[U-Boot] [RFC PATCH 0/5] move boot0 hook in the beginning for armv7

Tue Jun 13 18:07:20 UTC 2017

Jagan,

> On 13 Jun 2017, at 19:48, Jagan Teki <jagannadh.teki at gmail.com> wrote:
> 
>>>>>>> 
>>>>>>> On 31 May 2017 at 04:50, Kever Yang <kever.yang at rock-chips.com> wrote:
>>>>>>>> 
>>>>>>>> I think the boot0 hook is suppose to add some data in the very
>>>>>>>> beginning
>>>>>>>> of the SPL image, am I right?
>>>>>>>> 
>>>>>>>> Rockchip SoCs bootrom design is like this:
>>>>>>>> - First 2KB or 4KB internal memory is for bootrom stack and heap;
>>>>>>>> - Then the first 4-byte suppose to be a TAG like 'RK33';
>>>>>>>> - The the following memory address end with '0004' is the first
>>>>>>>>   instruction load and running by bootrom;
>>>>>>>> 
>>>>>>>> Example for RK3288:
>>>>>>>> Before this patch set, the SPL_TEXT_BASE is ff704004, and image write
>>>>>>>> to
>>>>>>>> media device after mkimage like this:
>>>>>>>> 
>>>>>>>> ff704000: 32334b52 00000000 00000000 00000000    RK32............
>>>>>>>> ff704010: 00000000 00000000 00000000 00000000    ................
>>>>>>>> ff704020: ea00000f e59ff014 e59ff014 e59ff014    ................
>>>>>>>> ff704030: e59ff014 e59ff014 e59ff014 e59ff014    ................
>>>>>>>> 
>>>>>>>> Where the first instruction from bootrom is '00000000', which is a
>>>>>>>> undefined instruction.
>>>>>>>> The '_start' and 'reset' have to align to 0x20 for the requirement of
>>>>>>>> VBAR, the memory offset '004'~'01c' are filled with '00000000'.
>>>>>>>> 
>>>>>>>> We can use the boot0 hook to fix this issue, after this patch set,
>>>>>>>> the SPL_TEXT_BASE is ff704000 and image write to media device after
>>>>>>>> mkimage like this:
>>>>>>>> 
>>>>>>>> ff704000: 32334b52 ea00001d e320f000 e320f000    RK32...... ... .
>>>>>>>> ff704010: e320f000 e320f000 e320f000 e320f000    .. ... ... ... .
>>>>>>>> ff704020: ea000016 e59ff014 e59ff014 e59ff014    ................
>>>>>>>> ff704030: e59ff014 e59ff014 e59ff014 e59ff014    ................
>>>>>>>> 
>>>>>>>> The first instruction from bootrom is a 'b reset', and memory of
>>>>>>>> '008'~'01c' are filled with 'nop' instruction.
>>>>>>>> 
>>>>>>>> This patch set does not provide patch for socfpga, bcm and sunxi SoCs
>>>>>>>> which also
>>>>>>>> enable BOOT0_HOOK, so this is a RFC patch, please advice how to make it
>>>>>>>> compatible with those three platforms.
>>>>>>>> 
>>>>>>>> 
>>>>>>>> 
>>>>>>>> Kever Yang (5):
>>>>>>>>   armv7: move boot hook before '_start'
>>>>>>>>   rockchip: boot0: align to 0x20 for armv7 '_start'
>>>>>>>>   rockchip: enable BOOT0_HOOK for SoCs
>>>>>>>>   rockchip: configs: use aligned address for SPL_TEXT_BASE
>>>>>>>>   rockchip: mkimage: use spl_boot0 for all Rockchip SoCs
>>>>>>>> 
>>>>>>>>  arch/arm/include/asm/arch-rockchip/boot0.h |  9 ++++++++-
>>>>>>>>  arch/arm/lib/vectors.S                     | 19 ++++++++++---------
>>>>>>>>  arch/arm/mach-rockchip/Kconfig             |  3 +++
>>>>>>>>  include/configs/rk3036_common.h            |  2 +-
>>>>>>>>  include/configs/rk3288_common.h            |  2 +-
>>>>>>>>  tools/rkcommon.c                           |  8 ++++----
>>>>>>>>  6 files changed, 27 insertions(+), 16 deletions(-)
>>>>>>>> 
>>>>>>>> --
>>>>>>>> 1.9.1
>>>>>>>> 
>>>>>>> Do will still need this series now that (I think) we have a fix for
>>>>>>> the return-to-brom feature in u-boot-rockchip/master?
>>>>>> 
>>>>>> 
>>>>>> Could you point me out exactly which fix do you talking about?
>>>>> 
>>>>> These ones:
>>>>> 
>>>>> a079e52d35 rockchip: mkimage: set init_boot_size to avoid confusing the
>>>>> boot ROM
>>>>> ee2c63912b rockchip: mkimage: force 2KB alignment for init_size
>>>>> 99c700c794 rockchip: mkimage: add support for verify_header/print_header
>>>>> 
>>>>>> This is not about return-to-brom, it's about the first instruction from
>>>>>> Bootrom to SPL.
>>>>>> So this is need for all Rockchip armv7 SoCs.
>>>>> 
>>>>> OK, how did we survive before? What has changed to make this series
>>>>> needed?
>>>> 
>>>> 
>>>> After check with JTAG, I find that I'm wrong with cmd code '00000000',
>>>> this is 'andeq r0, r0, r0', but not undefined in armv7, so it can work.
>>>> 
>>>> I still want this patch set applied because it's better to make all the
>>>> Rockchip's
>>>> SPL have the same format(with 4-byte TAG space reserved), and the ddr binary
>>>> from Rockchip always have pre-padding 4-byte TAG, with this patch set, we
>>>> can replace each other easily and work with one mkimage tool.
>>> 
>>> I'm not sure how to apply this since on the other thread[1] Marek says
>>> it will break socfpga.
>> 
>> To me it looks as if we need to fix the BOOT0 handling across all ARMv7
>> platforms, as it looks as if the current implementation and its documentation
>> contradict each other.
>> 
>> Here’s how BOOT0 was intended:
>> 
>> 1. from Kconfig:
>>          If the SoC's BOOT0 requires a header area filled with (magic)
>>          values, then choose this option, and create a define called
>>          ARM_SOC_BOOT0_HOOK which contains the required assembler
>>          preprocessor code.
>> 
>> 2. from the code in arch/arm/lib/vectors.S:
>> /*
>> * Various SoCs need something special and SoC-specific up front in
>> * order to boot, allow them to set that in their boot0.h file and then
>> * use it here.
>> */
>> 
>> Can we just resolve this by changing arch/arm/lib/vectors.S to replace
>> the entire content starting after the “_start:” label with the BOOT0 hook,
>> if one is defined?
>> This would then make it the responsibiliy of the respective BOOT0 hook
>> to appropriately insert the vectors before or after its other magic and
>> allow all architectures to do whatever their boot ROM requires...
> 
> I don't think placing boot0 hook after _start will resolve (I thought
> you mentioned the same here) and look like placing boot0 hook
> insertion before or after _start results the same based on the
> generated image.I've checked this and find the same 4-byte change in
> hexdump.

I’ll look at what’s going on there. Which defconfig did you try with?

Thanks,
Philipp.