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qi-update-README.patch

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Signed-off-by: Andy Green <andy@openmoko.com>
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Andy Green 2008-11-28 10:16:45 +00:00 committed by Andy Green
parent 12828f98f2
commit 4a503bbc81
1 changed files with 32 additions and 18 deletions
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qiboot/README
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@ -54,18 +54,30 @@ Booting Heuristics
Qi has one or more ways to fetch a kernel depending on the device it finds it is
running on, for example on GTA02 it can use NAND and SD card devices. It goes
through these device-specific storage devices in order and tries to boot the
first viable kernel it finds, usually /boot/uImage.bin.
first viable kernel it finds, usually /boot/uImage-device>.bin for example
/boot/uImage-GTA02.bin.
The kernel commandline used is associated with the storage device, this allows
the correct root= line to be arrived at without any work. The inability to set
the Qi kernel commandline externally is deliberate, two otherwise identical
devices differing by the kernel commandline or other "environment" is not good.
A whole class of bugs and support issues around private bootloader state are
therefore avoided.
You can disable a rootfs for consideration for boot if you add a file
/boot/noboot-<device>, eg, /boot/noboot-GTA02.
The kernel commandline used is associated with the storage device and partition,
this allows the correct root= line to be arrived at without any work.
If no kernel image can be found, Qi falls back to doing a memory test.
Appending to commandline
========================
You can append to the Qi commandline by creating a file /boot/append-<device>,
eg, /boot/append-GTA02 containing the additional kernel commandline you want.
This means you can affect the boot per-rootfs, but that if you reimage the
rootfs you at the same time define what is appeneded. Because these files are
looked for with the <device> name in them, options can be selected depending on
the device the rootfs is run on.
Initrd support
==============
@ -76,22 +88,24 @@ memory address in addition to kernel image. The ATAGs are issued accordingly.
Functional Differences from U-Boot on GTA02
===========================================
- Backlight is not enabled until Linux starts after a few seconds
- kernel loglevel is set to NOT output gobs of text to the screen
- On GTA02 will ALWAYS boot from uSD if first partition is ext2 and contains
/boot/uImage.bin, otherwise boots from NAND
- On GTA03 will ALWAYS boot from uSD second partition if /boot/uImage.bin is
present otherwise try the third / backup partition
- Backlight and USB is not enabled until Linux starts after a few seconds
- No startup splash screen
- by default there is no boot spew on the LCM
- On GTAxx boots from first uSD ext2 / 3 partition containing
/boot/uImage-<devicename>.bin present, eg, /boot/uImage-GTA02.bin, it checks
first three partitions in turn
- On GTA01 and 02 if nothing is workable on the SD Card, or it is not present,
Qi will try to boot from NAND
- You can disable a partition for boot by creating /boot/noboot-<devicename>,
eg, /boot/noboot-GTA02, it will skip it and check the next partition
- Way faster
- There is no concept of "staying in the bootloader". The bootloader exits to
Linux as fast as possible, that's all it does.
- USB is not started until Linux starts around 5 seconds after boot, there is
no DFU.