From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Ball Subject: Re: [PATCH 1/2] sdhci: add quirk for lack of 1.8v support Date: Mon, 03 Dec 2012 14:03:28 -0500 Message-ID: <877gozj6v3.fsf@octavius.laptop.org> References: <20121125180121.31FB3FACF5@dev.laptop.org> Mime-Version: 1.0 Content-Type: text/plain Return-path: Received: from void.printf.net ([89.145.121.20]:37923 "EHLO void.printf.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751339Ab2LCTDj (ORCPT ); Mon, 3 Dec 2012 14:03:39 -0500 In-Reply-To: <20121125180121.31FB3FACF5@dev.laptop.org> (Daniel Drake's message of "Sun, 25 Nov 2012 13:01:19 -0500 (EST)") Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: Daniel Drake Cc: linux-mmc@vger.kernel.org, jrudholm@gmail.com, prakity@nvidia.com, devicetree-discuss@lists.ozlabs.org Hi, On Sun, Nov 25 2012, Daniel Drake wrote: > The OLPC XO-1.75 laptop includes a SDHCI controller which is 1.8v > capable, and it truthfully reports so in its capabilities. This > alternate voltage is used for driving new "UHS-I" SD cards at their > full speed. > > However, what the controller doesn't know is that the motherboard > physically doesn't have a 1.8v supply available. > > Add a quirk so that systems such as this one can override disable > 1.8v support, adding support for UHS-I cards (by running them at > 3.3v). > > This avoids a problem where the system would first try to run the > card at 1.8v, fail, and then not be able to fully reset the card > to retry at the normal 3.3v voltage. > > This is more appropriate than using the MISSING_CAPS quirk, which > is intended for cases where the SDHCI controller is actually lying > about its capabilities, and would force us to somehow override both > caps words from another source. > > Signed-off-by: Daniel Drake Thanks, pushed to mmc-next for 3.8. - Chris. -- Chris Ball One Laptop Per Child