From owner-freebsd-arm@FreeBSD.ORG Thu Jun 7 20:02:19 2007 Return-Path: X-Original-To: arm@freebsd.org Delivered-To: freebsd-arm@FreeBSD.ORG Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 3613D16A421 for ; Thu, 7 Jun 2007 20:02:19 +0000 (UTC) (envelope-from imp@bsdimp.com) Received: from harmony.bsdimp.com (bsdimp.com [199.45.160.85]) by mx1.freebsd.org (Postfix) with ESMTP id E0C9B13C4B7 for ; Thu, 7 Jun 2007 20:02:18 +0000 (UTC) (envelope-from imp@bsdimp.com) Received: from localhost (localhost [127.0.0.1]) by harmony.bsdimp.com (8.13.8/8.13.4) with ESMTP id l57K0sM6082081; Thu, 7 Jun 2007 14:00:54 -0600 (MDT) (envelope-from imp@bsdimp.com) Date: Thu, 07 Jun 2007 14:00:54 -0600 (MDT) Message-Id: <20070607.140054.74667648.imp@bsdimp.com> To: nb@synthcom.com From: Warner Losh In-Reply-To: <20070607123930.E75948@synthcom.com> References: <49754.2001:6f8:101e:0:20e:cff:fe6d:6adb.1181244172.squirrel@webmail.alpha-tierchen.de> <20070607.133456.74668036.imp@bsdimp.com> <20070607123930.E75948@synthcom.com> X-Mailer: Mew version 3.3 on Emacs 21.3 / Mule 5.0 (SAKAKI) Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-2.0 (harmony.bsdimp.com [127.0.0.1]); Thu, 07 Jun 2007 14:00:54 -0600 (MDT) Cc: arm@freebsd.org Subject: Re: 4-bit SD Card mode X-BeenThere: freebsd-arm@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Porting FreeBSD to the StrongARM Processor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 07 Jun 2007 20:02:19 -0000 From: Neil Bradley Subject: Re: 4-bit SD Card mode Date: Thu, 7 Jun 2007 12:46:37 -0700 (PDT) > > I'm not sure I like this at all. The devices shouldn't be setting up > > the pins for that device. In some cases, they can't know how to do > > that, and this is one of them. The device has no way of knowing if > > all 4 wires are connected, or just 1 and the 'spare' lines are used > > for GPIO. > > Not doing it will irritate more people (i.e. "I'm not getting full speed > out of the SD card). While it's a valid concern, I don't think it's > unrealistic to assume that all 4 DAT lines are hooked up. I've not yet > encountered a design that A) had SD capabilities, B) was only running > single bit because of a lack of GPIOs. I'm not saying that we only hook up the one data. I'm saying that we force the boot loader to do it, or as a fallback a board specific routine. The driver shouldn't be in the business of doing it. My hardware guys are somewhat agressive in their elimination of "unused" lines. We multiplex TX/RX from one of the serial ports to be GPIO lines dynamically at run time depending on what add-in hardware is connected to the box. I want to keep things as flexible as possible because I know that other designs are doing similar "icky" things. Warner