Date: Fri, 03 Jan 2014 14:48:44 -0500 From: Nathan Whitehorn <nwhitehorn@freebsd.org> To: Ian Lepore <ian@FreeBSD.org> Cc: freebsd-arm@FreeBSD.org, Markus Pfeiffer <markus.pfeiffer@morphism.de> Subject: Re: FreeBSD 10 on Dockstar (Marvell Kirkwood) Message-ID: <52C7141C.2040801@freebsd.org> In-Reply-To: <1388778165.1158.302.camel@revolution.hippie.lan> References: <20131231211054.GA90299@moore.morphism.de> <1388770603.1158.273.camel@revolution.hippie.lan> <20140103175914.GC98342@moore.morphism.de> <52C70B9B.9090205@freebsd.org> <1388778165.1158.302.camel@revolution.hippie.lan>
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On 01/03/14 14:42, Ian Lepore wrote: > On Fri, 2014-01-03 at 14:12 -0500, Nathan Whitehorn wrote: >> On 01/03/14 12:59, Markus Pfeiffer wrote: >>> Hi Ian, >>> >>> On Fri, Jan 03, 2014 at 10:36:43AM -0700, Ian Lepore wrote: >>>> On Tue, 2013-12-31 at 21:10 +0000, Markus Pfeiffer wrote: >>>>> Hi all, >>>>> >>>>> I managed "fixing" it by editing the dockstar.dts file and putting for ranges: >>>>> >>>>> ranges = <0x0 0x2f 0xf9300000 0x00100000> >>>>> >>>>> Now I just have to figure out why this "fixes" it, and what damage that patch >>>>> does. >>>>> I also have some pathces for the LED on the dockstar which will tip up in my >>>>> github soon. >>>>> >>>>> Cheers, >>>>> markus >>>> After looking at the marvell code and docs, and some info I found about >>>> the dockstar at OpenWRT.org, I think the attached patch is the right fix >>>> for a dockstar (it maps the nand flash, and removes mappings for NOR >>>> flash and an LED; the dockstar doesn't seem to have NOR flash, and the >>>> LED thing seems to be out of place). >>>> >>> Can I find information anywhere as to what this ranges command actually means? >>> I was assuming it has something to do with memory mappings, but I didn't find >>> any info as to what in particular the 0x2f _means_. >>> >>> >> The ranges field, as per IEEE 1275 (page 175), provides a mapping from >> addresses in a child address space to the parent. It is a set of tuples >> of (child base address, parent base address, size), with the field >> widths being (#address-cells on this node [2], #address-cells of parent >> bus [1], #size-cells on this node [1]). This mapping table is used for >> resource allocation of children, to map bus-local requests for addresses >> to addresses on the parent bus (in this case, physical memory >> addresses). In this case, the following: >> >> ranges = <0x0 0x2f 0xf9300000 0x00100000> >> >> means that addresses 0x2f-0x0010002f in "localbus" should map linearly to physical addresses 0xf9300000-0xf9310000. This is used for drivers on the attached sub-bus so that their resources (in the "reg" properties, or in "ranges" if there are further sub-buses) can be specified in bus-local address units. The kernel code probably misinterprets it badly if changing this affects anything, which in turn implies that our kernel code is horribly bug-riddled. >> >> Note also that this replacement is not equivalent to the old mappings, since it shifts all the mappings downward by 0x20 bytes. >> -Nathan > So now we're back to the usual question... do we adhere to published or > defacto standards? The defacto standards for arm dts files are > basically "whatever linux does is right by definition" (::sigh::), and > what we've got in the marvell dts files right now is basically similar > to what linux uses (I think linux has evolved a bit since our dts files > were created; they were probably compatible at some point). > > Here's what linux is doing these days. I notice they've moved the > mapping info from "mrvl,lbc" to "marvell,kirkwood-mbus", "simple-bus"; > > https://github.com/torvalds/linux/blob/master/arch/arm/boot/dts/kirkwood.dtsi > > -- Ian > > > I don't see any particular way in which these files violate the standards. Did I miss something? In this case, so long as a 1:1 linear mapping can be made, it's perfectly alright for "child bus addresses" to be basically arbitrary codes, as here. IEEE 1275 PCI does this, for example, with 96-bit "child address" ranges that are a combination of the bus, slot, and function for the card along with actual 64-bit memory locations. In general, Linux's device tree support seems to be much more standards-compliant than ours. It's FreeBSD that seems to take the more fragile and ad-hoc approach, which is what usually creates this "I have to go patch my DTS now" problem. -Nathan
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