Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934800AbXHGO5A (ORCPT ); Tue, 7 Aug 2007 10:57:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S934428AbXHGO4m (ORCPT ); Tue, 7 Aug 2007 10:56:42 -0400 Received: from cluster-g.mailcontrol.com ([85.115.41.190]:44638 "EHLO cluster-g.mailcontrol.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934325AbXHGO4k (ORCPT ); Tue, 7 Aug 2007 10:56:40 -0400 Message-ID: <46B885CC.6030404@csr.com> Date: Tue, 07 Aug 2007 15:46:36 +0100 From: David Vrabel User-Agent: Thunderbird 1.5.0.12 (X11/20070604) MIME-Version: 1.0 To: Pierre Ossman CC: linux-kernel@vger.kernel.org Subject: Re: [patch 4/4] sdio: disable CD resistor References: <11858961933491-git-send-email-david.vrabel@csr.com> <20070804152304.65ed8f1b@poseidon.drzeus.cx> <46B6F877.7060504@csr.com> <20070806171207.59fafa18@poseidon.drzeus.cx> <46B73F18.5030109@csr.com> <20070806220145.66b97559@poseidon.drzeus.cx> <46B86ADB.90000@csr.com> <46B86BDF.8050700@csr.com> <20070807154342.47f63cfe@poseidon.drzeus.cx> In-Reply-To: <20070807154342.47f63cfe@poseidon.drzeus.cx> Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 07 Aug 2007 14:46:42.0915 (UTC) FILETIME=[C5261330:01C7D901] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1457 Lines: 40 Pierre Ossman wrote: > On Tue, 07 Aug 2007 13:55:59 +0100 > David Vrabel wrote: > >> sdio: disable CD resistor >> >> Disable the card detect resistor to ensure all data lines are equally >> loaded. Not doing this can have a negative impact on buses with >> marginal signal quality. >> >> Signed-off-by: David Vrabel > > I'm not sure about this. I've seen several hosts which lack a > mechanical detect switch. If host is correctly designed it will have identical pull-ups on all the DAT lines, and therefore this internal pull-up should be disconnected. However, given that disabling the pull-up may cause 4 bit transfers to fail on hardware that omits a host-side pull-up on DAT3 I agree that the resistor should remain enabled. Is there an example driver for a host that uses pin 1/DAT3 sensing for card detection? I'm curious about how removal detections work. App Note on card detection goes into the use of this resistor in more detail but I don't believe this document is publicly available :(. David -- David Vrabel, Software Engineer, Drivers group Tel: +44 (0)1223 692562 CSR plc, Churchill House, Cambridge Business Park, Cowley Road, CB4 0WZ . - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/