From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753069AbcB2BPT (ORCPT ); Sun, 28 Feb 2016 20:15:19 -0500 Received: from lucky1.263xmail.com ([211.157.147.132]:60495 "EHLO lucky1.263xmail.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751942AbcB2BPS (ORCPT ); Sun, 28 Feb 2016 20:15:18 -0500 X-263anti-spam: KSV:0; X-MAIL-GRAY: 1 X-MAIL-DELIVERY: 0 X-KSVirus-check: 0 X-ABS-CHECKED: 4 X-ADDR-CHECKED: 0 X-RL-SENDER: shawn.lin@rock-chips.com X-FST-TO: linux-kernel@vger.kernel.org X-SENDER-IP: 58.22.7.114 X-LOGIN-NAME: shawn.lin@rock-chips.com X-UNIQUE-TAG: X-DNS-TYPE: 0 Subject: Re: [PATCH v2] clk: check the actual phase if get_phase is provided To: Stephen Boyd References: <1455759499-9622-1-git-send-email-shawn.lin@rock-chips.com> <20160225231458.GH28849@codeaurora.org> <56CFA8B4.7070600@rock-chips.com> <20160227001042.GC28849@codeaurora.org> Cc: shawn.lin@rock-chips.com, Michael Turquette , linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org From: Shawn Lin Message-ID: <56D39B8C.9030008@rock-chips.com> Date: Mon, 29 Feb 2016 09:14:52 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.3; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 MIME-Version: 1.0 In-Reply-To: <20160227001042.GC28849@codeaurora.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2016/2/27 8:10, Stephen Boyd wrote: > On 02/26, Shawn Lin wrote: >> On 2016/2/26 7:14, Stephen Boyd wrote: >>> On 02/18, Shawn Lin wrote: >>>> set_phase does sanity checking of degree and ask sub-driver >> >> [...] >> >>>> already there. >>>> >>>> Signed-off-by: Shawn Lin >>>> >>>> --- >>> >>> Knee jerk reaction is why does the provider code set a phase that >>> isn't requested? Do we need some sort of clk_round_phase() API >>> that parallels clk_round_rate() so that drivers know what phase >>> they're going to get? Or do drivers not care what phase they get >>> when they call clk_set_phase()? >> >> Hi Stephen, >> >> drivers should care what phase they get when calling clk_set_phase(i.e >> the drivers setting phase to do tuning work should know what the actual >> degrees is, which is important for them to decide the sample window >> algorithm). >> >> By looking into the two drivers who use set_phase/get_phase pair >> currently, they actually both don'e care what the actual degrees when >> they call clk_set_phase. I think that is because the drivers are used >> for specific platform which support 0~360 implicitly. But the situation >> is NOT always right for cross-platform drivers. So add some sort of >> round_phase API is probably sane ? >> > > Do you have such a platform or driver though? I'd rather not do > anything unless we actually need to. Currently no, but we going to have one soon in this year which supports 10°, 20°, 30°,... 360°(each 10° a step, totally 36 steps). So I look into phase stuff in advance and send a RFC patch to discuss the practicability before I actually writing driver code. I have no idea whether we need it. Or maybe we can just do some tricks inside current ->set_phase/get_phase call back to meet the requirment. Otherwise， I'd rather not add New API either. > -- Best Regards Shawn Lin