Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755940Ab3GYMzV (ORCPT ); Thu, 25 Jul 2013 08:55:21 -0400 Received: from multi.imgtec.com ([194.200.65.239]:21411 "EHLO multi.imgtec.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755526Ab3GYMzR (ORCPT ); Thu, 25 Jul 2013 08:55:17 -0400 Message-ID: <51F1202D.9060403@imgtec.com> Date: Thu, 25 Jul 2013 13:55:09 +0100 From: James Hogan User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130625 Thunderbird/17.0.7 MIME-Version: 1.0 To: Sylwester Nawrocki CC: Mike Turquette , , Stephen Boyd , , Saravana Kannan , Doug Anderson , Sascha Hauer , Russell King , Viresh Kumar , Stephen Warren , Haojian Zhuang , Chao Xie , Arnd Bergmann , =?UTF-8?B?RW1pbGlvIEzDs3Bleg==?= , Gregory CLEMENT , Maxime Ripard , Prashant Gaikwad , Thierry Reding , Joseph Lo , Peter De Schrijver , "Pawel Moll" , Catalin Marinas , linux-samsung-soc Subject: Re: [PATCH v5 4/5] clk: add CLK_SET_RATE_NO_REPARENT flag References: <1371139562-305-1-git-send-email-james.hogan@imgtec.com> <1371139562-305-5-git-send-email-james.hogan@imgtec.com> <51F11B46.7010900@samsung.com> In-Reply-To: <51F11B46.7010900@samsung.com> X-Enigmail-Version: 1.5.1 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [192.168.154.65] X-SEF-Processed: 7_3_0_01192__2013_07_25_13_55_10 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2294 Lines: 59 Hi Sylwester On 25/07/13 13:34, Sylwester Nawrocki wrote: > On 06/13/2013 06:06 PM, James Hogan wrote: >> Add a CLK_SET_RATE_NO_REPARENT clock flag, which will prevent muxes >> being reparented during clk_set_rate. >> >> To avoid breaking existing platforms, all callers of clk_register_mux() >> are adjusted to pass the new flag. Platform maintainers are encouraged >> to remove the flag if they wish to allow mux reparenting on set_rate. > [..] >> Changes in v3: >> >> * rename/invert CLK_SET_RATE_REMUX to CLK_SET_RATE_NO_REPARENT and move >> to this new patch. >> * patch 3: add CLK_SET_RATE_NO_REPARENT flag to all callers of >> clk_register_mux. If you don't mind your clocks being reparented in >> response to set_rate please let me know and I'll drop the relevant >> portion of the patch. > > Why is this better to change current behaviour of the clock core > and modify all drivers instead of having, e.g. CLK_SET_RATE_REPARENT > set in drivers of hardware that supports clock re-parenting while > setting clock rate ? See this message from Mike Turquette which first suggested it: http://marc.info/?l=linux-kernel&m=136847508109344&w=2 > Is there intention to just have the automatic clock re-parenting > as a default feature in the common clock API ? Yes, that would be the result (except where explicitly disallowed). Unfortunately where such policy should ideally be defined is still up in the air. It's not a property of the hardware, but then it is arguably a property of the environment the bootloader has configured (like the stuff in the /chosen device tree node). Presuming that the usual reason not to reparent a mux is because other important clocks depend on it, the kernel might know enough to work out whether it's safe (unless of course there are other cores/threads in the SoC using the clock that Linux isn't aware of, which brings us back to it being a bootloader environment thing). > My apologies if this has already been answered, I haven't been > following this thread. No problem :) Cheers James -- 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/