Date: Sun, 19 Aug 2012 20:07:27 -0600 From: Warner Losh <imp@bsdimp.com> To: Ian Lepore <freebsd@damnhippie.dyndns.org> Cc: Tim Kientzle <tim@kientzle.com>, freebsd-arm@freebsd.org, gonzo@freebsd.org Subject: Re: gpiobus_hinted_child >32 pins support, pin_getname method, and gpio-sysctl bridge patch Message-ID: <B53D4177-C854-4937-8D7D-C77A86697F1C@bsdimp.com> In-Reply-To: <1345420932.27688.298.camel@revolution.hippie.lan> References: <20120819.171723.523519054460575158.hrs@allbsd.org> <8CDAB51C-14A0-42F0-8E16-43A3EABA2703@bsdimp.com> <E7C5ED5C-7120-4B69-9146-D9CC7A8E14C2@kientzle.com> <7E6C76BE-1D3F-40E4-BFE3-DC88715C234C@bsdimp.com> <12A967D8-BC49-49AF-BBD9-40E259932617@kientzle.com> <974EEF9B-08C2-4876-9223-48DD4ABDFC99@bsdimp.com> <1345420932.27688.298.camel@revolution.hippie.lan>
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On Aug 19, 2012, at 6:02 PM, Ian Lepore wrote: > On Sun, 2012-08-19 at 17:42 -0600, Warner Losh wrote: >> On Aug 19, 2012, at 5:04 PM, Tim Kientzle wrote: >>=20 >>> On Aug 19, 2012, at 10:02 AM, Warner Losh wrote: >>>>=20 >>>> On Aug 19, 2012, at 10:03 AM, Tim Kientzle wrote: >>>>=20 >>>>> On Aug 19, 2012, at 8:38 AM, Warner Losh wrote: >>>>>=20 >>>>>>=20 >>>>>> In general, I like this code in the context of the current GPIO = framework. I've been growing dissatisfied with the current GPIO = framework, however, and some of my comments reflect that more than any = comments about this specific code. >>>>>=20 >>>>> I noticed that Linux on BeagleBone does not >>>>> simply number all pins as we do. Pins are identified by >>>>> two numbers: a unit number and a pin number. >>>>=20 >>>> Is this in the code, or just in the FTD? On Atmel, there's a = single number from 0 to max-1 with all negative numbers being invalid. = But Atmel doesn't have proper FTD support in Linux just yet (3.5 has a = good start, and 3.6 will add the missing pinmux/pinctl stuff). >>>=20 >>> I'm not exactly sure what you mean. The Linux DTS file: >>>=20 >>> = http://git.kernel.org/?p=3Dlinux/kernel/git/torvalds/linux.git;a=3Dblob;f=3D= arch/arm/boot/dts/am335x-bone.dts >>>=20 >>> inherits most of the real functionality from >>>=20 >>> = http://git.kernel.org/?p=3Dlinux/kernel/git/torvalds/linux.git;a=3Dblob;f=3D= arch/arm/boot/dts/am33xx.dtsi >>>=20 >>> There are certainly separate entries there for each GPIO module. I = presume (but haven't verified) that the unit number maps directly to a = "gpio#" device name. >>=20 >> There's similar things in the Atmel DTS files, but under the covers = the gpio pins map into a uniform space number 0 to 32*N-1, where N is = the number of GPIO units. >=20 > The possibility exists that there can be sets of gpios managed by > different hardware that's completely unrelated. For example, you can > have some number of gpio pins on an SoC, then have an iicbus device = that > provides a bunch more gpio pins. I'm not sure whether or not that > confounds the idea of having a big zero-N address space for naming = pins. Not really. Like interrupts, they can come from many different sources. = Yet, IRQs are well ordered. Each platform defines how they are = numbered differently, and I wasn't suggesting that the Atmel mapping = would be universal. The mapping is just a by the way this is one way it = is done, not this is the only, or best, way to do it everywhere. > Another annoying complexity is IRQs associated with pins. Some pins = can > directly generate IRQn on the SoC. Other pins are grouped together by > device or bank or whatever, such that any change on pins M-N generates > IRQn. Sharing the IRQ for the latter type between multiple drivers > (each using one or more pins in the shared bank) can be tricky, = because > on some hardware, reading the status register that says which pins > changed clears that register. It is no trickier than sharing it back in the at-pic days. > I have no solutions to offer here, just throwing out a couple things > I've run into in the past couple years. Understood.=
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