ARC: mm: document system mem map clearly

#endif /* !__ASSEMBLY__ */

/* Kernels Virtual memory area.

 * Unlike other architectures(MIPS, sh, cris ) ARC 700 does not have a

 * "kernel translated" region (like KSEG2 in MIPS). So we use a upper part

 * of the translated bottom 2GB for kernel virtual memory and protect

 * these pages from user accesses by disabling Ru, Eu and Wu.

/*

 * System Memory Map on ARC

 *

 * ---------------------------- (lower 2G, Translated) -------------------------

 * 0x0000_0000		0x5FFF_FFFF	(user vaddr: TASK_SIZE)

 * 0x6000_0000		0x6FFF_FFFF	(reserved gutter between U/K)

 * 0x7000_0000		0x7FFF_FFFF	(kvaddr: vmalloc/modules/pkmap..)

 *

 * PAGE_OFFSET ---------------- (Upper 2G, Untranslated) -----------------------

 * 0x8000_0000		0xBFFF_FFFF	(kernel direct mapped)

 * 0xC000_0000		0xFFFF_FFFF	(peripheral uncached space)

 * -----------------------------------------------------------------------------

 */

#define VMALLOC_SIZE	(0x10000000)	/* 256M */

#define VMALLOC_START	(PAGE_OFFSET - VMALLOC_SIZE)

#define VMALLOC_END	(PAGE_OFFSET)

#define VMALLOC_START	0x70000000

#define VMALLOC_SIZE	(PAGE_OFFSET - VMALLOC_START)

#define VMALLOC_END	(VMALLOC_START + VMALLOC_SIZE)

/* Most of the architectures seem to be keeping some kind of padding between

 * userspace TASK_SIZE and PAGE_OFFSET. i.e TASK_SIZE != PAGE_OFFSET.

 */

#define USER_KERNEL_GUTTER    0x10000000

/* User address space:

 * On ARC700, CPU allows the entire lower half of 32 bit address space to be

 * translated. Thus potentially 2G (0:0x7FFF_FFFF) could be User vaddr space.

 * However we steal 256M for kernel addr (0x7000_0000:0x7FFF_FFFF) and another

 * 256M (0x6000_0000:0x6FFF_FFFF) is gutter between user/kernel spaces

 * Thus total User vaddr space is (0:0x5FFF_FFFF)

 */

#define TASK_SIZE	(PAGE_OFFSET - VMALLOC_SIZE - USER_KERNEL_GUTTER)

#define TASK_SIZE	(VMALLOC_START - USER_KERNEL_GUTTER)

#define STACK_TOP       TASK_SIZE

#define STACK_TOP_MAX   STACK_TOP