On Tue, Apr 5, 2016 at 12:40 AM, Mark Brown <broonie@xxxxxxxxxx> wrote: > On Thu, Mar 31, 2016 at 02:44:41PM +0300, Irina Tirdea wrote: > >> This is a proposal for adding ACPI support for pin controller >> configuration. > >> It has been developed to enable the MinnowBoard and IoT community >> by providing an easy way to specify pin multiplexing and >> pin configuration. > > So this is mainly targeted at modules being added to base boards? That is the main use case, yes. Velocity of platform debugging/enabling is another one. > Without getting into the binding at all here it seems like this is not > solving the problem at the right abstraction level. It's exposing the > pins on the SoC directly without any tie in with the functionality that > goes over those pins. This is not completely true. The pinctrl drivers are exposing functionality in terms of function groups (e.g., i2c1_grp, spi1_grp, pwm1_grp, etc.) It is not enough, but it is a step in the right direction for standard bindings and for tools that can build on top of this. > This means that any binding of a board to an ACPI > using system that just uses this is going to be entirely specific to the > particular combination of base and expansion board even if the > electrical connections are standard. > This can be solved by tools that work with high level abstractions and generate this specific information. > This is something that people are currently looking at for DT, there the > discussion has been about defining the connectors as entities and hiding > the details of the muxing on the SoC behind that along with higher level > concepts like instantiation of buses like I2C and SPI. It seems like if > we do want to try to share between DT and ACPI we should be doing it at > that level rather than dealing with pinmuxing at the extremely low level > that pinctrl does. > At some point we still need to poke registers. We already have a drivers that do this (pinctrl) and a standard configuration interface (the pinctrl device tree bindings). It seems natural to build on top of this for those higher level concepts / tools. > Obviously for the more general ACPI use case the idiomatic way of > handling this is that the OS should never see anything about the > pin muxing. With DT we need to really know what's going on with the > pinbox because the model is that even for things built into a single > board the OS is responsible for managing the pins but that's really not > how ACPI is expected to work. Maybe. But we already expose pin control / muxing in drivers/pinctrl/intel, yes, read-only at this point. Very useful for debugging. Having write access would make debugging even more useful, not to mention fast prototyping. -- 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
