Hi Stephen, On Thu, Nov 15, 2012 at 3:46 PM, Stephen Warren <swar...@wwwdotorg.org> wrote: > On 11/15/2012 04:31 PM, Simon Glass wrote: >> Hi Stephen, >> >> On Wed, Oct 31, 2012 at 9:50 PM, Stephen Warren <swar...@wwwdotorg.org> >> wrote: >>> On 10/31/2012 05:59 PM, Simon Glass wrote: >>>> Hi, >>>> >>>> On Fri, Oct 26, 2012 at 12:17 AM, Lucas Stach <d...@lynxeye.de> wrote: >>>>> Am Donnerstag, den 25.10.2012, 19:31 -0700 schrieb Simon Glass: >>>>>> From: Sean Paul <seanp...@chromium.org> >>>>>> >>>>>> Add get and set gpio functions to fdtdec that take into account the >>>>>> polarity field in fdtdec_gpio_state.flags. >>>>>> >>>>> In another thread Stephen Warren and I came to the conclusion that we >>>>> most likely should remove this polarity flag from the GPIO bindings. >>>>> >>>>> Currently it is only for the USB VBUS GPIO which should move over to >>>>> regulators once they land in U-Boot. Do you have any other applications >>>>> for this flag, so we might reconsider removing it? >>>>> >>>> >>>> Well, any time you have a flag which is inverted in meaning, it can be >>>> useful. We have several switches on the board which can be active high >>>> or low, and polarity is used for that. >>>> >>>> In fact, it would be nice IMO to be able to specify input/output as >>>> well. I know the exynos bindings do this. There is a noddy function >>>> called fdtdec_setup_gpio() in U-Boot which really needs to be sorted >>>> out. I discussed with Stephen some time ago how GPIOs should be >>>> SOC-specific and it should be possible to set up a GPIO with a single >>>> call, as Linux does. The more information there is in the binding, the >>>> more it can do automatically. >>>> >>>> Does the Tegra Linux GPIO binding still have a polarity? >>> >>> Yes it does, although in practice it can't be used (and hence should >>> really be removed), since not all GPIO bindings have such a flag, so >>> there is always a need for a separate property to indicate the polarity >>> (c.f. fixed-regulator with GPIO control bindings for example). >>> >> >> I've had a bit of time to look into this. I see that the regulator >> framework in the kernel seems to be used for various control purposes, >> and provides useful polarity stuff. I was rather hoping that GPIOs >> could be a bit more high level in U-Boot, with information about: >> >> - input/output >> - drive strength >> - polarity >> - pull up/down >> >> In fact most of these are actually supported in most kernel bindings, >> but of course it is binding-specific. Would it be useful to ask for a >> polarity setting in the GPIO. When it is not available, the polarity >> would then always be normal. >> >> This might avoid moving polarity and input/output selecting down into >> each client of the gpio, which seems undesirable in general. >> >> Should we consider a second level of indirection for GPIOs to support >> these non-binding features? It seems a bit complicated though. >> >> However, if it is too late to do this, or not desirable for some >> reason, then we should just drop this patch. > > The issue may not be bad enough we have to drop flag usage. It's also > being discussed at: > > http://www.spinics.net/lists/arm-kernel/msg206299.html > > I'd recommend seeing how that pans out before making a decision whether > to start/keep using flags or not. >
Thanks, will await news. Regards, Simon _______________________________________________ U-Boot mailing list U-Boot@lists.denx.de http://lists.denx.de/mailman/listinfo/u-boot
