board/olpc: document flashing the JFFS2 image

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

diff --git a/board/olpc/readme.txt b/board/olpc/readme.txt
index 2ed44011f7bef5d304d1655c903fa4f956cbab85..f1110c82cb5ca9f205bb3e3e87bd84e4fed4428c 100644 (file)
--- a/board/olpc/readme.txt
+++ b/board/olpc/readme.txt
@@ -9,10 +9,13 @@ Supported models
 
 * OLPC XO-1
   The original NS Geode based OLPC laptop, uses the x86 architecture.
+  Can be booted either from an internal MTD device formatted with JFFS2
+  or from a FAT or EXT4 partition on a SD card or a USB flash stick.
 
 * OLPC XO-7.5
   The ARM-based laptop. Needs a recent enough firmware to provide a good
-  enough flattened device tree to the kernel.
+  enough flattened device tree to the kernel. Can be from a FAT or EXT4
+  partition on a internal eMMC, a SD card or a USB flash stick.
 
 Configure and build
 ===================
@@ -59,20 +62,37 @@ to update the firmware:
   ok flash ext:\q4e00ja.rom   \ Flash the "q4e00ja.rom" from the SD card
   ok flash u:\q4e00ja.rom     \ Flash the "q4e00ja.rom" from USB stick
 
-Create the bootable media
-=========================
+Create the bootable SD card or USB flash stick
+==============================================
 
-When the build is finished, the resulting image file will be called
-"sdcard.img". It can be written directly to a SD-card or and USB flash stick.
+When the build is finished, an image file called "sdcard.img" will be created.
+It is suitable for writing directly to a SD card, USB flash stick or (on a
+XO-1.75) the internal eMMC flash.
 
-Please double check that you're using the right device (e.g. with "lsblk"
-command). Doing the following will DESTROY ALL DATA that's currently on the
-media.
+Before writing the image, please double check that you're using the right
+device (e.g. with "lsblk" command). Doing the following will DESTROY ALL DATA
+that's currently on the media.
 
   # cat output/images/sdcard.img >/dev/<device>
 
+Flashing the JFFS2 image (XO-1 only)
+====================================
+
+Unlike XO-1.75, the internal NAND flash on XO-1 is accessed without a
+FTL and needs a flash-friendly filesystem. A build configured for XO-1
+creates a file named "root.jffs2" that can be written to it.
+
+One way to write it is from the Open Firmware prompt. First, partition
+and format a USB flash disk with a FAT file system and place the
+"root.jffs2" file onto it. Then power on the machine, enter the
+Open Firmware port by pressing the ESC key and run the following:
+
+  ok patch noop ?open-crcs copy-nand  \ Disable CRC check
+  ok copy-nand u:\root.jffs2
+
 Booting the machine
 ===================
 
 Once your machine is unlocked, it will automatically boot from your media
-wherever it will detect it attached to the USB bus or the SD card slot.
+wherever it will detect it attached to the USB bus or the SD card slot,
+otherwise it will proceed booting from the internal flash.