Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751248AbaFLW4R (ORCPT ); Thu, 12 Jun 2014 18:56:17 -0400 Received: from gw-1.arm.linux.org.uk ([78.32.30.217]:56349 "EHLO pandora.arm.linux.org.uk" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750811AbaFLW4Q (ORCPT ); Thu, 12 Jun 2014 18:56:16 -0400 Date: Thu, 12 Jun 2014 23:55:54 +0100 From: Russell King - ARM Linux To: Stephen Warren Cc: Peter De Schrijver , Paul Gortmaker , Daniel Lezcano , Thomas Gleixner , Thierry Reding , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-tegra@vger.kernel.org Subject: Re: [PATCH 0/3] Use Tegra's microsecond counter for udelay() Message-ID: <20140612225553.GO23430@n2100.arm.linux.org.uk> References: <1402588713-18766-1-git-send-email-pdeschrijver@nvidia.com> <539A01B4.3050503@wwwdotorg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <539A01B4.3050503@wwwdotorg.org> User-Agent: Mutt/1.5.19 (2009-01-05) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jun 12, 2014 at 01:38:28PM -0600, Stephen Warren wrote: > On 06/12/2014 09:58 AM, Peter De Schrijver wrote: > > This patchset introduces support for Tegra's microsecond counter as the > > udelay() timer. This is useful on Tegra SoCs which do not have an arch timer > > such as Tegra20 and Tegra30. Using the microsecond counter instead of a delay > > based loop avoids potential problems during cpu frequency changes. > > > > The set consists of 3 patches: > > > > Patch 1 introduces a new call which is used by the ARM architecture delay > > timer code to prevent changing the delay timer after calibration is finished > > and thus can be in use. > > > > Patch 2 adds logic to choose the delay timer with the highest resolution. This > > allows the same registration code to be used on all Tegra SoCs and yet use the > > higher resolution arch timer when available (eg on Tegra114 or Tegra124). > > > > Patch 3 adds the actual delay timer code. > > > > Patch set has been verified on ventana (Tegra20), beaver (Tegra30), > > dalmore (Tegra114) and jetson TK1 (Tegra124). > > Russell, Paul, do patches 1 and 2 look good to you? If so, if you can > ack them, I'd be happy to queue this series in the Tegra git tree. If > that doesn't work for you, please let me know who will apply these > patches. Thanks. When I saw them, I did have a question in the back of my mind about the interlocking - whether we should just mandate that these are always registered before delay calibration. Then I remember the mess that platforms made of the sched_clock() stuff. So, I don't see any other way to ensure that platforms do the right thing other than providing that kind of stick... so I guess we'll have to have them. Acked-by: Russell King -- FTTC broadband for 0.8mile line: now at 9.7Mbps down 460kbps up... slowly improving, and getting towards what was expected from it. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/