On Wed, Mar 05, 2014 at 07:39:26PM +0000, Russell King - ARM Linux wrote: > On Wed, Mar 05, 2014 at 07:42:28PM +0800, Shawn Guo wrote: > > It's not a hog pin, so shouldn't be added here. (Right, most of the > > existing pins shouldn't be here from the beginning) > > On the subject of that kind of thing... I have an issue with the existing > pinmux stuff. This is a wider issue than your discussion above... > > I regard the idea of requiring the pinmux to be configured as part of > the driver probe a rather broken concept - yes, it makes sense in some > scenarios, but for the vast majority of cases, it doesn't. >From what I've seen, it's the opposite - the concept works for the majority, and only some scenarios needs special handling. > > Let's take an example. A pin is wired to a SPDIF transceiver. The > out-of-reset SoC configuration results in the pin turning the LED on > in the SPDIF transceiver. > > With the way stuff is setup, with the driver having the pinmux settings > for itself, the point at which that pin gets configured is when the > driver loads, which may be a module - so that can happen quite late in > the boot sequence. A failure to boot can result in it not happening at > all. > > So, this brings up the obvious question: is this proper behaviour of the > hardware, or is this something we should do better with - such as where > we know what the settings should be for a platform, and these settings > never change, we arrange for that to happen at kernel boot time as a > once-off. > > For example, in the above case, we know it's board XYZ, we know that this > pin is connected to the SPDIF transceiver, so maybe we should configure > it early on in the boot sequence whether or not the driver has been > configured and/or loaded. For such special case, I'm fine with using hog group to handle it. But IMO, bootloader is even a better place to correct such unreasonable out-of-reset SoC configuration for particular board. Shawn -- 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
