On 16.11.2018 09:25, Uwe Kleine-König wrote: > On Fri, Nov 16, 2018 at 08:34:30AM +0100, Lothar Waßmann wrote: >> Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx> wrote: >>> On Thu, Nov 15, 2018 at 04:25:45PM +0100, Thierry Reding wrote: >>>> On Wed, Nov 14, 2018 at 10:51:20PM +0100, Uwe Kleine-König wrote: >>>>> On Wed, Nov 14, 2018 at 12:34:49PM +0100, Thierry Reding wrote: >> [...] >>>>> Also dts writes don't need to lookup the needed GPIO numbers and pinctrl. >>>> >>>> Just to clarify: I don't think that we need to get the GPIO number >>>> involved in this case, because we don't have to reconfigure the pin as >>>> GPIO to make this work. The only reason that Michal's proposal did that >>>> is because that was believed to be necessary. But if the pin can just be >>>> configured with a 100k pull-up, that's enough to pull the pin high when >>>> we need it. Thierry, I have to disagree here. I do not really know how to activate the internal pull-up without requesting the GPIO and configuring the pin as *input*. And to do it the GPIO number needs to be specified in DT. >>> Unless the gpio happens to be configured as output at the wrong value. >>> Further I'm not sure if the pwm in disabled state actively pulls to 0 >>> and if in this state the PU of the pin is good enough to ensure a one >>> here. That would need verification first. >> >> No. You can disable the output driver via pinctrl, so that only the >> selected pull-up/down is relevant. The pin function and GPIO register >> settings don't matter at all in this case. Lothar, please can you be more specific how would you do that? IFAIK the pull-up/down internal resistors have effect only if the pin is configured as GPIO *input* (on i.MX6 at least). See the TRM, 29.4.2.2 Output driver: "Internal pull-up, pull-down resistors, and pad keeper are disabled in output mode." > Is this about DSE=HI-Z in the pad control register? I didn't know about > this. I see this exists on i.MX6 but not on i.MX25. Also i.MX51 doesn't > seem to have this feature. Uwe, I also did not find the DSE option on other SoCs in their respective manuals and source code. But even if it would be available on all SoCs I still think it is not enough. Best regards, Michal
