From mboxrd@z Thu Jan 1 00:00:00 1970 From: Marc Dietrich Subject: Re: Re: [PATCH] mmc: core: Revert "skip card initialization if powerclass selection fails" Date: Mon, 02 Jul 2012 13:20:20 +0200 Message-ID: <4776161.gj4CVEvArs@fb07-iapwap2> References: <1341212194-24650-1-git-send-email-svenkatr@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7Bit Return-path: Received: from mailout-de.gmx.net ([213.165.64.22]:32959 "HELO mailout-de.gmx.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1750864Ab2GBLUY (ORCPT ); Mon, 2 Jul 2012 07:20:24 -0400 In-Reply-To: Sender: linux-mmc-owner@vger.kernel.org List-Id: linux-mmc@vger.kernel.org To: Girish K S Cc: Saugata Das , Venkatraman S , cjb@laptop.org, linux-mmc@vger.kernel.org, Ulf Hansson , Subhash Jadavani Am Montag, 2. Juli 2012, 14:28:37 schrieb Girish K S: > On 2 July 2012 14:23, Girish K S wrote: > > On 2 July 2012 14:13, Saugata Das wrote: > >> On 2 July 2012 12:26, Venkatraman S wrote: > >>> This reverts commit 3d93576e(skip card initialization if > >>> power class selection fails). > >>> Problem has been reported when this is used with eMMC4.41 > >>> card with Tegra Platform. Till the issue is root caused, > >>> bus width selection failure should not be treated as fatal. > >> > >> According to me, we need to find the root issue (which could be either > >> host not able to provide enough current or faulty eMMC). Do we know, > >> what could be the side effect of working on eMMC with less power than > >> what it has requested in PWR_CL ? > >> > >> One known issue with the current power class selection is that we do > >> not check the current requirement for a selected power class. It > >> assumes that host is able to provide the maximum current needed at > >> highest speed (> 800mA). Is it already checked on Tegra ? > > > > and at the least bus width i.e 1 bit mode. > > The MMC card spec has 2 max current values (power class) one for 4 bit > mode and another for 8 bit mode at supported voltages. But the SDHCI > spec has one MaxCur register for supported voltages but doesnt mention > for which bus width. Any input on this is very helpful to resolve the > powerclass issue that is pending the higher nibble is for 8 bit and the lower one for 4 bit. The power class is same for both bus width on this toshiba device. Marc