Date: Wed, 13 Feb 2013 23:53:37 -0700 From: Warner Losh <imp@bsdimp.com> To: Tim Kientzle <kientzle@freebsd.org> Cc: freebsd-arm@freebsd.org Subject: Re: building RaspPi Images Message-ID: <4EC0D89B-3B17-4650-BCCF-8CA0B83E746E@bsdimp.com> In-Reply-To: <8FD7D8A3-A1FB-4499-A411-7CEF91387FF8@freebsd.org> 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> <8FD7D8A3-A1FB-4499-A411-7CEF91387FF8@freebsd.org>
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On Feb 13, 2013, at 10:35 PM, Tim Kientzle wrote: >=20 > On Feb 12, 2013, at 10:17 PM, Warner Losh wrote: >=20 >>=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 >=20 >=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): >=20 > = https://lists.ozlabs.org/pipermail/devicetree-discuss/2012-January/012015.= html >=20 > Skimming some other discussions, it looks like the general > idea a lot of folks are considering is: >=20 > 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). >=20 > Within that node, have a collection of named pinmux settings. > E.g., pmx_ethernet01 or pmx_uart02 >=20 > Within other hardware nodes, refer to those named > settings, so you might have (very roughly; I still don't > understand FDT syntax): >=20 > uart02: uart@40800000 { > compatible =3D "=85."; > =85. > pinmux =3D "pmx_uart02"; > pinmuxc =3D "scm01"; > } >=20 > (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). >=20 > 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). >=20 > Is this generally what you had in mind? Generally, yes. The thread I had seen was a different one, but one quite = similar in tone.... Warner
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