[U-Boot] [PATCH] ARM: socfpga: Add boot0 hook to prevent SPL corruption

[Dinh Nguyen]

On 11/16/2016 10:54 AM, Marek Vasut wrote:
> Valid Altera SoCFPGA preloader image must contain special data at
> offsets 0x40, 0x44, 0x48 and valid instructions at address 0x4c or
> 0x50. These addresses are by default used by U-Boot's vector table
> and a piece of reset handler, thus a valid preloader corrupts those
> addresses slightly. While this works most of the time, this can and
> does prevent the board from rebooting sometimes and triggering this
> issue may even depend on compiler.
> 
> The problem is that when SoCFPGA performs warm reset, it checks the
> addresses 0x40..0x4b in SRAM for a valid preloader signature and
> header checksum. If those are found, it jumps to address 0x4c or
> 0x50 (this is unclear). These addresses are populated by the first
> few instructions of arch/arm/cpu/armv7/start.S:
> 
> ffff0040 <data_abort>:
> ffff0040:       ebfffffe        bl      ffff0040 <data_abort>
> 
> ffff0044 <reset>:
> ffff0044:       ea000012        b       ffff0094 <save_boot_params>
> 
> ffff0048 <save_boot_params_ret>:
> ffff0048:       e10f0000        mrs     r0, CPSR
> ffff004c:       e200101f        and     r1, r0, #31
> ffff0050:       e331001a        teq     r1, #26
> 
> Without this patch, the CPU will enter the code at 0xffff004c or
> 0xffff0050 , at which point the value of r0 and r1 registers is
> undefined. Moreover, jumping directly to the preloader entry point
> at address 0xffff0000 will also fail, because address 0xffff004.
> is invalid and contains the preloader magic.
> 
> Add BOOT0 hook which reserves the area at offset 0x40..0x5f and
> populates offset 0x50 with jump to the entry point. This way, the
> preloader signature is stored in reserved space and can not corrupt
> the SPL code.
> 
> Signed-off-by: Marek Vasut <marex at denx.de>
> Cc: Chin Liang See <clsee at altera.com>
> Cc: Dinh Nguyen <dinguyen at opensource.altera.com>
> Cc: Stefan Roese <sr at denx.de>
> ---
>  arch/arm/Kconfig                           |  1 +
>  arch/arm/mach-socfpga/include/mach/boot0.h | 28 ++++++++++++++++++++++++++++
>  2 files changed, 29 insertions(+)
>  create mode 100644 arch/arm/mach-socfpga/include/mach/boot0.h

With this patch, I can properly do a soft reset on an Atlas DE0 Nano board.

So feel free to add:

Tested-by: Dinh Nguyen <dinguyen at opensource.altera.com>

Dinh