Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758884Ab3GRLz2 (ORCPT ); Thu, 18 Jul 2013 07:55:28 -0400 Received: from mail-ie0-f173.google.com ([209.85.223.173]:34909 "EHLO mail-ie0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757126Ab3GRLz1 (ORCPT ); Thu, 18 Jul 2013 07:55:27 -0400 MIME-Version: 1.0 In-Reply-To: <20130718110201.GB29153@e106331-lin.cambridge.arm.com> References: <1372943292-6960-1-git-send-email-jonas.jensen@gmail.com> <1374067396-30155-1-git-send-email-jonas.jensen@gmail.com> <20130718095035.GA29153@e106331-lin.cambridge.arm.com> <20130718110201.GB29153@e106331-lin.cambridge.arm.com> Date: Thu, 18 Jul 2013 13:55:26 +0200 Message-ID: Subject: Re: [PATCH v3] clk: add MOXA ART SoCs clock driver From: Jonas Jensen To: Mark Rutland Cc: "linux-arm-kernel@lists.infradead.org" , "arm@kernel.org" , "mturquette@linaro.org" , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1592 Lines: 44 On 18 July 2013 13:02, Mark Rutland wrote: > Ok. I'm just concerned that the linkage isn't explicit or obvious. > This does leave apb-clock completely dependent on core-clock, and unless > I've missed something there's no linkage between the two described in > the dt. I can add a description in the core-clock binding and also for apb-clock pointing out that it's set from core-clock. > How does core-clock physically relate to apb-clock? Does it feed or is > it fed by apb-clock? apb-clock is entirely a DT construct used by drivers to get the fixed rate 48MHz. It's not fed by core-clock more than what happens in probe. For UC-7112-LX, drivers using apb-clock are: clocksource, MMC, watchdog Because clocksource relies on apb-clock, a successful probe of core-clock is critical. Commonly, drivers look up the apb-clock node and call clk_get_rate. > Are we always guaranteed to have core-clock if we have apb-clock, and is > it part of the same block in hardware? If so we could describe the > amalgamation as a provider with two clock outputs, with core-clock's > registers for configuration at probe-time. Yes, as described above, there can not be a apb-clock without core-clock. I think drivers could find and use core-clock instead. Maybe the abstraction of apb-clock is unnecessary? Best regards, Jonas -- 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/