[U-Boot] [PATCH v8 1/3] armv8: Support loading 32-bit OS in AArch32 execution state

[Alexander Graf]

On 11/21/2016 10:48 PM, york sun wrote:
> On 11/21/2016 01:07 PM, Alexander Graf wrote:
>>
>> On 21/11/2016 21:45, york sun wrote:
>>> On 11/21/2016 12:40 PM, Alexander Graf wrote:
>>>>
>>>> On 21/11/2016 21:23, york sun wrote:
>>>>> On 11/09/2016 07:02 PM, Alison Wang wrote:
>>>>>> To support loading a 32-bit OS, the execution state will change from
>>>>>> AArch64 to AArch32 when jumping to kernel.
>>>>>>
>>>>>> The architecture information will be got through checking FIT image,
>>>>>> then U-Boot will load 32-bit OS or 64-bit OS automatically.
>>>>>>
>>>>>> Signed-off-by: Ebony Zhu <ebony.zhu at nxp.com>
>>>>>> Signed-off-by: Alison Wang <alison.wang at nxp.com>
>>>>>> Signed-off-by: Chenhui Zhao <chenhui.zhao at nxp.com>
>>>>>> ---
>>>>>> Changes in v8:
>>>>>> - Fix the issue when U-Boot is running in EL2 or EL1.
>>>>>>
>>>>> Alison,
>>>>>
>>>>> There is a conflict when merging with upstream code. Alex Graf merged
>>>>> his change to support EFI booting. See commit
>>>>> 69bd459d343fe1e5a68a6f187d8c99c78c6fc6ce. Specifically these lines
>>>>>
>>>>>
>>>>>           if (current_el() == 3) {
>>>>>                   smp_kick_all_cpus();
>>>>>                   dcache_disable();
>>>>>                   armv8_switch_to_el2();
>>>>>                   dcache_enable();
>>>>>           }
>>>>>
>>>>> Function armv8_switch_to_el2() didn't take any argument before you
>>>>> change. With your proposed change to support 32-bit OS, you added
>>>>> arguments to this function, and presume this function always load OS.
>>>>> This may be flawed. Would it be possible to keep armv8_switch_to_el2()
>>>>> but introduce another function to carry out switching EL while loading OS?
>>>> Alison introduced it based on my comments - and I'd prefer if we only
>>>> have the function call based version :).
>>>>
>>>> It should be reasonably straight forward to move to it here. Just create
>>>> a new helper stub that enables the dcache and calls entry().
>>>>
>>> Alex,
>>>
>>> Do you always load OS when calling armv8_switch_to_el2()? In this case
>>> of efi booting, kernel entry point needs to be passed to the new
>>> armv8_switch_to_el2 function. The new armv8_switch_to_el2 function
>>> doesn't return, so you cannot continue to run the code.
>> We always call some random function pointer in the new flow. That can be
>> a kernel entry point, but it can also just be a function pointer. In
>> this case, the code would basically look like this:
>>
>> static ulong efi_run_in_el2(ulong (*entry), void *arg1, void *arg2)
>> {
>>       dcache_enable();
>>       return entry(arg1, arg2);
>> }
>>
>> if (current_el() == 3) {
>>       ...
>>       return armv8_switch_to_el2(efi_run_in_el2, entry,
>> &loaded_image_info, &systab);
>> }
>>
> Alex,
>
> Since you are most familiar with EFI boot code, can you send a patch to
> address this? I can squash it with Alison's patch after testing. My
> current test branch is
> http://git.denx.de/?p=u-boot/u-boot-fsl-qoriq.git;a=shortlog;h=refs/heads/test_qoriq.

While trying to fix this up, I ran across another compile breakage:

arch/arm/cpu/armv8/fsl-layerscape/mp.c:114: undefined reference to 
`initiator_type'
arch/arm/cpu/armv8/fsl-layerscape/mp.c:123: undefined reference to 
`initiator_type'


Alex