Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752101AbbBMDIi (ORCPT ); Thu, 12 Feb 2015 22:08:38 -0500 Received: from mail-ob0-f175.google.com ([209.85.214.175]:57308 "EHLO mail-ob0-f175.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751594AbbBMDIg (ORCPT ); Thu, 12 Feb 2015 22:08:36 -0500 Message-ID: <54dd6ab3.6a5e3c0a.3c85.59de@mx.google.com> X-Google-Original-Message-ID: 2e2cfc2e-8c4e-48c4-a758-3ac8717c196c@gmail.com> Date: Thu, 12 Feb 2015 20:58:49 -0600 Subject: Re: [PATCH RFC v9 01/20] clk: divider: Correct parent clk round rate if no bestdiv is normally found In-Reply-To: <20150213025825.GA30014@victor> References: <1423720903-24806-1-git-send-email-Ying.Liu@freescale.com> <1423720903-24806-2-git-send-email-Ying.Liu@freescale.com> <20150212093356.GR12209@pengutronix.de> <20150212103944.GA1290@victor> <20150212122405.GW12209@pengutronix.de> <20150212125646.GT8656@n2100.arm.linux.org.uk> <20150212134131.GX12209@pengutronix.de> <20150212140625.GA32487@victor> <20150213025825.GA30014@victor> From: Travis To: Liu Ying Cc: andy.yan@rock-chips.com, a.hajda@samsung.com, Tomi Valkeinen , Sascha Hauer , linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, kernel@pengutronix.de, stefan.wahren@i2se.com, mturquette@linaro.org, linux-arm-kernel@lists.infradead.org, sboyd@codeaurora.org, dri-devel@lists.freedesktop.org, Russell King - ARM Linux MIME-Version: 1.0 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-Transfer-Encoding: 8bit X-MIME-Autoconverted: from base64 to 8bit by nfs id t1D38iUi000634 Content-Length: 7585 Lines: 120 Travis liked your message with Boxer for Android. On Feb 12, 2015 8:58 PM, Liu Ying wrote: > > On Thu, Feb 12, 2015 at 10:06:27PM +0800, Liu Ying wrote: > > On Thu, Feb 12, 2015 at 02:41:31PM +0100, Sascha Hauer wrote: > > > On Thu, Feb 12, 2015 at 12:56:46PM +0000, Russell King - ARM Linux wrote: > > > > On Thu, Feb 12, 2015 at 01:24:05PM +0100, Sascha Hauer wrote: > > > > > On Thu, Feb 12, 2015 at 06:39:45PM +0800, Liu Ying wrote: > > > > > > On Thu, Feb 12, 2015 at 10:33:56AM +0100, Sascha Hauer wrote: > > > > > > > On Thu, Feb 12, 2015 at 02:01:24PM +0800, Liu Ying wrote: > > > > > > > > If no best divider is normally found, we will try to use the maximum divider. > > > > > > > > We should not set the parent clock rate to be 1Hz by force for being rounded. > > > > > > > > Instead, we should take the maximum divider as a base and calculate a correct > > > > > > > > parent clock rate for being rounded. > > > > > > > > > > > > > > Please add an explanation why you think the current code is wrong and > > > > > > > what this actually fixes, maybe an example? > > > > > > > > > > > > The MIPI DSI panel's pixel clock rate is 26.4MHz and it's derived from PLL5 on > > > > > > the MX6DL SabreSD board. > > > > > > > > > > > > These are the clock tree summaries with or without the patch applied: > > > > > > 1) With the patch applied: > > > > > > pll5_bypass_src                       1            1    24000000          0 0 > > > > > >    pll5                               1            1   844800048          0 0 > > > > > >       pll5_bypass                     1            1   844800048          0 0 > > > > > >          pll5_video                   1            1   844800048          0 0 > > > > > >             pll5_post_div             1            1   211200012          0 0 > > > > > >                pll5_video_div           1            1   211200012        0 0 > > > > > >                   ipu1_di0_pre_sel           1            1   211200012   0 0 > > > > > >                      ipu1_di0_pre           1            1    26400002    0 0 > > > > > >                         ipu1_di0_sel           1            1    26400002 0 0 > > > > > >                            ipu1_di0           1            1    26400002  0 0 > > > > > > > > > > > > 2) Without the patch applied: > > > > > > pll5_bypass_src                       1            1    24000000          0 0 > > > > > >    pll5                               1            1   648000000          0 0 > > > > > >       pll5_bypass                     1            1   648000000          0 0 > > > > > >          pll5_video                   1            1   648000000          0 0 > > > > > >             pll5_post_div             1            1   162000000          0 0 > > > > > >                pll5_video_div           1            1    40500000        0 0 > > > > > >                   ipu1_di0_pre_sel           1            1    40500000   0 0 > > > > > >                      ipu1_di0_pre           1            1    20250000    0 0 > > > > > >                         ipu1_di0_sel           1            1    20250000 0 0 > > > > > >                            ipu1_di0           1            1    20250000  0 0 > > > > > > > > > > This seems to be broken since: > > > > > > > > > > | commit b11d282dbea27db1788893115dfca8a7856bf205 > > > > > | Author: Tomi Valkeinen > > > > > | Date:   Thu Feb 13 12:03:59 2014 +0200 > > > > > | > > > > > |     clk: divider: fix rate calculation for fractional rates > > > > > > > > > > This patch fixed a case when clk_set_rate(clk_round_rate(rate)) resulted > > > > > in a lower frequency than clk_round_rate(rate) returned. > > > > > > > > > > Since then the MULT_ROUND_UP in clk_divider_bestdiv() is inconsistent to > > > > > the rest of the divider. Maybe this should be a simple rate * i now, but > > > > > I'm unsure what side effects this has. > > > > > > > > > > I think your patch only fixes the behaviour in your case by accident, > > > > > it's not a correct fix for this issue. > > > > > > > > Well, it's defined that: > > > > > > > > new_rate = clk_round_rate(clk, rate); > > > > > > > > returns the rate which you would get if you did: > > > > > > > > clk_set_rate(clk, rate); > > > > new_rate = clk_get_rate(clk); > > > > > > > > The reasoning here is that clk_round_rate() gives you a way to query what > > > > rate you would get if you were to ask for the rate to be set, without > > > > effecting a change in the hardware. > > > > > > > > The idea that you should call clk_round_rate() first before clk_set_rate() > > > > and pass the returned rounded rate into clk_set_rate() is really idiotic > > > > given that.  Please don't do it, and please remove code which does it, and > > > > in review comment on it.  Thanks. > > > > > > Tomis patch is based on the assumption that clk_set_rate(clk_round_rate(rate)) > > > is equal to clk_round_rate(rate). So when this assumption is wrong then > > > it should simply be reverted. > > > So Liu, could you test if reverting Tomis patch fixes your problem? > > > > Yes, I'll test tomorrow when I have access to my board. > > Tomi's patch cannot be reverted directly because of conflicts with the later > patches.  So, I revert all the clock divider driver patches on top of that. > And, yes, after reverting Tomi's patch, I may get the correct 26.4MHz pixel > clock rate. > > Regards, > Liu Ying > > > > > Regards, > > Liu Ying > > > > > > > > Sascha > > > > > > -- > > > Pengutronix e.K.                           |                             | > > > Industrial Linux Solutions                 | http://www.pengutronix.de/  | > > > Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    | > > > Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 | > > _______________________________________________ > > dri-devel mailing list > > dri-devel@lists.freedesktop.org > > http://lists.freedesktop.org/mailman/listinfo/dri-devel > -- > 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/ ????{.n?+???????+%?????ݶ??w??{.n?+????{??G?????{ay?ʇڙ?,j??f???h?????????z_??(?階?ݢj"???m??????G????????????&???~???iO???z??v?^?m???? ????????I?