Messages in this thread | | | Date | Fri, 9 Dec 2011 09:53:27 -0800 | From | Tony Lindgren <> | Subject | Re: [PATCH] [RFC] pinctrl: add a driver for Energy Micro's efm32 SoCs |
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* Tony Lindgren <tony@atomide.com> [111209 08:53]: > * Stephen Warren <swarren@nvidia.com> [111209 08:17]: > > Dong Aisheng wrote at Friday, December 09, 2011 8:03 AM: > > ... > > > I agree that parsing data from device tree increases much effort > > > because we can not using any help functions like microes in dts file and we have > > > to construct the structure we need in driver by parsing that data. > > > And it will increase dtsi file's size a lot when after adding all functions. > > > > > > I wonder if we can define that data as a pdata in a .c file and only > > > get a pointer from dts file. That would make life much easier. > > > > You can't get pointers themselves directly from a .dts file, since the > > .dts file author has no idea what the memory layout (or even which OS) > > is present on the running system. > > > > An alternative is to key off the compatible flag in the device tree, > > and use that to index a table that points at the various structures you > > want pointers to. > > > > struct of_device_id's .data field, and the function of_match_device() > > are for exactly that purpose; see the way the Tegra pinctrl driver that > > I posted uses them for an example of mapping compatible flag to per- > > SoC initialization function pointers. > > For letting a device do it's pingroup in DT, I've played with the > following: > > /* mux func phandle mux func name hw initial flags */ > pins = <&uart3_rx_irrx>, "uart3_rx_irrx", <0xdeadbeef>, > <&uart3_tx_irtx>, "uart3_tx_irtx", <0xdeadbeef>; > > But it seems that doing mixed-property arrays gets nasty as any > data after a string has a high likelihood of getting misaligned > since a mixed-property array is a string array with the string > embedded in it with the registers. That leads into nasty string > parsing that can be extremely flakey with buggy DT data. So it > seems that using a string there is only safe as the last element, > which means we can't use names for multiple pins. > > So I've pretty much come to the conclusion that we would have to > use something like this instead: > > /* phandle f hw specific initial flags */ > pins = <&uart3_rx_irrx 0 0xdeadbeef > &uart3_tx_irtx 0 0xdeadbeef>; > > This however has a problem for cases where we may not have a phandle > in DT for the mux function. For example, let's assume that we'll have > tens of thousands of lines of mux data for omaps (we already have > over 6k LOC) and just want to load that from /lib/firmware to avoid > bloating the kernel. In that case we won't have the phandle for the > mux function in DT. > > It would be _really_nice_ to use DT in the missing phandle case also > for doing the device to mux function mapping based on a function name > when no phandle is available. > > But so far I have not found a good way of doing both phandle and > optional name type thing. Anybody got some good ideas for that?
Oh forgot to mention of course what Benoit came up which is reg-names. That of course is doable with both phandles and pin names:
So optionally either
pins = <&uart3_rx_irrx &uart3_tx_irtx>; or
pin-names = "uart3_rx_irrx", "uart3_tx_irtx";
and both pins and pin-names could have optional hardware specific board default flags:
pin-flags = <0xdeadbeef 0xdeadbeef>;
The pin-flags could end up being defines if dtc will at some point support preprocessing the .dtc files.
> BTW, this same problem applies also to clock framwork where we may > have multiple sources of clocks to register and map to devices.
Regards,
Tony
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