From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756739Ab1GDIzI (ORCPT ); Mon, 4 Jul 2011 04:55:08 -0400 Received: from mho-04-ewr.mailhop.org ([204.13.248.74]:31227 "EHLO mho-02-ewr.mailhop.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756632Ab1GDIzH (ORCPT ); Mon, 4 Jul 2011 04:55:07 -0400 X-Mail-Handler: MailHop Outbound by DynDNS X-Originating-IP: 98.234.237.12 X-Report-Abuse-To: abuse@dyndns.com (see http://www.dyndns.com/services/mailhop/outbound_abuse.html for abuse reporting information) X-MHO-User: U2FsdGVkX1/RUiH4/btFgWhtATu98QnW Date: Mon, 4 Jul 2011 01:55:04 -0700 From: Tony Lindgren To: Paul Walmsley Cc: linux-omap@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Rajendra Nayak , =?utf-8?Q?Beno=C3=AEt?= Cousson , Michael Buesch Subject: Re: [PATCH] OMAP: hwmod: add kernel cmdline flag to avoid resetting IP blocks during init Message-ID: <20110704085503.GQ23145@atomide.com> References: <20110703010204.19046.85186.stgit@dusk> <20110703010206.19046.85293.stgit@dusk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110703010206.19046.85293.stgit@dusk> User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Paul Walmsley [110702 17:58]: > On some boards, it's not possible to reset certain IP blocks during > kernel initialization. Some boards connect GPIO lines to external > voltage controllers, so resetting them may cause voltage to drop on a > critical supply[1]. Other boards connect GPIO lines to reset pins on > external devices without open documentation, so if the GPIO blocks are > reset, the external devices cannot currently be reconfigured[2]. > > The correct way to fix these issues on OMAP is to add a > hwmod_no_setup_reset(hwmod) call to the board file, that references > the IP block that must preserve its state. This allows the OMAP core > code to reset the remaining IP blocks. > > However, during initial bring-up of a new board, it may be desirable > to not reset any IP block, for ease of debugging. This patch adds a > kernel command line parameter, 'hwmod_no_setup_reset', that prevents > the OMAP hwmod code from resetting any IP block during init. > > 1. Nayak, Rajendra. _[PATCH 7/7] 4460sdp/blaze/panda: hwmod: Prevent > gpio1 reset during hwmod init_. 1 July 2011. E-mail to the > linux-omap@vger.kernel.org mailing list. Retrieved from > http://www.mail-archive.com/linux-omap@vger.kernel.org/msg51992.html > > 2. Buesch, Michael. _Nokia n810 LCD (MIPID/blizzard) on 2.6.38_. 28 > Feb 2011. E-mail to the linux-omap@vger.kernel.org mailing list. > Retrieved from http://www.spinics.net/lists/linux-omap/msg47277.html Also related is the gptimer12 on secure omaps as reported by Aaro. > + hwmod_no_setup_reset > + [OMAP] During kernel initialization, > + prevent the subarchitecture code from resetting > + IP blocks before the driver loads. Useful for > + initial bring-up of boards which require some > + bootloader configuration to be retained on GPIO or > + other IP blocks. > + How about just make it hwmod_reset=1 with 0 being the default value for now? Regards, Tony