powerpc: gamecube/wii: early debugging using usbgecko

Add support for using the USB Gecko adapter as an early debugging
console on the Nintendo GameCube and Wii video game consoles.
The USB Gecko is a 3rd party memory card interface adapter that provides
a EXI (External Interface) to USB serial converter.
Signed-off-by: NAlbert Herranz <albert_herranz@yahoo.es>
Acked-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>

arch/powerpc/Kconfig.debug

@@ -254,6 +254,14 @@ config PPC_EARLY_DEBUG_CPM
 	  using a CPM-based serial port.  This assumes that the bootwrapper
 	  has run, and set up the CPM in a particular way.
 
+config PPC_EARLY_DEBUG_USBGECKO
+	bool "Early debugging through the USB Gecko adapter"
+	depends on GAMECUBE_COMMON
+	select USBGECKO_UDBG
+	help
+	  Select this to enable early debugging for Nintendo GameCube/Wii
+	  consoles via an external USB Gecko adapter.
+
 endchoice
 
 config PPC_EARLY_DEBUG_44x_PHYSLOW

arch/powerpc/include/asm/udbg.h

@@ -51,6 +51,7 @@ extern void __init udbg_init_btext(void);
 extern void __init udbg_init_44x_as1(void);
 extern void __init udbg_init_40x_realmode(void);
 extern void __init udbg_init_cpm(void);
+extern void __init udbg_init_usbgecko(void);
 
 #endif /* __KERNEL__ */
 #endif /* _ASM_POWERPC_UDBG_H */

arch/powerpc/kernel/head_32.S

@@ -164,6 +164,9 @@ __after_mmu_off:
 #ifdef CONFIG_PPC_EARLY_DEBUG_CPM
 	bl	setup_cpm_bat
 #endif
+#ifdef CONFIG_PPC_EARLY_DEBUG_USBGECKO
+	bl	setup_usbgecko_bat
+#endif
 
 /*
  * Call setup_cpu for CPU 0 and initialize 6xx Idle
@@ -1203,6 +1206,28 @@ setup_cpm_bat:
 	blr
 #endif
 
+#ifdef CONFIG_PPC_EARLY_DEBUG_USBGECKO
+setup_usbgecko_bat:
+	/* prepare a BAT for early io */
+#if defined(CONFIG_GAMECUBE)
+	lis	r8, 0x0c00
+#elif defined(CONFIG_WII)
+	lis	r8, 0x0d00
+#else
+#error Invalid platform for USB Gecko based early debugging.
+#endif
+	/*
+	 * The virtual address used must match the virtual address
+	 * associated to the fixmap entry FIX_EARLY_DEBUG_BASE.
+	 */
+	lis	r11, 0xfffe	/* top 128K */
+	ori	r8, r8, 0x002a	/* uncached, guarded ,rw */
+	ori	r11, r11, 0x2	/* 128K, Vs=1, Vp=0 */
+	mtspr	SPRN_DBAT1L, r8
+	mtspr	SPRN_DBAT1U, r11
+	blr
+#endif
+
 #ifdef CONFIG_8260
 /* Jump into the system reset for the rom.
  * We first disable the MMU, and then jump to the ROM reset address.

arch/powerpc/kernel/udbg.c

@@ -60,6 +60,8 @@ void __init udbg_early_init(void)
 	udbg_init_40x_realmode();
 #elif defined(CONFIG_PPC_EARLY_DEBUG_CPM)
 	udbg_init_cpm();
+#elif defined(CONFIG_PPC_EARLY_DEBUG_USBGECKO)
+	udbg_init_usbgecko();
 #endif
 
 #ifdef CONFIG_PPC_EARLY_DEBUG

arch/powerpc/platforms/embedded6xx/usbgecko_udbg.c

@@ -17,6 +17,7 @@
 #include <asm/io.h>
 #include <asm/prom.h>
 #include <asm/udbg.h>
+#include <asm/fixmap.h>
 
 #include "usbgecko_udbg.h"
 
@@ -270,3 +271,58 @@ void __init ug_udbg_init(void)
 		of_node_put(np);
 	return;
 }
+
+#ifdef CONFIG_PPC_EARLY_DEBUG_USBGECKO
+
+static phys_addr_t __init ug_early_grab_io_addr(void)
+{
+#if defined(CONFIG_GAMECUBE)
+	return 0x0c000000;
+#elif defined(CONFIG_WII)
+	return 0x0d000000;
+#else
+#error Invalid platform for USB Gecko based early debugging.
+#endif
+}
+
+/*
+ * USB Gecko early debug support initialization for udbg.
+ */
+void __init udbg_init_usbgecko(void)
+{
+	void __iomem *early_debug_area;
+	void __iomem *exi_io_base;
+
+	/*
+	 * At this point we have a BAT already setup that enables I/O
+	 * to the EXI hardware.
+	 *
+	 * The BAT uses a virtual address range reserved at the fixmap.
+	 * This must match the virtual address configured in
+	 * head_32.S:setup_usbgecko_bat().
+	 */
+	early_debug_area = (void __iomem *)__fix_to_virt(FIX_EARLY_DEBUG_BASE);
+	exi_io_base = early_debug_area + 0x00006800;
+
+	/* try to detect a USB Gecko */
+	if (!ug_udbg_probe(exi_io_base))
+		return;
+
+	/* we found a USB Gecko, load udbg hooks */
+	udbg_putc = ug_udbg_putc;
+	udbg_getc = ug_udbg_getc;
+	udbg_getc_poll = ug_udbg_getc_poll;
+
+	/*
+	 * Prepare again the same BAT for MMU_init.
+	 * This allows udbg I/O to continue working after the MMU is
+	 * turned on for real.
+	 * It is safe to continue using the same virtual address as it is
+	 * a reserved fixmap area.
+	 */
+	setbat(1, (unsigned long)early_debug_area,
+	       ug_early_grab_io_addr(), 128*1024, PAGE_KERNEL_NCG);
+}
+
+#endif /* CONFIG_PPC_EARLY_DEBUG_USBGECKO */
+

arch/powerpc/platforms/embedded6xx/usbgecko_udbg.h

@@ -27,4 +27,6 @@ static inline void __init ug_udbg_init(void)
 
 #endif /* CONFIG_USBGECKO_UDBG */
 
+void __init udbg_init_usbgecko(void);
+
 #endif /* __USBGECKO_UDBG_H */