On Thu, Dec 4, 2014 at 11:27 PM, Maxime Ripard <maxime.ripard@xxxxxxxxxxxxxxxxxx> wrote: > Hi, > > On Thu, Dec 04, 2014 at 11:15:38PM +0900, Alexandre Courbot wrote: >> On Wed, Dec 3, 2014 at 1:12 AM, Maxime Ripard >> <maxime.ripard@xxxxxxxxxxxxxxxxxx> wrote: >> > On Tue, Dec 02, 2014 at 03:29:46PM +0100, Linus Walleij wrote: >> >> On Tue, Dec 2, 2014 at 3:13 PM, Alexandre Courbot <gnurou@xxxxxxxxx> wrote: >> >> > On Tue, Dec 2, 2014 at 1:36 AM, Maxime Ripard >> >> > <maxime.ripard@xxxxxxxxxxxxxxxxxx> wrote: >> >> >> >> >> The only thing I'd like to have would be that the request here would >> >> >> be non-exclusive, so that a later driver would still be allowed later >> >> >> on to request that GPIO later on and manage it itself (ideally using >> >> >> the usual gpiod_request function). >> >> > >> >> > Actually we have a plan (and I have some code too) to allow multiple >> >> > consumers per GPIO. Although like Benoit I wonder why you would want >> >> > to hog a GPIO and then request it properly later. Also, that probably >> >> > means we should abandon the hog since it actively drives the line and >> >> > would interfere with the late requested. How to do that correctly is >> >> > not really clear to me. >> >> >> >> I don't get the usecase. A hogged GPIO is per definition hogged. >> >> This sounds more like "initial settings" or something, which is another >> >> usecase altogether. >> > >> > We do have one board where we have a pin (let's say GPIO14 of the bank >> > A) that enables a regulator that will provide VCC the bank B. >> > >> > Now, both banks are handled by the same driver, but in order to have a >> > working output on the bank B, we do need to set GPIO14 as soon as >> > we're probed. >> > >> > Just relying on the usual deferred probing introduces a circular >> > dependency between the gpio-regulator that needs to grab its GPIO from >> > a driver not there yet, and the gpio driver that needs to enable its >> > gpio-regulator. >> >> I don't get it. According to what you said, the following order should >> go through IIUC: >> >> 1) bank A is probed, gpio 14 is available >> 2) gpio-regulator is probed, acquires GPIO 14, regulator for Bank B is available >> 3) bank B is probed, grabs its regulator and turn it on, probes. >> >> What am I missing? > > It would be true if bank A and B were exposed through different > drivers (or at least different instances of the same driver), which is > not the case. > > In our case, banks A and B are handled by the same instance. Ok, so both banks A and B are part of the same device/DT node. Now I think I understand the issue. You need to hog the pin so that bank B will work right after the device is probed. But you will still have the problem that the regulator device will *not* be available when your device is probed, so you cannot call regulator_get() for bank B anyway. I guess your only choice is to hog that pin and leave it active ad vitam eternam. -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
