[RFC PATCH kernel] powerpc: Fix early setup to make early_ioremap work

[Christophe Leroy]

Le 20/05/2021 à 07:52, Alexey Kardashevskiy a écrit :
> 
> 
> On 20/05/2021 15:46, Christophe Leroy wrote:
>>
>>
>> Le 20/05/2021 à 05:29, Alexey Kardashevskiy a écrit :
>>> The immediate problem is that after
>>> 0bd3f9e953bd ("powerpc/legacy_serial: Use early_ioremap()")
>>> the kernel silently reboots. The reason is that early_ioremap() returns
>>> broken addresses as it uses slot_virt[] array which initialized with
>>> offsets from FIXADDR_TOP == IOREMAP_END+FIXADDR_SIZE ==
>>> KERN_IO_END- FIXADDR_SIZ + FIXADDR_SIZE == __kernel_io_end which is 0
>>> when early_ioremap_setup() is called. __kernel_io_end is initialized
>>> little bit later in early_init_mmu().
>>>
>>> This fixes the initialization by swapping early_ioremap_setup and
>>> early_init_mmu.
>>
>> Hum ... Chris tested it on a T2080RDB, that must be a book3e.
>>
>> So we missed it. I guess your fix is right.
> 
> 
> Oh cool.

I forgot, your patch should include Fixes: tags.

Fixes: 265c3491c4bc ("powerpc: Add support for GENERIC_EARLY_IOREMAP")

If you still change the FIXADDR_SIZE, then it must also have:

Fixes: 9ccba66d4d2a ("powerpc/64: Fix the definition of the fixmap area")

> 
>>>
>>> This also fixes IOREMAP_END to use FIXADDR_SIZE defined just next to it,
>>> seems to make sense, unless there is some weird logic with redefining
>>> FIXADDR_SIZE as the compiling goes.
>>
>> Well, I don't think the order of defines matters, the change should be kept out of the fix.
> 
> When I see this:
> 
> #define IOREMAP_END    (KERN_IO_END - FIXADDR_SIZE)
> #define FIXADDR_SIZE    SZ_32M
> 
> 
> ... I have to think harder what FIXADDR_SIZE was in the first macro and in what order the 
> preprocessor expands them.
> 
> 
>> But if you want it anyway, then I'd suggest to move it before IOREMAP_BASE in order to keep the 3 
>> IOREMAP_xxx together.
> 
> Up to Michael, I guess.
> 
> 
>>
>>>
>>> Signed-off-by: Alexey Kardashevskiy <aik at ozlabs.ru>
>>
>> Reviewed-by: Christophe Leroy <christophe.leroy at csgroup.eu>
>>
>>> ---
>>>   arch/powerpc/include/asm/book3s/64/pgtable.h | 2 +-
>>>   arch/powerpc/kernel/setup_64.c               | 3 ++-
>>>   2 files changed, 3 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/arch/powerpc/include/asm/book3s/64/pgtable.h 
>>> b/arch/powerpc/include/asm/book3s/64/pgtable.h
>>> index a666d561b44d..54a06129794b 100644
>>> --- a/arch/powerpc/include/asm/book3s/64/pgtable.h
>>> +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h
>>> @@ -325,8 +325,8 @@ extern unsigned long pci_io_base;
>>>   #define  PHB_IO_END    (KERN_IO_START + FULL_IO_SIZE)
>>>   #define IOREMAP_BASE    (PHB_IO_END)
>>>   #define IOREMAP_START    (ioremap_bot)
>>> -#define IOREMAP_END    (KERN_IO_END - FIXADDR_SIZE)
>>>   #define FIXADDR_SIZE    SZ_32M
>>> +#define IOREMAP_END    (KERN_IO_END - FIXADDR_SIZE)
>>>   /* Advertise special mapping type for AGP */
>>>   #define HAVE_PAGE_AGP
>>> diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
>>> index b779d25761cf..ce09fe5debf4 100644
>>> --- a/arch/powerpc/kernel/setup_64.c
>>> +++ b/arch/powerpc/kernel/setup_64.c
>>> @@ -369,11 +369,12 @@ void __init early_setup(unsigned long dt_ptr)
>>>       apply_feature_fixups();
>>>       setup_feature_keys();
>>> -    early_ioremap_setup();
>>>       /* Initialize the hash table or TLB handling */
>>>       early_init_mmu();
>>> +    early_ioremap_setup();
>>> +
>>>       /*
>>>        * After firmware and early platform setup code has set things up,
>>>        * we note the SPR values for configurable control/performance
>>>
>