* Stephen Warren wrote: > On 04/26/2012 11:10 PM, Thierry Reding wrote: > > * Stephen Warren wrote: > >> On 04/26/2012 12:32 PM, Thierry Reding wrote: > >>> The problem is that neither the format of the BCT nor that of the PT is > >>> documented anywhere. It seems like the BCT contains a reference to where > >>> in > >>> the flash the PT starts but I wasn't able to find out where. > ... > >>> As I said before, the biggest problem with updating the whole content is > >>> that > >>> there's no documentation about either the BCT or the PT. There's > >>> cbootimage > >>> on gitorious that has some information about the BCT, but it's incomplete. > >> > >> Out of curiosity, what's missing from cbootimage? > > > > It's missing support for PT. That may not be necessary in a setup where we > > initialize the NAND from Linux user space, though, so maybe it would be > > enough. > > I don't believe the Tegra boot process actually /requires/ the PT even > exist. IIRC, the boot ROM searches for the BCT, and the BCT contains a > pointer to the bootloader (e.g. U-Boot), so it's only at a later stage > in the game that anything would care about the PT. As such, worrying > about the PT (or even including it) may be pointless.
After digging into this some more, I get the same impression. PT seems entirely optional. Information about the bootloader seems to be stored within the BCT. > I believe that TrimSlice's firmware recovery SD card images are created > solely using cbootimage, and hence most likely have no PT, although > obviously no additional partitions/file-systems on the media. It looks like cbootimage does have support for generating the bootloader bits, so maybe I can get this to work. > Perhaps you could define some hard-coded "MTD" partitions (e.g. the > first 1MB and the rest), where the first 1MB contains BCT + U-Boot and > the rest contains a regular MBR or GPT partition table. I /think/ there > may even be a kernel command-line option to define the MTD partition layout? > > Or, you could probably even get away with using a GPT for the entire > NAND by placing just the secondary GPT at the end of the NAND, putting > the BCT+U-Boot right at the start, and defining a GPT partition to > protect/cover BCT+U-Boot. I vaguely recall trying this on some Tegra > device, but I may be wrong. I didn't even know that you could put an MBR or GPT onto NAND. I was under the impression that the only way to partition flash was via MTD partitions. I'll have to see if I can make such a setup work. Thierry
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