Re: [PATCH V3 1/5] ARM: implement debug_ll_io_init()

[Rob Herring <robherring2-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

On 10/19/2012 05:41 PM, Stephen Warren wrote:
> From: Rob Herring <robherring2-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> 
> When using DEBUG_LL, the UART's (or other HW's) registers are mapped
> into early page tables based on the results of assembly macro addruart.
> Later, when the page tables are replaced, the same virtual address must
> remain valid. Historically, this has been ensured by using defines from
> <mach/iomap.h> in both the implementation of addruart, and the machine's
> .map_io() function. However, with the move to single zImage, we wish to
> remove <mach/iomap.h>. To enable this, the macro addruart may be used
> when constructing the late page tables too; addruart is exposed as a
> C function debug_ll_addr(), and used to set up the required mapping in
> debug_ll_io_init(), which may called on an opt-in basis from a machine's
> .map_io() function.
> 
> Signed-off-by: Rob Herring <rob.herring-bsGFqQB8/DxBDgjK7y7TUQ@public.gmane.org>
> [swarren: Mask map.virtual with PAGE_MASK. Checked for NULL results from
>  debug_ll_addr (e.g. when selected UART isn't valid). Fixed compile when
>  either !CONFIG_DEBUG_LL or CONFIG_DEBUG_SEMIHOSTING.]
> Signed-off-by: Stephen Warren <swarren-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
> ---
> I assume this first patch should actually go into some arm-soc branch so
> that if others want to take advantage of it this kernel cycle, they can.
> 
> v3: New patch.
> ---
>  arch/arm/include/asm/mach/map.h |    7 +++++++
>  arch/arm/kernel/debug.S         |   13 +++++++++++++
>  arch/arm/mm/mmu.c               |   16 ++++++++++++++++
>  3 files changed, 36 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/arm/include/asm/mach/map.h b/arch/arm/include/asm/mach/map.h
> index 195ac2f..2fe141f 100644
> --- a/arch/arm/include/asm/mach/map.h
> +++ b/arch/arm/include/asm/mach/map.h
> @@ -40,6 +40,13 @@ extern void iotable_init(struct map_desc *, int);
>  extern void vm_reserve_area_early(unsigned long addr, unsigned long size,
>  				  void *caller);
>  
> +#ifdef CONFIG_DEBUG_LL
> +extern void debug_ll_addr(unsigned long *paddr, unsigned long *vaddr);
> +extern void debug_ll_io_init(void);
> +#else
> +static inline void debug_ll_io_init(void) {}
> +#endif
> +
>  struct mem_type;
>  extern const struct mem_type *get_mem_type(unsigned int type);
>  /*
> diff --git a/arch/arm/kernel/debug.S b/arch/arm/kernel/debug.S
> index 66f711b..7525ce4 100644
> --- a/arch/arm/kernel/debug.S
> +++ b/arch/arm/kernel/debug.S
> @@ -100,6 +100,13 @@ ENTRY(printch)
>  		b	1b
>  ENDPROC(printch)
>  
> +ENTRY(debug_ll_addr)
> +		addruart r2, r3, ip
> +		str	r2, [r0]
> +		str	r3, [r1]
> +		mov	pc, lr
> +ENDPROC(debug_ll_addr)
> +
>  #else
>  
>  ENTRY(printascii)
> @@ -119,4 +126,10 @@ ENTRY(printch)
>  		mov	pc, lr
>  ENDPROC(printch)
>  
> +ENTRY(debug_ll_addr)
> +		mov	r2, #0
> +		mov	r3, #0

Don't you want:

mov r2, #0
str r2, [r0]
str r2, [r1]

> +		mov	pc, lr
> +ENDPROC(debug_ll_addr)
> +
>  #endif
> diff --git a/arch/arm/mm/mmu.c b/arch/arm/mm/mmu.c
> index 941dfb9..39719bb 100644
> --- a/arch/arm/mm/mmu.c
> +++ b/arch/arm/mm/mmu.c
> @@ -876,6 +876,22 @@ static void __init pci_reserve_io(void)
>  #define pci_reserve_io() do { } while (0)
>  #endif
>  
> +#ifdef CONFIG_DEBUG_LL
> +void __init debug_ll_io_init(void)
> +{
> +	struct map_desc map;
> +
> +	debug_ll_addr(&map.pfn, &map.virtual);
> +	if (!map.pfn || !map.virtual)
> +		return;
> +	map.pfn = __phys_to_pfn(map.pfn);
> +	map.virtual &= PAGE_MASK;
> +	map.length = PAGE_SIZE;
> +	map.type = MT_DEVICE;
> +	create_mapping(&map);
> +}
> +#endif
> +
>  static void * __initdata vmalloc_min =
>  	(void *)(VMALLOC_END - (240 << 20) - VMALLOC_OFFSET);
>  
>