Re: ioremap() fail on physical address 0x0 in 3.4 kernel

[Murali Nalajala <mnalajal@codeaurora.org>]

On 8/22/2012 3:23 PM, Russell King - ARM Linux wrote:
> On Wed, Aug 22, 2012 at 12:16:08PM +0530, Trilok Soni wrote:
>> Thanks for the patch, but how about just checking pmd_none on such
>> addresses and since there won't be any mapping created for such gaps? We
>> need to check if this is fine for all, since I remember that Nico
>> added these functions for the OMAP boot issue I guess.
>
> A better solution would be as below - this requires no changes to the
> existing ioremap code, we just mark these differently.
>
> diff --git a/arch/arm/mm/mm.h b/arch/arm/mm/mm.h
> index 2e8a1ef..87fa3f2 100644
> --- a/arch/arm/mm/mm.h
> +++ b/arch/arm/mm/mm.h
> @@ -55,6 +55,9 @@ extern void __flush_dcache_page(struct address_space *mapping, struct page *page
>   /* permanent static mappings from iotable_init() */
>   #define VM_ARM_STATIC_MAPPING	0x40000000
>
> +/* empty mapping */
> +#define VM_ARM_EMPTY_MAPPING	0x20000000
> +
>   /* mapping type (attributes) for permanent static mappings */
>   #define VM_ARM_MTYPE(mt)		((mt)<<  20)
>   #define VM_ARM_MTYPE_MASK	(0x1f<<  20)
> diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
> index cf4528d..da90ef1 100644
> --- a/arch/arm/mm/mmu.c
> +++ b/arch/arm/mm/mmu.c
> @@ -813,7 +813,7 @@ static void __init pmd_empty_section_gap(unsigned long addr)
>   	vm = early_alloc_aligned(sizeof(*vm), __alignof__(*vm));
>   	vm->addr = (void *)addr;
>   	vm->size = SECTION_SIZE;
> -	vm->flags = VM_IOREMAP | VM_ARM_STATIC_MAPPING;
> +	vm->flags = VM_IOREMAP | VM_ARM_EMPTY_MAPPING;
>   	vm->caller = pmd_empty_section_gap;
>   	vm_area_add_early(vm);
>   }
> @@ -826,7 +826,7 @@ static void __init fill_pmd_gaps(void)
>
>   	/* we're still single threaded hence no lock needed here */
>   	for (vm = vmlist; vm; vm = vm->next) {
> -		if (!(vm->flags&  VM_ARM_STATIC_MAPPING))
> +		if (!(vm->flags&  (VM_ARM_STATIC_MAPPING | VM_ARM_EMPTY_MAPPING))
>   			continue;
>   		addr = (unsigned long)vm->addr;
>   		if (addr<  next)
>
Tested on MSM platform

Tested-by: Murali Nalajala <mnalajal@codeaurora.org>

Thanks,
Murali N

-- 
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