Date: Wed, 13 Feb 2013 21:35:38 -0800 From: Tim Kientzle <kientzle@freebsd.org> To: Warner Losh <imp@bsdimp.com> Cc: freebsd-arm@freebsd.org Subject: Re: building RaspPi Images Message-ID: <8FD7D8A3-A1FB-4499-A411-7CEF91387FF8@freebsd.org> In-Reply-To: <20ABD94C-206C-4936-BAE7-88D379F27B74@bsdimp.com> References: <5116CB50.9080303@ceetonetechnology.com> <7757848F-45C6-4DEF-A4A2-5F900EB10A06@kientzle.com> <20130210012052.4d7e1a46@ivory.local> <58DCA6BE-8C06-4F69-81A2-A3582FBB5B12@kientzle.com> <E691571B-EA19-4485-BB02-7486685B44C7@bsdimp.com> <1360598511.4545.92.camel@revolution.hippie.lan> <DCA761EF-FAE4-4BC9-AE33-D9F55C8ABB16@bsdimp.com> <1360600007.4545.98.camel@revolution.hippie.lan> <3F4CD7E5-17D4-4315-86BD-605F5C0040DC@kientzle.com> <1360604561.4545.115.camel@revolution.hippie.lan> <72554169-D2DD-48DD-8C2F-6C411DBFCE4D@kientzle.com> <FB6E9736-F961-4685-9502-AA5AC17D9F29@bsdimp.com> <25EAEA1F-876A-4189-BCD4-A7D438332C11@kientzle.com> <5F763292-2EA4-426A-B84A-8DE533BA6308@bsdimp.com> <ABD39555-BE26-4CE3-9133-85427448ACF9@freebsd.org> <20ABD94C-206C-4936-BAE7-88D379F27B74@bsdimp.com>
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On Feb 12, 2013, at 10:17 PM, Warner Losh wrote: >=20 > On Feb 12, 2013, at 10:30 PM, Tim Kientzle wrote: >=20 >> On Feb 12, 2013, at 10:45 AM, Warner Losh wrote: >>=20 >>> But it doesn't have all the pin group stuff in yet, so I'll have to = chase that down and see what happened to that part of the early patches = I was reviewing=85 >>=20 >> I would be interested in seeing those early patches. >>=20 >> I agree that it would be best to bundle pinmux info >> with the related device in the FDT. Seeing some >> prior art would help a lot. >=20 > They were posted to the device-tree mailing list a while ago, but I = don't have a pointer to the archives :(... They were from somebody at = Atmel.com, so if you find it, it will be easy to search for. >=20 > Warner >=20 I finally found the thread I think you're referring to, from January 2012. This looks like an interesting post because it gives some concrete ideas for what the device tree might look like (and the author gives some thoughtful critiques that I'll have to think about further): = https://lists.ozlabs.org/pipermail/devicetree-discuss/2012-January/012015.= html Skimming some other discussions, it looks like the general idea a lot of folks are considering is: Having a pinmux node for whatever hardware controls pinmuxing. For the TI chip I'm working with, that would be the scm (System Control Module). Within that node, have a collection of named pinmux settings. E.g., pmx_ethernet01 or pmx_uart02 Within other hardware nodes, refer to those named settings, so you might have (very roughly; I still don't understand FDT syntax): uart02: uart@40800000 { compatible =3D "=85."; =85. pinmux =3D "pmx_uart02"; pinmuxc =3D "scm01"; } (That is, the uart02 should use scm01 to enable pmx_uart02 pinmux settings.) In particular, for hardware with multiple states, you could refer to multiple pinmux settings (e.g., an idle setting that tristated the outputs vs. an active setting that powered them). A lot of the debate seems to revolve around the details of whether the pinmux details should be lists of hardware numeric codes (advantage: eliminates tables from the pinmux driver source and eliminates lots of text from the DTS) or should be more verbose textual descriptions (advantage: easier to read and update). Is this generally what you had in mind? Tim
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