r2, #0 > +0: cmp r0, r1 > + strbne r2, [r0], #1 > + bne 0b > + > + /* Pass control to the 's_init()' function */ > + b s_init > + > +_exit_fel: > + /* Relocate stack back and return */ > + mov r0, #0xC000 > + ldr sp, [r0, #-4]! > + ldr lr, [r0, #-4]! > + bx lr > diff --git a/arch/arm/cpu/armv7/sunxi/u-boot-spl-fel.lds > b/arch/arm/cpu/armv7/sunxi/u-boot-spl-fel.lds > index 364e35c..418c2fc 100644 > --- a/arch/arm/cpu/armv7/sunxi/u-boot-spl-fel.lds > +++ b/arch/arm/cpu/armv7/sunxi/u-boot-spl-fel.lds > @@ -6,7 +6,7 @@ > */ > OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm") > OUTPUT_ARCH(arm) > -ENTRY(s_init) > +ENTRY(_start_fel) > SECTIONS > { > . = 0x00002000; > @@ -14,7 +14,7 @@ SECTIONS > . = ALIGN(4); > .text : > { > - *(.text.s_init) > + arch/arm/cpu/armv7/sunxi/start_fel.o (.text) > *(.text*) > } > > diff --git a/include/configs/sunxi-common.h b/include/configs/sunxi-common.h > index 5d72d62..4b980e9 100644 > --- a/include/configs/sunxi-common.h > +++ b/include/configs/sunxi-common.h > @@ -18,10 +18,8 @@ > */ > #define CONFIG_SUNXI /* sunxi family */ > #ifdef CONFIG_SPL_BUILD > -#ifndef CONFIG_SPL_FEL > #define CONFIG_SYS_THUMB_BUILD /* Thumbs mode to save space in SPL */ > #endif > -#endif > > #include <asm/arch/cpu.h> /* get chip and board defs */ > -- Best regards, Siarhei Siamashka _______________________________________________ U-Boot mailing list [email protected] http://lists.denx.de/mailman/listinfo/u-boot
