Messages in this thread | | | Date | Thu, 12 Jan 2012 07:56:36 +0800 | From | Shawn Guo <> | Subject | Re: [RFC PATCH v3 2/5] pinctrl: add dt binding support for pinmux mappings |
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On Wed, Jan 11, 2012 at 10:37:36AM -0800, Stephen Warren wrote: > Shawn Guo wrote at Sunday, January 08, 2012 6:56 PM: > > On Sun, Jan 08, 2012 at 08:51:59PM +0800, Richard Zhao wrote: > > ... > > > > > So, this does appear to be conflating the two things: The definition of > > > > > what pins are in a pingroup, and the mux function for a particular > > > > > setting of that pingroup. I think you need separate nodes for this. > > > > > > > > > At least for imx, we do not have mux function setting for pingroup. > > > > Instead, it only applies to individual pin. > > > I think it depends on function definition of pinmux driver. For the > > > imx example patch, it's one-to-one. > > > > It should depend on particular imx soc pinmux design rather than > > pinmux driver. If it's always one-to-one case, we do not need > > pinmux at all. Aisheng's patch just did not enumerate all the groups > > for given function. Instead, it puts a couple simple examples there > > for demonstration. > > > > ... > > > > > > > uart4func: func@1 { > > > > > func-name = "uart4"; > > > > > locations = <&bargrp &bazgrp>; > > > > > mux-value = <6 3>; > > > > > }; > > > > > > > > I prefer to have function node defined in <board>.dtsi, since it's > > > > all about defining phandle to the correct pingroup, which should be > > > > decided by board design. > > > group and function are one-to-one mapped for imx. > > > > Again, it's not the case. > > > > > So if you put function > > > in board dts, why not put pin group there too? > > > > If we put pingroup data in <board>.dts, the data will be likely get > > duplicated a lot in different board dts files. For example, if > > imx6q-sabrelite chooses the same pingroup for usdhc3 and usdhc4 as > > imx6q-arm2, the pingroup data will be duplicated between imx6q-arm2.dts > > and imx6q-sabrelite.dts. > > > > On the contrary, putting pingroup data in <soc>.dtsi and having function > > node in <board>.dts with phandle pointing to the correct pingroup will > > help avoid such data duplication. > > Oh, when I wrote in my first mail today that I'd expand on one of my > points when responding to Richard Zhao's email, I actually meant when > responding to this email. Sorry for the confusion! > > So, I don't agree with putting the "combinations" in the SoC .dtsi file, > since that could grow it into a huge file that contains a lot of nodes > that are used on some board somewhere, but typically not the "current" > board that's including it. > > However, I do see that there are probably lots of common combinations > that get re-used across multiple boards, and you might want a common > place to put those definitions so they don't need to be cut/paste > everywhere. > > So, why not create specific include files (.dtsi files) for each of those > combinations? Each include could define one particular common combination > of pin mux usage, or perhaps even a set of them if they're commonly used > together. Each board file would include the SoC .dtsi file, the relevant > set of "pinmux config" .dtsi files, and then include anything custom to > that board.
This is somehow overkilled to me. Doing this will create a big mount of .dtsi files to bloat folder arch/arm/boot/dts. Putting the 'combinations' in <soc>.dtsi seems perfect fine to me.
Regards, Shawn
> Remember, that include files simply get merged into the device > tree, so you can easily add based definitions (like) regs for e.g. an > SDHCI controller in a SoC .dtsi file, the pinmux properties in a .dtsi > file specific to SHDCI controller 3, and then e.g. CD/WP/power GPIOs in > the final board .dts file. > > Following this model, we can initially just put the pinmux config into > each board file, then factor it out into new .dtsi files as/when we see > duplication. We get to start off simple, then clean up by refactoring as > we go.
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