On Mon, Feb 6, 2012 at 1:08 PM, Florian Fainelli <flor...@openwrt.org> wrote: > On Monday 06 February 2012 18:00:17 Peter Naulls wrote: >> On 02/06/2012 08:52 AM, jonsm...@gmail.com wrote: >> > Most ARM CPUs have boot ROMs for getting the initial image out of >> > flash. I'm referring to the boot loader that loads uboot, not uboot. >> > The ARM CPUs I've worked with search for a signature in flash, if they >> > can't find a valid signature they load from UART instead. Or you can >> > use a jumper to force loading from UART. This allows you to recover >> > from being bricked or initially load the flash without needing a >> > special programmer. >> > >> > Do the MIPS based router CPUs have this ability? What does the on MIPS >> > CPU ROM do if the image in flash is invalid? >> >> MIPS systems varies as much as ARM ones do. The short answer, is >> it depends upon the hardware. For systems which lack serial/ROM >> level recovery, you'll need to use JTAG. Some systems I work >> with lack even that. > > Actually, I have never seen a single MIPS system out there having such a boot > ROM capability.
It is a very useful ability. You can solder the flash chips on empty and then use the UART to program them during test. UART first loads a little program to tiny on-CPU-chip SRAM. This program in turns knows how to program the flash chip and then reads the full image from UART with error detection. You need the SRAM because the DRAM controller is not set up yet. u-boot support this, check out CONFIG_SPL. Takes about 30 seconds and no special equipment to initially program our ARM boards. Same procedure can unbrick them. > -- > Florian > _______________________________________________ > openwrt-devel mailing list > openwrt-devel@lists.openwrt.org > https://lists.openwrt.org/mailman/listinfo/openwrt-devel -- Jon Smirl jonsm...@gmail.com _______________________________________________ openwrt-devel mailing list openwrt-devel@lists.openwrt.org https://lists.openwrt.org/mailman/listinfo/openwrt-devel
