From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail.genesi-usa.com (mithrandir.softwarenexus.net [66.98.186.96]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTP id D3D9ADDEA3 for ; Mon, 7 May 2007 08:41:56 +1000 (EST) Message-ID: <463E59C7.9030309@genesi-usa.com> Date: Sun, 06 May 2007 23:42:15 +0100 From: Matt Sealey MIME-Version: 1.0 To: Jon Loeliger Subject: Re: [PATCH] 86xx: Enable the AC97 interface on 8641D board. References: <1178142818.32136.51.camel@ld0161-tx32> <08D3A1CE-12E0-4759-B055-DE227EA4135E@kernel.crashing.org> <1178207725.17201.33.camel@ld0161-tx32> <20070503161000.GA31881@lixom.net> <1178209046.17201.55.camel@ld0161-tx32> In-Reply-To: <1178209046.17201.55.camel@ld0161-tx32> Content-Type: text/plain; charset=UTF-8 Cc: Olof Johansson , "linuxppc-dev@ozlabs.org" List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Jon Loeliger wrote: > On Thu, 2007-05-03 at 11:10, Olof Johansson wrote: > >> This sounds like something that firmware should take care of, not >> hardcoded in the board code. Seems like the device is just a PCI device >> that doesn't have a device tree entry. > > Well, it's not a PCI device at all. A PCI Express southbridge - not much difference really is there? >> Why not do this in u-boot instead? > > Why do it there? We'd have to do it _again_ in Linux > if we didn't come in from U-Boot anyway. Because the firmware should configure the board specifics if possible, Linux should only be tweaking Northbridge/Southbridge settings if it is truly configurable at runtime or boot. If the difference is between whether an AC97 or Azalia codec is installed and soldered to the board, and it is not possible to have both, really the firmware should be setting up the chip so that only one is obviously usable. Ostensibly Linux and any drivers should be able to check which is enabled on the board - one revision may have AC97 and one may have Azalia HD audio. If this can be swapped by simply having each driver check the enabled codec mode on init, and dropping out if not correct, then it's starting to get to be Plug And Play. The alternative is that every revision of the board has it Hardcoded Into A Board Support Package, with different device trees and strange quirks which may or may not be easily determined, cluttering Kconfigs and so on. In theory; the firmware should do it, and if not, it should be done as early in Linux boot (platform init, device tree fixup) as possible. That's how we agreed to do it on the Efika after much, much discussion and argument :D -- Matt Sealey Genesi, Manager, Developer Relations