Am 09.06.2015 um 15:56 schrieb Paul Boddie <p...@boddie.org.uk>: > On Tuesday 9. June 2015 14.55.48 Dr. H. Nikolaus Schaller wrote: >> >> Am 09.06.2015 um 13:45 schrieb Paul Boddie <p...@boddie.org.uk>: >>> >>> https://www.mail-archive.com/mipsbook-devel%40linuxtogo.org/msg00181.html >> >> Indeed! Thanks for looking it up. > > [...] > >> Fortunately, I have found copies of PC701-LX-u-boot-1.1.6.tar.bz2 on my >> daily work machine… >> >> So it is not lost. I have uploaded it to >> >> http://download.goldelico.com/letux-400/files/ > > I imagine that it will be mostly the same as the repositories I found... > >>> Fortunately, I found the following repository containing U-Boot with >>> jz4730 support: >>> >>> https://github.com/shenhaocn/jzcode-x11 >>> >>> There's also a specific U-Boot repository, but I can't see any notable >>> differences between it and the other one: >>> >>> https://github.com/shenhaocn/jz-uboot >>> >>> I'm sure I've seen boot code before, but I think it's the code in the 2.6 >>> kernel that detects various keys and supposedly performs NAND-flashing >>> operations. >> >> Yes, according to my 5 years old description there are multiple locations >> where hot keys are detected to help the boot process. A big hack… No chance >> to get it upstream to kernel.org or denx :) > > I seem to remember a bit more of this now: before the init process is run, > the > user has the chance to hold down a key, and then the relevant resources are > accessed: > > http://projects.goldelico.com/p/letux-400/source/tree/master/arch/mips/jz4730/board- > minipc.c#L126 > > http://projects.goldelico.com/p/letux-400/source/tree/master/init/do_mounts.c#L425 > > This seems to allow an alternative root filesystem, at least. > >> The key point is that U-Boot can only boot from NAND or SD/MMC. And it >> can boot the “minifs” which is a stripped down Linux with running a single >> shell script in busybox. That script provides some user interface - and of >> course USB drivers (and network) to load recovery systems from. > > It might be interesting to get some low-level bootloader to work from SD/MMC > if possible (that is, if possible on the Letux, not if generally possible for > U-Boot). I'm naturally wary of using the NAND, anyway, and I do use the > NanoNote with a microSD/MMC card instead of booting from NAND if I don't need > to use the MMC port for homebrew hardware.
It could be possible to load another instance of U-Boot instead of a kernel. And then do the final work. Or modify the minifs. > >> I have found that we had written a simple replacement minifs (which is not >> the same as the one that comes shipped with the hardware). But if you >> did not touch the original, it should be possible to read out the NAND >> partition. >> >> http://projects.goldelico.com/p/l400-rootfs/source/tree/master/config/root/ >> mkminifs >> http://projects.goldelico.com/p/l400-rootfs/source/tree/master/config/root >> /recover > > I'll have to take a look at that. > >>> It becomes difficult to track all the different resources, >>> especially when some of them tend to go away and not always come back, >>> like all the kwaak.net ones which even the Internet Archive doesn’t have >>> any more. >> >> This is why http://projects.goldelico.com/p/letux-400/ and siblings like >> http://projects.goldelico.com/p/l400-rootfs/ exist. My target is that this >> resource is never going away (at least as long as the company exists and >> can pay for the server operation :). >> >> Anyways, I also plan to consolidate the GTA04 boot/kernel/rootfs system >> with the Letux400 boot/kernel/rootfs as soon as we have MIPS/JZ device >> tree support in the kernel. Then, this u-boot will also be unpacked into >> git (and mirrored to github). > > Right. At this point, I'm not actively pursuing the Linux kernel stuff as I > don't think I can muddle my way through the necessary work. Moreover, I got > the impression that other people need to finish off their own efforts around > device tree and the necessary changes around it before we even have a chance > of getting the jz4730 stuff to work with it. IMHO progress is promising. But it is still not arrived at linux-next so chances for 4.2-rc1 are not very high. > >> If someone needs write access to this project forge to update information, >> please register and let me know. > > I'll think about doing that. > >>> Ultimately, for the Letux (but also for less awkward NanoNote >>> experiments) it may be worthwhile focusing on a payload loaded from >>> SD/MMC media, however. >> >> For the initial work, I think we should indeed focus on SD/MMC. And only if >> it becomes more stable, complete boot from USB can be revisited. > > I did wonder whether it was even possible without opening up the Letux unit > itself, and whether it would be possible even then. The NanoNote deliberately > exposes a contact in the battery compartment for the hardware USB boot mode, > meaning that even if U-Boot is broken or doesn't support the software USB > boot > mode (which appears to involve some initialisation of the SoC's bootloader, > or > maybe even a partial reimplementation of it), it's still possible to activate > the hardware mode. If you open the L400 it is possible to solder an RS232 adapter for console access. And it has a flex cable connector for JTAG. > > Another thing that I'm not clear about (without studying the schematic) is > how > the USB port on the Letux is connected to the SoC and whether it would make > sense to use the provided USB ports for booting purposes. The NanoNote is > only > capable of being a USB peripheral, whereas the Letux is presumably meant to > be > a USB host, although I guess it can also be a peripheral. Either way, the > internal “wiring" would need to be right for any boot mode to be exposed. It appears that the jz4730 has two USB1 host mode only ports (DPLS0/DNS0, DPLS1/DMNS1). One goes directly to one of the 3 usb sockets while the other goes to a 4 port-hub AU9254A21. One of the 4 ports is unused, two are the other two USB sockets and the last one goes to an CSC0101A-S16 PS2 converter (touch pad). The JZ4730 also has a PS2 interface but that ends in test points… None of the USB sockets has an ID pin - so they are not OTG capable. In summary: the L400 can only be USB host and not USB peripheral. > > But yes, employing SD/MMC would be best, and maybe I should investigate that > on the NanoNote, booting into my own test payload directly from U-Boot. And > it > would be interesting to know if a bootloader could be deployed on SD/MMC for > the Letux. Currently, I see the limitation being that the 2.6 kernel hacks > only support changing the root filesystem to the MMC storage, not invoking a > completely new payload from it. Yes, because it is probably a little risky to do so. BR, NIkolaus _______________________________________________ Mipsbook-devel mailing list Mipsbook-devel@linuxtogo.org http://lists.linuxtogo.org/cgi-bin/mailman/listinfo/mipsbook-devel
