doc/README: documents and readme for NDS32 arch

Documents and READMEs for NDS32 architecture.
It patch also provides usage of SoC AG101 and board ADP-AG101.

Signed-off-by: Macpaul Lin <macpaul@andestech.com>

README

@@ -183,6 +183,10 @@ Directory Hierarchy:
       /mips32		Files specific to MIPS32 CPUs
       /xburst		Files specific to Ingenic XBurst CPUs
     /lib		Architecture specific library files
+  /nds32		Files generic to NDS32 architecture
+    /cpu		CPU specific files
+      /n1213		Files specific to Andes Technology N1213 CPUs
+    /lib		Architecture specific library files
   /nios2		Files generic to Altera NIOS2 architecture
     /cpu		CPU specific files
     /lib		Architecture specific library files
@@ -3156,7 +3160,7 @@ Low Level (hardware related) configuration options:
 		globally (CONFIG_CMD_MEM).
 
 - CONFIG_SKIP_LOWLEVEL_INIT
-		[ARM, MIPS only] If this variable is defined, then certain
+		[ARM, NDS32, MIPS only] If this variable is defined, then certain
 		low level initializations (like setting up the memory
 		controller) are omitted and/or U-Boot does not
 		relocate itself into RAM.
@@ -3723,8 +3727,8 @@ details; basically, the header defines the following image properties:
   Currently supported: Linux, NetBSD, VxWorks, QNX, RTEMS, LynxOS,
   INTEGRITY).
 * Target CPU Architecture (Provisions for Alpha, ARM, AVR32, Intel x86,
-  IA64, MIPS, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
-  Currently supported: ARM, AVR32, Intel x86, MIPS, Nios II, PowerPC).
+  IA64, MIPS, NDS32, Nios II, PowerPC, IBM S390, SuperH, Sparc, Sparc 64 Bit;
+  Currently supported: ARM, AVR32, Intel x86, MIPS, NDS32, Nios II, PowerPC).
 * Compression Type (uncompressed, gzip, bzip2)
 * Load Address
 * Entry Point
@@ -4417,6 +4421,20 @@ On Nios II, the ABI is documented here:
     Note: on Nios II, we give "-G0" option to gcc and don't use gp
     to access small data sections, so gp is free.
 
+On NDS32, the following registers are used:
+
+	R0-R1:	argument/return
+	R2-R5:	argument
+	R15:	temporary register for assembler
+	R16:	trampoline register
+	R28:	frame pointer (FP)
+	R29:	global pointer (GP)
+	R30:	link register (LP)
+	R31:	stack pointer (SP)
+	PC:	program counter (PC)
+
+    ==> U-Boot will use R10 to hold a pointer to the global data
+
 NOTE: DECLARE_GLOBAL_DATA_PTR must be used with file-global scope,
 or current versions of GCC may "optimize" the code too much.
 

doc/README.N1213

@@ -0,0 +1,55 @@
+N1213 is a configurable hard/soft core of NDS32's N12 CPU family.
+
+Features
+========
+
+CPU Core
+ - 16-/32-bit mixable instruction format.
+ - 32 general-purpose 32-bit registers.
+ - 8-stage pipeline.
+ - Dynamic branch prediction.
+ - 32/64/128/256 BTB.
+ - Return address stack (RAS).
+ - Vector interrupts for internal/external.
+   interrupt controller with 6 hardware interrupt signals.
+ - 3 HW-level nested interruptions.
+ - User and super-user mode support.
+ - Memory-mapped I/O.
+ - Address space up to 4GB.
+
+Memory Management Unit
+ - TLB
+   - 4/8-entry fully associative iTLB/dTLB.
+   - 32/64/128-entry 4-way set-associati.ve main TLB.
+   - TLB locking support
+ - Optional hardware page table walker.
+ - Two groups of page size support.
+  - 4KB & 1MB.
+  - 8KB & 1MB.
+
+Memory Subsystem
+ - I & D cache.
+   - Virtually indexed and physically tagged.
+   - Cache size: 8KB/16KB/32KB/64KB.
+   - Cache line size: 16B/32B.
+   - Set associativity: 2-way, 4-way or direct-mapped.
+   - Cache locking support.
+ - I & D local memory (LM).
+   - Size: 4KB to 1MB.
+   - Bank numbers: 1 or 2.
+   - Optional 1D/2D DMA engine.
+   - Internal or external to CPU core.
+
+Bus Interface
+ - Synchronous/Asynchronous AHB bus: 0, 1 or 2 ports.
+ - Synchronous High speed memory port.
+   (HSMP): 0, 1 or 2 ports.
+
+Debug
+ - JTAG debug interface.
+ - Embedded debug module (EDM).
+ - Optional embedded program tracer interface.
+
+Miscellaneous
+ - Programmable data endian control.
+ - Performance monitoring mechanism.

doc/README.NDS32

@@ -0,0 +1,41 @@
+NDS32 is a new high-performance 32-bit RISC microprocessor core.
+
+http://www.andestech.com/
+
+AndeStar ISA
+============
+AndeStar is a patent-pending 16-bit/32-bit mixed-length instruction set to
+achieve optimal system performance, code density, and power efficiency.
+
+It contains the following features:
+ - Intermixable 32-bit and 16-bit instruction sets without the need for
+   mode switch.
+ - 16-bit instructions as a frequently used subset of 32-bit instructions.
+ - RISC-style register-based instruction set.
+ - 32 32-bit General Purpose Registers (GPR).
+ - Upto 1024 User Special Registers (USR) for existing and extension
+   instructions.
+ - Rich load/store instructions for...
+   - Single memory access with base address update.
+   - Multiple aligned and unaligned memory accesses for memory copy and stack
+     operations.
+   - Data prefetch to improve data cache performance.
+   - Non-bus locking synchronization instructions.
+ - PC relative jump and PC read instructions for efficient position independent
+   code.
+ - Multiply-add and multiple-sub with 64-bit accumulator.
+ - Instruction for efficient power management.
+ - Bi-endian support.
+ - Three instruction extension space for application acceleration:
+   - Performance extension.
+   - Andes future extensions (for floating-point, multimedia, etc.)
+   - Customer extensions.
+
+AndesCore CPU
+=============
+Andes Technology has 4 families of CPU cores: N12, N10, N9, N8.
+
+For details about N12 CPU family, please check doc/README.N1213.
+
+The NDS32 ports of u-boot, the Linux kernel, the GNU toolchain and
+other associated software are actively supported by Andes Technology Corporation.

doc/README.ag101

@@ -0,0 +1,74 @@
+Andes Technology SoC AG101
+==========================
+
+AG101 is the first SoC produced by Andes Technology using N1213 CPU core.
+AG101 has integrated both AHB and APB bus and many periphals for application
+and product development.
+
+ADP-AG101
+=========
+
+ADP-AG101 is the SoC with AG101 hardcore CPU.
+
+Please check http://www.andestech.com/p2-4.htm for detail of this SoC.
+
+Configurations
+==============
+
+CONFIG_MEM_REMAP:
+	Doing memory remap is essential for preparing some non-OS or RTOS
+	applications.
+
+	This is also a must on ADP-AG101 board.
+	(While other boards may not have this problem).
+
+	The reason is because the ROM/FLASH circuit on PCB board.
+	AG101-A0 board has 2 jumpers MA17 and SW5 to configure which
+	ROM/FLASH is used to boot.
+
+	When SW5 = "0101", MA17 = LO, the ROM is connected to BANK0,
+	and the FLASH is connected to BANK1.
+	When SW5 = "1010", MA17 = HI, the ROM is disabled (still at BANK0),
+	and the FLASH is connected to BANK0.
+	It will occur problem when doing flash probing if the flash is at
+	BANK0 (0x00000000) while memory remapping was skipped.
+
+	Other board like ADP-AG101P may not enable this since there is only
+	a FLASH connected to bank0.
+
+CONFIG_SKIP_LOWLEVEL_INIT:
+	If you want to boot this system from FLASH and bypass e-bios (the
+	other boot loader on ROM). You should undefine CONFIG_SKIP_LOWLEVEL_INIT
+	in "include/configs/adp-ag101.h".
+
+Build and boot steps
+====================
+
+build:
+1. Prepare the toolchains and make sure the $PATH to toolchains is correct.
+2. Use `make adp-ag101` in u-boot root to build the image.
+
+burn u-boot to flash:
+1. Make sure the MA17 (J16) is Lo.
+2. Make sure the dip switch SW5 is set to "0101".
+3. Power On. Press button "S1", then press button "SW1", then you will found the
+   debug LED show 67 means the system successfully booted into e-bios.
+   Now you can control the e-bios boot loader from your console.
+4. Under "Command>>" prompt, enter "97" (CopyImageFromCard)
+5. Under "Type Dir Name of [CF/SD] =>" promtp, enter "c".
+6. Under "Enter Filename =>" prompt, enter the file name of u-boot image you
+   just build. It is usually "u-boot.bin".
+7. Under "Enter Dest. Address =>" prompt, enter the memory address where you
+   want to put the binary from SD card to RAM.
+   Address "0x500000" is our suggestion.
+8. Under "Command>>" prompt again, enter "55" (CLI) to use interactive command
+   environment.
+9. Under "CLI>" prompt, enter "burn 0x500000 0x80400000 0x30000" to burn the
+   binary from RAM to FLASH.
+10. Under "CLI>" prompt, enter "exit" to finish the burn process.
+
+boot u-boot from flash:
+1. Make sure the MA17 (J16) is Hi).
+2. Make sure the dip switch SW5 is set to "1010".
+3. Power On. Press button "S1", then you will see the debug LED count to 20.
+4. Now you can use u-boot on ADP-AG101 board.

doc/README.standalone

@@ -56,6 +56,7 @@ Design Notes on Exporting U-Boot Functions to Standalone Applications:
 	ARM		0x0c100000	0x0c100000
 	MIPS		0x80200000	0x80200000
 	Blackfin	0x00001000	0x00001000
+	NDS32		0x00300000	0x00300000
 	Nios II		0x02000000	0x02000000
 
    For example, the "hello world" application may be loaded and