ARC: mm: document system mem map clearly

Signed-off-by: NVineet Gupta <vgupta@synopsys.com>

arch/arc/include/asm/processor.h

@@ -100,29 +100,26 @@ extern unsigned int get_wchan(struct task_struct *p);
 
 #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

arch/arc/include/uapi/asm/page.h

@@ -30,7 +30,7 @@
 #define PAGE_OFFSET	(0x80000000)
 #else
 #define PAGE_SIZE	(1UL << PAGE_SHIFT)	/* Default 8K */
-#define PAGE_OFFSET	(0x80000000UL)	/* Kernel starts at 2G onwards */
+#define PAGE_OFFSET	(0x80000000UL)		/* Kernel starts at 2G onwards */
 #endif
 
 #define PAGE_MASK	(~(PAGE_SIZE-1))