The pin direction is only relevant for GPIO. For subsystems like SPI, the pin direction is defined by the subsystem, not the pin direction defined by pinctrl-single.
Regards, John > On Mar 7, 2017, at 2:40 PM, Jon Turner <jonturne...@gmail.com> wrote: > > The overlay for the SPI0 interface includes the following lines > pinctrl-single,pins = < > 0x150 0x30 /* spi0_sclk, INPUT_PULLUP | MODE0 */ > 0x154 0x30 /* spi0_d0, INPUT_PULLUP | MODE0 */ > 0x158 0x10 /* spi0_d1, OUTPUT_PULLUP | MODE0 */ > 0x15c 0x10 /* spi0_cs0, OUTPUT_PULLUP | MODE0 */ > >; > > Notice the first line, which specifies that the spi0 clock signal is an input > with a pullup enabled. > This does not make sense to me, since every diagram I have seen (for example > in Derek Molloy's > book, Exploring Beaglebone) shows the clock signal as an output from the > BeagleBone. I have checked > the BeagleBone schematic and the processor pin for this signal connects only > to the P9 header. > So the only way it would make sense for this pin to be an input is if the > user is expected to have > a clock generation circuit on the cape. It's hard for me to imagine that this > is the intended usage. > > I have seen this same configuration for the overlay in multiple places, so I > am guessing it is > correct, but I cannot understand why. Can someone knowledgable out there > please enlighten me? > > Thanks, > > Jon Turner > > > -- > For more options, visit http://beagleboard.org/discuss > <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 > <mailto:beagleboard+unsubscr...@googlegroups.com>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagleboard/55a9f2a1-abf0-4225-8b55-e2cdc27eeb47%40googlegroups.com > > <https://groups.google.com/d/msgid/beagleboard/55a9f2a1-abf0-4225-8b55-e2cdc27eeb47%40googlegroups.com?utm_medium=email&utm_source=footer>. > For more options, visit https://groups.google.com/d/optout > <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 beagleboard+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/C40C55F7-06F8-4520-8287-86281FBA7632%40gmail.com. For more options, visit https://groups.google.com/d/optout.
