[U-Boot] [PATCH v3 0/6] rockchip: back-to-bootrom: replace assembly-implementation with C-code

[Dr. Philipp Tomsich]

Andy,

Excellent news.
Looks like Heiko and I figured out what breaks the series last week (i.e. the SPL corrupts
the TPL’s stack—so my chaining will break things).

I’ll resubmit without the chained returns later and then we can have a final test tomorrow.

Regards,
Philipp.

> On 25 Sep 2017, at 10:46, Andy Yan <andy.yan at rock-chips.com> wrote:
> 
> Hi Philipp, Heiko:
> 
> 
> I finally got the upstream u-boot run on a rk3188 board which can be attached by DS5 debugger,
> 
> if you have some registers info want to check, please let me know.
> 
> 
> On 2017年09月21日 18:44, Heiko Stübner wrote:
>> Am Donnerstag, 21. September 2017, 12:25:17 CEST schrieb Dr. Philipp Tomsich:
>>>> On 21 Sep 2017, at 11:44, Heiko Stuebner <heiko at sntech.de> wrote:
>>>> 
>>>> Am Donnerstag, 21. September 2017, 11:09:49 CEST schrieb Heiko Stuebner:
>>>>> Am Donnerstag, 21. September 2017, 10:19:23 CEST schrieb Philipp Tomsich:
>>>>>> Recent discussions confirmed (what the code always assumed): the
>>>>>> Rockchip BROM always enters U-Boot with the stack-pointer valid
>>>>>> (i.e. the U-Boot startup code is running off the BROM stack).
>>>>>> 
>>>>>> We can thus replace the back-to-bootrom code (i.e. both the
>>>>>> save_boot_params and back_to_bootrom implementations) using C-code
>>>>>> based on setjmp/longjmp.  The new implementation is already structured
>>>>>> to allow an easy drop-in of Andy's changes to enter download-mode when
>>>>>> returning to the BROM.
>>>>>> 
>>>>>> This turned out to require a some tweaking to system.h (making sure
>>>>>> that the prototype for save_boot_params_ret is visible for A64)and
>>>>>> start.S (so binutils knows that this is a possible function entry and
>>>>>> it can correctly insert A32-to-Thumb transitions) and taking the axe
>>>>>> to setjmp.h (which created quite a few issues with it not expecting
>>>>>> A32/T32/Thumb call-sites and some fragility from GCC being smart about
>>>>>> the clobber-list of the inline assembly... which led to r9 not being
>>>>>> saved or restored).
>>>>> This is missing information on dependant series. Using the
>>>>> u-boot-rockchip
>>>>> repository which is at
>>>>> 782088de7be7 ("rockchip: imply ADC and SARADC_ROCKCHIP on supported
>>>>> SoCs")
>>>>> 
>>>>> patches 1-3 apply, but patch 4 fails to apply as I seem to be missing
>>>>> some
>>>>> dependencies.
>>>>> 
>>>>> And the u-boot mailinglist seems to be configured very strangely, as it
>>>>> seems to rip apart patch-series only sending me some parts.
>>>>> 
>>>>> So far I can at least say, that the u-boot-rockchip repo at the above
>>>>> commit still boots. Could you please point me to mbox versions
>>>>> of needed base patches?
>>>> Also, with patches 1-3 and 5 applied the radxarock board fails to start.
>>>> I see the SPL banner and a "Returning to boot ROM..." and then nothing.
>>>> 
>>>> I do belive it may have something to do with the TPL's + SPL's stack both
>>>> being at the end of SRAM? Having the SPL go back to TPL and then
>>>> back to bootrom was my original intention as well, but didn't work at
>>>> the time.
>>> I didn’t expect the stacks to overlap… so returning from SPL to TPL can’t
>>> work.  However, the jump_to_spl() is at least partially to blame (we already
>>> have a working C-runtime and there’s no point in reentering through the
>>> reset entry-point).
>>> 
>>> I need to ponder this a bit, but my gut feeling is that the TPL->SPL
>>> transition can be done in a less intrusive way and may allow us to retain
>>> the TPL stack.
>> Alternatively, if you can think of an easier solution we could do away with
>> the TPL in its current form. When I did the rk3188 support, this looked like
>> the least-messy way to me, but it really only does the one jump back
>> to the bootrom - so I'm not sure if there isn't simply an easier solution.
>> 
>> And for example the (still wip?) rk3066 series did use spl+tpl in a different
>> way due to bootrom-nand-limitations. rk3066 and rk3188 are quite similar
>> with the rk3066 simply not having the sd-boot capability, so if we want to
>> have nand-boot on rk3188 as well in the future, this may need a different
>> rework again.
>> 
>> 
>> Heiko
>> 
>> 
>> 
> 
>