On Tue, Sep 16, 2014 at 7:09 PM, Charles Steinkuehler <[email protected]> wrote: > On 9/16/2014 5:37 PM, Jason Kridner wrote: >> >> Just going along to state the obvious... >> >> eMMC and HDMI will be equally interesting tests and more practically >> useful for more capes. > > I'll try and work up a patch set for HDMI, but it won't be until tomorrow. > >> It will only be a matter of time before someone damages a board by: >> A) setting an HDMI pin to a output without disabling the HDMI > > The worst that can happen with HDMI is a bus fight (driving an HDMI pin > without first configuring the BBB side as an input). The HDMI framer > does not drive any signals back to the AM335x (other than I2C), so it > won't cause problems. If you start playing with pinmux values you could > easily see wonky video, but that's not a "break the hardware" kind of > problem.
Yeah, brainfart. Agreed, no potential damaging hardware issues. Anything like an LCD add-on board would just have inputs on those signals as well. > >> B) driving an eMMC pin into conflict without putting the eMMC in reset > > This is much more likely, and while it might not be easy to destroy the > hardware, it is probably pretty easy to corrupt the eMMC. It might be > worth requiring loading an alternate device-tree to disable the eMMC, > which can make sure it stays in reset. Getting all of those HDMI pins back for GPIO when not using HDMI w/o needing to do anything special on boot should make a lot of people happy, even if the eMMC pins aren't available. > >> I don't think there is a simple way for the current pinmux helper to >> check for these conditions, but it wouldn't hurt if any config-pin >> sort of utility would check the state of those hardware control bits >> before helping someone screw things up. :-) > > Agreed! > >> Any way you can imagine a way to keep the current uEnv.txt lines to >> disable both of those working without breaking compatibility? > > Maybe, there's some groundwork to do first. For instance I still don't > know what happens if you leave the HDMI enabled, but take all the pins > out from under it via the pinmux. I'll keep this in mind and see what I > can come up with... > > -- > Charles Steinkuehler > [email protected] > > -- > 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 [email protected]. > For more options, visit https://groups.google.com/d/optout. -- 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 [email protected]. For more options, visit https://groups.google.com/d/optout.
