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

[Christophe Leroy]

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.

> 
> 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.
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.

> 
> 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
>