ARM: implement debug_ll_io_init()

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@calxeda.com>
[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@nvidia.com>
Signed-off-by: Olof Johansson <olof@lixom.net>

3 files changed, 37 insertions, 0 deletions

diff --git a/arch/arm/include/asm/mach/map.h b/arch/arm/include/asm/mach/map.h
index 195ac2f9d3d3..2fe141fcc8d6 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 66f711b2e0e8..6809200c31fb 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 +126,11 @@ ENTRY(printch)
                 mov     pc, lr
 ENDPROC(printch)
 
+ENTRY(debug_ll_addr)
+                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 941dfb9e9a78..39719bb93caa 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);