Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754550Ab3C0KDX (ORCPT ); Wed, 27 Mar 2013 06:03:23 -0400 Received: from mail-vc0-f177.google.com ([209.85.220.177]:59747 "EHLO mail-vc0-f177.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753985Ab3C0KDW (ORCPT ); Wed, 27 Mar 2013 06:03:22 -0400 MIME-Version: 1.0 In-Reply-To: References: <1364368183-24420-1-git-send-email-mturquette@linaro.org> Date: Wed, 27 Mar 2013 11:03:21 +0100 Message-ID: Subject: Re: [PATCH v4] clk: allow reentrant calls into the clk framework From: Ulf Hansson To: Viresh Kumar Cc: Thomas Gleixner , Mike Turquette , linaro-kernel@lists.linaro.org, patches@linaro.org, linux-kernel@vger.kernel.org, Laurent Pinchart , David Brown , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1961 Lines: 51 On 27 March 2013 10:55, Viresh Kumar wrote: > On 27 March 2013 15:10, Thomas Gleixner wrote: >> On Wed, 27 Mar 2013, Mike Turquette wrote: >> >>> Reentrancy into the clock framework from the clk.h api is necessary >>> for clocks that are prepared and unprepared via i2c_transfer (which >>> includes many PMICs and discrete audio chips) as well as for several >>> other use cases. >> >> That explanation sucks. >> >> Why does an i2c clock need reentrancy? Just because it's i2c or what? > > I am noway connected to this development but was just going through > your mail and i think i might know the answer why is this required. > > Consider an example where an external chip has clock controller and has > bits which can be programmed to enable/disable clock. And this chip is > connected via spi/i2c to SoC. > > clk_prepare(peripheral on external chip) > -> i2c_xfer(to write to external chips register) > -> clk_enable(i2c controller) > ->controller-xfer-routine.. and finally we enable clk here... > > > Sorry if i am on the wrong side :) I agree with you Viresh. I guess Mike should update the commit message. I would also like add another reason to why this is needed. For some clks you would like to do pinctrl operations from a clk hw. But since a pinctrl driver likely requires a clk to be prepared|enabled, we run into a clk reentrant issue. Kind regards Ulf Hansson > > -- > viresh > -- > 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/ -- 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/