Date: Sat, 2 Feb 2013 12:03:56 -0800 From: Tim Kientzle <tim@kientzle.com> To: Ian Lepore <ian@freebsd.org> Cc: freebsd-arm@freebsd.org Subject: Re: Beaglebone Serial Ports Message-ID: <66029B5F-2A19-4683-B589-814932E156A2@kientzle.com> In-Reply-To: <1359818003.93359.381.camel@revolution.hippie.lan> References: <510CE8E0.9070102@g7iii.net> <1359818003.93359.381.camel@revolution.hippie.lan>
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On Feb 2, 2013, at 7:13 AM, Ian Lepore wrote: > On Sat, 2013-02-02 at 10:22 +0000, Iain Young wrote: >> Hi Folks, >> >> Just a quick question with regards to some clarification serial ports >> on the Beaglbone and FreeBSD. Am I correct in deducing that FreeBSD >> lacks support for UARTS1 thru 5 at the moment ? >> >> I can see what I believe to be UART0 (which is attached to the USB) as >> /dev/cuau0, but not the others. A few finds and greps through the >> kernel source didn't show up anything obvious either. >> >> Is any one working on them ? Or is there a kernel module or option >> that I need to enable for them to build ? It should just be a matter of updating the DTS file with additional UART entries and updated pinmux. Unfortunately, the current BeagleBone builds use a compiled-in device tree, so you'll have to edit the DTS file at sys/boot/fdt/dts/beaglebone.dts and then rebuild the kernel. I'd like to move that out of the kernel; the loader already has logic to load a DTS file and pass it to the kernel, it should just need some tinkering with loader.rc to get it working. That would make it a lot easier to tweak settings on a per-system basis without having to rebuild the kernel. > According to the datasheet all the onboard uarts should be supported by > our standard uart driver (but only uart1 has all the modem-control lines > wired). Two things need to be done to enable them: add entries to > the .dts file (easy), and configure the multipurpose pins for them at > runtime. I have no idea how we handle the latter in the FDT world. In > the pre-FDT world it was pretty much ad-hoc and board-support routines > that ran at startup configured pins for that board. The pinmux for BeagleBone is in the DTS file, specifically, the scm@44e10000 section. The pad-config section is parsed by general code in sys/arm/ti/ti_scm.c driven from an SoC-specific table in sys/arm/ti/am335x/am335x_scm_padconf.c. I don't know offhand if there is currently a mechanism for changing pinmux at runtime. It would certainly be nice to have such a mechanism. Tim
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