[U-Boot] [PATCH] nios2: add README.nios2

[Thomas Chou]

Add README.nios2 about how to add nios2 boards to u-boot.

Signed-off-by: Thomas Chou <thomas at wytron.com.tw>
---
 doc/README.nios2 | 86 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 86 insertions(+)
 create mode 100644 doc/README.nios2

diff --git a/doc/README.nios2 b/doc/README.nios2
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+Nios II is a 32-bit embedded-processor architecture designed 
+specifically for the Altera family of FPGAs. 
+
+Please refer to the link for more information on Nios II, 
+https://www.altera.com/products/processors/overview.html
+
+Please refer to the link for Linux port and toolchains,
+http://rocketboards.org/foswiki/view/Documentation/NiosIILinuxUserManual
+
+The Nios II port of u-boot is controlled by device tree. To add a new 
+board/configuration (eg, mysystem) to u-boot, you will need three files.
+
+1. The device tree source which descibe the hardware, dts file.
+    arch/nios2/dts/mysystem.dts
+
+2. Default configuration of Kconfig, defconfig file.
+    configs/mysystem_defconfig
+
+3. The legacy board header file.
+    include/configs/mysystem.h
+
+The device tree source must be generated from your qsys/sopc design file 
+using the sopc2dts tool. Then modified to fit your configuration. Please 
+find the sopc2dts download and usage at the wiki,
+http://www.alterawiki.com/wiki/Sopc2dts
+
+java -jar sopc2dts.jar --force-altr -i mysystem.sopcinfo -o mysystem.dts
+
+You will need to add additional properties to the dts. Please find an 
+example at, arch/nios2/dts/3c120_devboard.dts.
+
+1. Add "u-boot,dm-pre-reloc" property to the cpu and the serial node 
+which you will use for console.
+
+2. Add "stdout-path=..." property with your serial path to the chosen 
+node.
+
+Next, you will need a default config file. You may start with 
+nios2-generic_defconfig, modify the options and save it.
+
+make nios2-generic_defconfig
+make menuconfig
+make savedefconfig
+cp defconfig configs/mysystem_defconfig
+
+You will need to change the names of board header file and device tree, 
+and select the drivers.
+
+Nios II architecture  --->
+  (mysystem) Board header file
+Device Tree Control  --->
+  (mysystem) Default Device Tree for DT control
+
+There is a selection of "Provider of DTB for DT control" in the Device 
+Tree Control menu.
+
+( ) Separate DTB for DT control, will cat the dtb to end of u-boot 
+binary, output u-boot-dtb.bin. This should be used for production.
+If you use boot copier, like epcs boot copier, make sure the copier 
+copies all the u-boot-dtb.bin, not just u-boot.bin.
+
+( ) Embedded DTB for DT control, will include the dtb inside the u-boot 
+binary. This is handy for development, eg, using gdb or nios2-download.
+
+The last thing, legacy board header file describes those config options 
+not covered in Kconfig yet. You may copy it from nios2-generic.h.
+
+cp include/configs/nios2-generic.h include/configs/mysystem.h
+
+Please change the sdram base and size to your board. The base should be 
+cached virtual address, for nios2 with mmu it is 0xCxxx-xxxx to 
+0xDxxx-xxxx.
+
+#define CONFIG_SYS_SDRAM_BASE		0xD0000000
+#define CONFIG_SYS_SDRAM_SIZE		0x08000000
+
+You will need to change the environment variables location and setting, 
+too. You may change other configs to fit your board.
+
+After all these changes, you may build and test.
+
+export CROSS_COMPILE=nios2-elf-  (or nios2-linux-gnu-)
+make mysystem_defconfig
+make
+
+Enjoy!
-- 
2.1.4