From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754629AbYCTH1h (ORCPT ); Thu, 20 Mar 2008 03:27:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752625AbYCTH10 (ORCPT ); Thu, 20 Mar 2008 03:27:26 -0400 Received: from moutng.kundenserver.de ([212.227.126.171]:62019 "EHLO moutng.kundenserver.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752613AbYCTH1Z (ORCPT ); Thu, 20 Mar 2008 03:27:25 -0400 Date: Thu, 20 Mar 2008 08:27:13 +0100 (CET) From: Bodo Eggert <7eggert@gmx.de> To: Wappler Marcel cc: 7eggert@gmx.de, Pierre Ossman , linux-kernel@vger.kernel.org Subject: RE: MMC: Card detection through pin CD/DAT3 issue In-Reply-To: <83116F0A4FF67A4F97BA0B6E408C48E301DAB652@zuerich.BC-Int.NET> Message-ID: References: <83116F0A4FF67A4F97BA0B6E408C48E301DAB652@zuerich.BC-Int.NET> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=us-ascii X-be10.7eggert.dyndns.org-MailScanner-Information: See www.mailscanner.info for information X-be10.7eggert.dyndns.org-MailScanner: Found to be clean X-be10.7eggert.dyndns.org-MailScanner-From: 7eggert@gmx.de X-Provags-ID: V01U2FsdGVkX19TeSWAb8tRVoTEVi6MKywmoslPzjzv5fhCvMr JCyg0UQ7N8KMEyu7R8aXfRyL65tyWdoS+gadciXmLkTGH/l8fm kjwbX3wJWYiEeVJst0icA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 19 Mar 2008, Wappler Marcel wrote: > Bodo Eggert wrote: > >> I have found this requirement in the SD host controller spec: > >> "The card detect is active regardless of the SD Bus Power." > >> > >> I wonder how the card should be able to pull up the CD/DAT3 Pad to > >> VCC if its only VCC pad is not connected to VCC due to the fact that > >> the host controller has switched off the cards power - any idea how > >> this could be managed? > > > If the VCC pin is connected to 0 V, the "pullup" will pull > > down to 0V. > > If the controller reverses it's logic while VCC=0, it might work. > > I am concerned that in this case there would be neither a pull > up nor a pull down at this signal. Due to floating gates that input > could lead to millions of "card detection" events a second, if As long as no card is inserted, the pin on the controller would be floating and generating the same amount of interrupts, unless there is a (weak) internal pulldown. You can do the same for the reversed logic, using an internal pullup and abusing the card's pullup as a pulldown. -- Never forget that your weapon is made by the lowest bidder.