ARM: implement debug_ll_io_init()

From: Rob Herring <[email protected]>

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.

[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.]

---
Arnd, Olof, could this patch be placed into a standalone topic branch in arm-soc branch; I'd like to make use of this patch for both Tegra and bcm2835 this cycle, and perhaps others might too. Thanks.

v4: Fix DEBUG_SEMIHOSTING's debug_ll_addr to actually fill in the "out"
parameters.
v3: New patch.

---
 arch/arm/include/asm/mach/map.h |    7 +++++++
 arch/arm/kernel/debug.S         |   14 ++++++++++++++
 arch/arm/mm/mmu.c               |   16 ++++++++++++++++
 3 files changed, 37 insertions(+), 0 deletions(-)

index 195ac2f..2fe141f 100644
@@ -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);
 /*

index 66f711b..6809200 100644
@@ -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

index b675918..08d04fc 100644
@@ -893,6 +893,22 @@ 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);
 

1.7.0.4

Done, applied to single-patch branch devel/debug_ll_init. I'll bring that in at next/multiplatform as well.

-Olof

Thanks very much. I've merged this into the Tegra tree.