Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751423AbdFGPJV (ORCPT ); Wed, 7 Jun 2017 11:09:21 -0400 Received: from mail.free-electrons.com ([62.4.15.54]:48555 "EHLO mail.free-electrons.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750975AbdFGPJU (ORCPT ); Wed, 7 Jun 2017 11:09:20 -0400 Date: Wed, 7 Jun 2017 17:09:08 +0200 From: Alexandre Belloni To: Daniel Lezcano Cc: Nicolas Ferre , Boris Brezillon , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Thomas Gleixner Subject: Re: [PATCH 46/58] clocksource/drivers: Add a new driver for the Atmel ARM TC blocks Message-ID: <20170607150908.kytgtzwgjjnxtsp3@piout.net> References: <20170530215139.9983-1-alexandre.belloni@free-electrons.com> <20170530215139.9983-47-alexandre.belloni@free-electrons.com> <20170606152104.GC2345@mai> <20170606180559.pkrr7ux2qqnmsd6y@piout.net> <20170607141735.GH2345@mai> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170607141735.GH2345@mai> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1545 Lines: 41 On 07/06/2017 at 16:17:35 +0200, Daniel Lezcano wrote: > > > > This driver uses regmap and syscon to be able to probe early in the boot > > > > and avoid having to switch on the TCB clocksource later. Using regmap also > > > > means that unused TCB channels may be used by other drivers (PWM for > > > > example). > > > > > > Can you give more details, I fail to understand how regmap and syscon help to > > > probe sooner than timer_init()? > > > > > > Because before that, the tcb driver relied on atmel_tclib to share the > > TCBs and it happened way too late, at arch_initcall() time. > > So is it still necesary to use regmap? I would like to take the opportunity to > move the init routine to the common init routine if possible: > > https://patchwork.kernel.org/patch/9768845/ > It is still necessary because we want to be able to share the timer between multiple drivers. For example, you can have the clocksource on channel 0, clockevent on channel 1 and a pwm on channel 2 > > > Can you explain why we have two clocks here? > > > > > > > Each channel have its clock, I can add a comment if you want. > > I don't understand. Why do we have two clocks? > > One channel is driven by one clock and the second one takes the overflow signal > from the first one, so no second clock is involved there, no? > Those are the peripheral clocks, they are not used by the counters but used to be able to read/write the registers. -- Alexandre Belloni, Free Electrons Embedded Linux and Kernel engineering http://free-electrons.com