From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Subject: Re: USB support on mpc5200 broken From: Benjamin Herrenschmidt To: Matt Sealey In-Reply-To: <48E243C5.7000100@genesi-usa.com> References: <9e4733910809241451x7492d2a9s56b4cb4ee0fe0244@mail.gmail.com> <9e4733910809241809r58bddc2ax4759b70c3f07f6cf@mail.gmail.com> <1222307447.8277.147.camel@pasglop> <48E02FD0.8000809@genesi-usa.com> <20080929034329.GB8694@yookeroo.seuss> <9e4733910809290714td2dc6cclecf2e2b080a80ca1@mail.gmail.com> <48E243C5.7000100@genesi-usa.com> Content-Type: text/plain Date: Wed, 01 Oct 2008 13:31:41 +1000 Message-Id: <1222831901.12264.8.camel@pasglop> Mime-Version: 1.0 Cc: linuxppc-dev , David Gibson Reply-To: benh@kernel.crashing.org List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , > This is what we were recommended to use at the time. There is a patch > on www.powerdeveloper.org which tweaks the tree to make it ultra-compliant > with the Linux version of things, which implements every variation. It > also implements a suggested patch which added a "big-endian" property > (not built in to the compatible property, but another property). > > I don't see why THAT patch got reverted as it was a great idea that we > all agreed was a great idea. I agree. Something needs to be fixed on the OHCI OF stuff, it should definitely cope with the "big-endian" property (which is a practice borrowed from Apple that I recommended I think back then) and I don't see any problem with having ohci-be in the "compatible" property, its trivial enough to cope in the driver and being anal about it on the kernel side doesn't really bring any benefit. Care to send a patch ? > Linux development around here is getting really schizophrenic. Nobody > is writing these decisions down even as comments in the source code.. That isn't entirely true. There's the ePAPR effort on power.org that is codifying a lot of that, and there are binding documents dropped in Documentation/powerpc. > No; you can have little endian OHCI controllers on big endian machines. > It's a property of the host controller, not the system architecture, just > like PCI is always little endian (except when you have magic in hardware > like Amiga PowerUP cards which endianswap for you :) In fact, you can have both kinds on the same machine. Note about the Amiga stuff: it's a bad idea :-) Every attempt at "magically" fixing endian in HW is a recipe for tears and disasters. Approximately ... always. The only cases that I know that have a remote chance of being useful are specifically programmable swappers on a given device or per-page endian configuration in the processor (like BooKE). Cheers, Ben.