Not touched via the DTS, but they are touched somehow. When I clear the GPIO 137 (or 138 or 139, to which I have LEDs connected) in U-Boot, the signal is correctly affected. Then I issue the boot command, and let the Linux start up. As soon as the "Starting kernel ..." message comes out on the serial port, all signals are back HIGH. So, whether there is a peripheral reset of some kind that "resets" all these GPO signals, or they are set in the C source, but they are definitely affected by kernel startup. I am OK if they came up for a little bit, as long as we had a way to set them LOW before the full system startup completes.
Thanks! On Wednesday, October 23, 2013 10:09:15 AM UTC-4, RobertCNelson wrote: > > On Wed, Oct 23, 2013 at 8:58 AM, porkupan <vladimi...@gmail.com<javascript:>> > wrote: > > Thanks, I understand. Turns out what I needed could have been > accomplished > > without rebuilding U-Boot. I had to set the value of a GPIO line, and > there > > is a U-Boot script command for that. > > > > So, a re-built U-Boot wouldn't have produced any benefit. > > > > However, I need to figure out how to force this GPIO to stay LOW during > > kernel startup. Apparently the kernel switches it HIGH (or affects some > > sort of a reset that forces GPIO_137 high). So, the GPIO line is > switched > > down via "gpio clear 137" U-Boot command, but a couple of seconds later > > comes back up, and stays up until the user software can be brought up to > > switch it off. It seems that most interactions with the registers, > > including setting GPIO levels, can be achieved via the DTS? I see some > > examples for BBB, but haven't found anything for the xM. > > Well gpio_137 is not touched on mainline: > > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/arch/arm/boot/dts/omap3-beagle-xm.dts > > > Regards, > > -- > Robert Nelson > http://www.rcn-ee.com/ > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to beagleboard+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/groups/opt_out.
