[U-Boot] [PATCH v2 3/3] sunxi: Normalise FEL support

Siarhei Siamashka siarhei.siamashka at gmail.com
Sun Feb 8 04:48:26 CET 2015


On Sat,  7 Feb 2015 10:47:30 -0700
Simon Glass <sjg at chromium.org> wrote:

> Make sunxi's FEL code fit with the normal U-Boot boot sequence instead of
> creating its own. There are some #ifdefs required in start.S. Future work
> will hopefully remove these.
> 
> This series is available at u-boot-dm, branch sunxi-working.
> 
> Signed-off-by: Simon Glass <sjg at chromium.org>
> ---
> 
> Changes in v2:
> - Adjust for new save_boot_params() API
> - Drop patch to change r0 to r2 in start.S
> - Add #ifdefs to start.S to deal with FEL
> - Use 'Fast Early Loader' as the full name for FEL

Thanks for working on these patches. It looks like we are finally
getting really close to resolving the sunxi FEL boot problem.

Some comments are below.

>  arch/arm/cpu/armv7/start.S                  |  5 +-
>  arch/arm/cpu/armv7/sunxi/Makefile           |  4 +-
>  arch/arm/cpu/armv7/sunxi/board.c            | 21 ++++++++
>  arch/arm/cpu/armv7/sunxi/config.mk          |  2 -
>  arch/arm/cpu/armv7/sunxi/fel_utils.S        | 25 +++++++++
>  arch/arm/cpu/armv7/sunxi/u-boot-spl-fel.lds | 82 -----------------------------
>  arch/arm/include/asm/arch-sunxi/sys_proto.h | 10 ++++
>  board/sunxi/Kconfig                         | 10 ++++
>  include/configs/sunxi-common.h              |  6 +--
>  scripts/Makefile.spl                        |  2 -
>  10 files changed, 73 insertions(+), 94 deletions(-)
>  create mode 100644 arch/arm/cpu/armv7/sunxi/fel_utils.S
>  delete mode 100644 arch/arm/cpu/armv7/sunxi/u-boot-spl-fel.lds
> 
> diff --git a/arch/arm/cpu/armv7/start.S b/arch/arm/cpu/armv7/start.S
> index 9b49ece..098a83a 100644
> --- a/arch/arm/cpu/armv7/start.S
> +++ b/arch/arm/cpu/armv7/start.S
> @@ -54,7 +54,8 @@ save_boot_params_ret:
>   * (OMAP4 spl TEXT_BASE is not 32 byte aligned.
>   * Continue to use ROM code vector only in OMAP4 spl)
>   */
> -#if !(defined(CONFIG_OMAP44XX) && defined(CONFIG_SPL_BUILD))
> +#if !(defined(CONFIG_OMAP44XX) && defined(CONFIG_SPL_BUILD)) && \
> +		!defined(CONFIG_SPL_FEL)

Maybe we can just update the 'save_boot_params' function to save the
important configuration registers and then undo this configuration
in 'return_to_fel'? This allows us to avoid the sunxi specific ifdefs
in the core ARM code.

In this particular case, restoring VBAR and CPSR is important because
the BROM code uses an IRQ handler for FEL (presumably USB related).
And we want to ensure that this IRQ handler works properly again
after resuming the FEL code.

>  	/* Set V=0 in CP15 SCTLR register - for VBAR to point to vector */
>  	mrc	p15, 0, r0, c1, c0, 0	@ Read CP15 SCTLR Register
>  	bic	r0, #CR_V		@ V = 0
> @@ -67,7 +68,9 @@ save_boot_params_ret:
>  
>  	/* the mask ROM code should have PLL and others stable */
>  #ifndef CONFIG_SKIP_LOWLEVEL_INIT
> +#ifndef CONFIG_SPL_FEL

Same here.

>  	bl	cpu_init_cp15
> +#endif
>  	bl	cpu_init_crit
>  #endif
>  
> diff --git a/arch/arm/cpu/armv7/sunxi/Makefile b/arch/arm/cpu/armv7/sunxi/Makefile
> index 48db744..c1b975a 100644
> --- a/arch/arm/cpu/armv7/sunxi/Makefile
> +++ b/arch/arm/cpu/armv7/sunxi/Makefile
> @@ -38,7 +38,5 @@ obj-$(CONFIG_MACH_SUN5I)	+= dram_sun4i.o
>  obj-$(CONFIG_MACH_SUN6I)	+= dram_sun6i.o
>  obj-$(CONFIG_MACH_SUN7I)	+= dram_sun4i.o
>  obj-$(CONFIG_MACH_SUN8I)	+= dram_sun8i.o
> -ifdef CONFIG_SPL_FEL
> -obj-y	+= start.o
> -endif
> +obj-y	+= fel_utils.o
>  endif
> diff --git a/arch/arm/cpu/armv7/sunxi/board.c b/arch/arm/cpu/armv7/sunxi/board.c
> index 6e28bcd..b7492ac 100644
> --- a/arch/arm/cpu/armv7/sunxi/board.c
> +++ b/arch/arm/cpu/armv7/sunxi/board.c
> @@ -27,6 +27,13 @@
>  
>  #include <linux/compiler.h>
>  
> +struct fel_stash {
> +	uint32_t sp;
> +	uint32_t lr;
> +};

struct fel_stash {
	uint32_t sp;
	uint32_t lr;
	uint32_t cpsr;
	uint32_t sctlr;
	uint32_t vbar;
	uint32_t cr;
};

> +struct fel_stash fel_stash __attribute__((section(".data")));
> +
>  static int gpio_init(void)
>  {
>  #if CONFIG_CONS_INDEX == 1 && defined(CONFIG_UART0_PORT_F)
> @@ -65,6 +72,12 @@ static int gpio_init(void)
>  	return 0;
>  }
>  
> +void spl_board_load_image(void)
> +{
> +	debug("Returning to FEL sp=%x, lr=%x\n", fel_stash.sp, fel_stash.lr);
> +	return_to_fel(fel_stash.sp, fel_stash.lr);
> +}
> +
>  void s_init(void)
>  {
>  #if defined CONFIG_MACH_SUN6I || defined CONFIG_MACH_SUN8I
> @@ -95,6 +108,14 @@ void s_init(void)
>   */
>  u32 spl_boot_device(void)
>  {
> +	/*
> +	 * Have we been asked to return to the FEL portion of the boot ROM?
> +	 * TODO: We need a more robust test here, or bracket this with
> +	 * #ifdef CONFIG_SPL_FEL.
> +	 */
> +	if (fel_stash.lr >= 0xffff0000 && fel_stash.lr < 0xffff4000)
> +		return BOOT_DEVICE_BOARD;
>  	return BOOT_DEVICE_MMC1;

It is probably better to do it this way:

#ifdef CONFIG_SPL_FEL
	return BOOT_DEVICE_BOARD;
#else
	if (memcmp((void *)4, "eGON.BT0", 8) == 0)
		return BOOT_DEVICE_MMC1;
	else
		return BOOT_DEVICE_BOARD;
#endif

The memcmp (or equivalent code) ensures that it is compatible with
    https://github.com/ssvb/sunxi-tools/commit/aa7e1880986e5c9a825b08aed9dc5621b821805f

Then the new 'fel spl u-boot-sunxi-with-spl.bin' command for loading
and executing the SPL works fine without CONFIG_SPL_FEL defined
(because the SD card specific "eGON.BT0" signature is replaced with
the "eGON.FEL" signature by the 'fel' tool in the device memory
before transferring control to the SPL code). Needless to say that
the SPL built this way still works when written to the SD card.

And if CONFIG_SPL_FEL is defined, then the FEL support still works in a
legacy way (via 'fel write 0x2000 u-boot-spl.bin; fel exe 0x2000').

We would only need to drop the legacy way in u-boot v2015.07 if the
new one proves to be problem free by that time :-)


>  }
>  
> diff --git a/arch/arm/cpu/armv7/sunxi/config.mk b/arch/arm/cpu/armv7/sunxi/config.mk
> index 00f5ffc..76ffec9 100644
> --- a/arch/arm/cpu/armv7/sunxi/config.mk
> +++ b/arch/arm/cpu/armv7/sunxi/config.mk
> @@ -1,8 +1,6 @@
>  # Build a combined spl + u-boot image
>  ifdef CONFIG_SPL
>  ifndef CONFIG_SPL_BUILD
> -ifndef CONFIG_SPL_FEL
>  ALL-y += u-boot-sunxi-with-spl.bin
>  endif
>  endif
> -endif
> diff --git a/arch/arm/cpu/armv7/sunxi/fel_utils.S b/arch/arm/cpu/armv7/sunxi/fel_utils.S
> new file mode 100644
> index 0000000..0c1de52
> --- /dev/null
> +++ b/arch/arm/cpu/armv7/sunxi/fel_utils.S
> @@ -0,0 +1,25 @@
> +/*
> + * 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]
> +	b	save_boot_params_ret
> +ENDPROC(save_boot_params)
> +
> +ENTRY(return_to_fel)
> +	mov	sp, r0
> +	mov	lr, r1
> +	bx	lr
> +ENDPROC(return_to_fel)

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
	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
	str	lr, [r0, #20]
	b	save_boot_params_ret
ENDPROC(save_boot_params)

ENTRY(return_to_fel)
	ldr	r0, =fel_stash
	ldr	lr, [r0, #20]
	mcr	p15, 0, lr, c1, c0, 0	@ Write CP15 Control
	ldr	lr, [r0, #16]
	mcr	p15, 0, lr, c12, c0, 0	@ Write VBAR
	ldr	lr, [r0, #12]
	mcr	p15, 0, lr, c1, c0, 0	@ Write CP15 SCTLR
	ldr	lr, [r0, #8]
	msr	cpsr, lr		@ Write CPSR
	ldr	sp, [r0, #0]
	ldr	lr, [r0, #4]
	bx	lr
ENDPROC(return_to_fel)


This seems to work for me. However we probably might try to skip
restoring some of these registers. Also somebody might want to
review the order in which the registers should be restored.

> diff --git a/arch/arm/cpu/armv7/sunxi/u-boot-spl-fel.lds b/arch/arm/cpu/armv7/sunxi/u-boot-spl-fel.lds
> deleted file mode 100644
> index 928b7c1..0000000
> --- a/arch/arm/cpu/armv7/sunxi/u-boot-spl-fel.lds
> +++ /dev/null
> @@ -1,82 +0,0 @@
> -/*
> - * (C) Copyright 2013
> - * Henrik Nordstrom <henrik at henriknordstrom.net>
> - *
> - * SPDX-License-Identifier:	GPL-2.0+
> - */
> -OUTPUT_FORMAT("elf32-littlearm", "elf32-littlearm", "elf32-littlearm")
> -OUTPUT_ARCH(arm)
> -ENTRY(s_init)
> -SECTIONS
> -{
> -	. = 0x00002000;
> -
> -	. = ALIGN(4);
> -	.text :
> -	{
> -		*(.text.s_init)
> -		*(.text*)
> -	}
> -
> -	. = ALIGN(4);
> -	.rodata : { *(SORT_BY_ALIGNMENT(SORT_BY_NAME(.rodata*))) }
> -
> -	. = ALIGN(4);
> -	.data : {
> -		*(.data*)
> -	}
> -
> -	. = ALIGN(4);
> -	.u_boot_list : {
> -		KEEP(*(SORT(.u_boot_list*)));
> -	}
> -
> -	. = ALIGN(4);
> -	. = .;
> -
> -	. = ALIGN(4);
> -	.rel.dyn : {
> -		__rel_dyn_start = .;
> -		*(.rel*)
> -		__rel_dyn_end = .;
> -	}
> -
> -	.dynsym : {
> -		__dynsym_start = .;
> -		*(.dynsym)
> -	}
> -
> -	. = ALIGN(4);
> -	.note.gnu.build-id :
> -	{
> -		*(.note.gnu.build-id)
> -	}
> -	_end = .;
> -
> -	. = ALIGN(4096);
> -	.mmutable : {
> -		*(.mmutable)
> -	}
> -
> -	.bss_start __rel_dyn_start (OVERLAY) : {
> -		KEEP(*(.__bss_start));
> -		__bss_base = .;
> -	}
> -
> -	.bss __bss_base (OVERLAY) : {
> -		*(.bss*)
> -		. = ALIGN(4);
> -		__bss_limit = .;
> -	}
> -
> -	.bss_end __bss_limit (OVERLAY) : {
> -		KEEP(*(.__bss_end));
> -	}
> -
> -	/DISCARD/ : { *(.dynstr*) }
> -	/DISCARD/ : { *(.dynamic*) }
> -	/DISCARD/ : { *(.plt*) }
> -	/DISCARD/ : { *(.interp*) }
> -	/DISCARD/ : { *(.gnu*) }
> -	/DISCARD/ : { *(.note*) }
> -}
> diff --git a/arch/arm/include/asm/arch-sunxi/sys_proto.h b/arch/arm/include/asm/arch-sunxi/sys_proto.h
> index c3e636e..60a5bd8 100644
> --- a/arch/arm/include/asm/arch-sunxi/sys_proto.h
> +++ b/arch/arm/include/asm/arch-sunxi/sys_proto.h
> @@ -13,4 +13,14 @@
>  
>  void sdelay(unsigned long);
>  
> +/* return_to_fel() - Return to BROM from SPL
> + *
> + * This returns back into the BROM after U-Boot SPL has performed its initial
> + * init. It uses the provided lr and sp to do so.
> + *
> + * @lr:		BROM link register value (return address)
> + * @sp:		BROM stack pointer
> + */
> +void return_to_fel(uint32_t lr, uint32_t sp);
> +
>  #endif
> diff --git a/board/sunxi/Kconfig b/board/sunxi/Kconfig
> index 4a21589..3eab81f 100644
> --- a/board/sunxi/Kconfig
> +++ b/board/sunxi/Kconfig
> @@ -149,6 +149,16 @@ config SPL_FEL
>  	bool "SPL/FEL mode support"
>  	depends on SPL
>  	default n
> +	help
> +	  This enables support for Fast Early Loader (FEL) mode. This
> +	  allows U-Boot to be loaded to the board over USB by the on-chip
> +	  boot rom. U-Boot should be sent in two parts: SPL first, with
> +	  'fel write 0x2000 u-boot-spl.bin; fel exe 0x2000' then U-Boot with
> +	  'fel write 0x4a000000 u-boot.bin; fel exe 0x4a000000'. This option
> +	  shrinks the amount of SRAM available to SPL, so only enable it if
> +	  you need FEL. Note that enabling this option only allows FEL to be
> +	  used; it is still possible to boot U-Boot from boot media. U-Boot
> +	  SPL detects when it is being loaded using FEL.
>  
>  config UART0_PORT_F
>  	bool "UART0 on MicroSD breakout board"
> diff --git a/include/configs/sunxi-common.h b/include/configs/sunxi-common.h
> index 6cfd7e1..3becb4f 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 */
>  
> @@ -146,10 +144,10 @@
>  #define CONFIG_SPL_SERIAL_SUPPORT
>  #define CONFIG_SPL_LIBGENERIC_SUPPORT
>  
> +#define CONFIG_SPL_BOARD_LOAD_IMAGE
> +
>  #ifdef CONFIG_SPL_FEL
>  
> -#define CONFIG_SPL_LDSCRIPT "arch/arm/cpu/armv7/sunxi/u-boot-spl-fel.lds"
> -#define CONFIG_SPL_START_S_PATH "arch/arm/cpu/armv7/sunxi"
>  #define CONFIG_SPL_TEXT_BASE		0x2000
>  #define CONFIG_SPL_MAX_SIZE		0x4000		/* 16 KiB */
>  
> diff --git a/scripts/Makefile.spl b/scripts/Makefile.spl
> index ecf3037..5a1962b 100644
> --- a/scripts/Makefile.spl
> +++ b/scripts/Makefile.spl
> @@ -153,10 +153,8 @@ ALL-y	+= $(obj)/$(BOARD)-spl.bin
>  endif
>  
>  ifdef CONFIG_SUNXI
> -ifndef CONFIG_SPL_FEL
>  ALL-y	+= $(obj)/sunxi-spl.bin
>  endif
> -endif
>  
>  ifeq ($(CONFIG_SYS_SOC),"at91")
>  ALL-y	+= boot.bin

One more theoretical concern is the placement of the stack in the legacy
FEL mode after your changes. Now it seems to be moved to 0x8000, which
might be fine though, according to the memory map from

    https://github.com/hno/Allwinner-Info/blob/master/FEL-usb/USB-protocol.txt

If we want to preserve the old behaviour, then we would need to place
it around 0x5d00.

-- 
Best regards,
Siarhei Siamashka


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