From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752838Ab1IUQOL (ORCPT ); Wed, 21 Sep 2011 12:14:11 -0400 Received: from mho-03-ewr.mailhop.org ([204.13.248.66]:33422 "EHLO mho-01-ewr.mailhop.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752436Ab1IUQOJ (ORCPT ); Wed, 21 Sep 2011 12:14:09 -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: U2FsdGVkX19JPr89rOi+oGyVYylJs52B Date: Wed, 21 Sep 2011 09:14:06 -0700 From: Tony Lindgren To: Ohad Ben-Cohen Cc: linux-omap@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Arnd Bergmann Subject: Re: [PATCH 04/10] hwspinlock/core/omap: fix id issues on multiple hwspinlock devices Message-ID: <20110921161406.GF2937@atomide.com> References: <1315846025-11453-1-git-send-email-ohad@wizery.com> <1315846025-11453-5-git-send-email-ohad@wizery.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1315846025-11453-5-git-send-email-ohad@wizery.com> 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 * Ohad Ben-Cohen [110912 09:14]: > hwspinlock devices provide system-wide hardware locks that are used > by remote processors that have no other way to achieve synchronization. > > For that to work, each physical lock must have a system-wide unique id > number that all processors are familiar with, otherwise they can't > possibly assume they're using the same hardware lock. > > Usually SoCs have a single hwspinlock device, which provides several > hwspinlocks, and in this case, they can be trivially numbered 0 to > (num-of-locks - 1). > > In case boards have several hwspinlocks devices (each of which > providing numerous hardware spinlocks) a different base id should be > used for each hwspinlock device (they can't all use 0 as a starting > id!). > > While this is certainly not common, it's just plain wrong to just > silently use 0 as a base id whenever the hwspinlock driver is probed. > > This patch provides a hwspinlock_pdata structure, that boards can use > to set a different base id for each of the hwspinlock devices they may > have, and demonstrates how to use it with the omap hwspinlock driver > (ultimately it will be DT which will supply this base_id information). > > While we're at it, make sure the hwspinlock core prints an explicit > error message in case an hwspinlock is registered with an id number > that already exists; this will help users catch such base id issues. > > Reported-by: Arnd Bergmann > Signed-off-by: Ohad Ben-Cohen Acked-by: Tony Lindgren