From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933561AbeCEJHB (ORCPT ); Mon, 5 Mar 2018 04:07:01 -0500 Received: from mailout1.w1.samsung.com ([210.118.77.11]:42193 "EHLO mailout1.w1.samsung.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932868AbeCEJGv (ORCPT ); Mon, 5 Mar 2018 04:06:51 -0500 DKIM-Filter: OpenDKIM Filter v2.11.0 mailout1.w1.samsung.com 20180305090648euoutp01e2d2df4435c73e34831d0dfd1e525cd2~Y_vYOTFok2892228922euoutp01F X-AuditID: cbfec7f2-5ffe19c000011644-bc-5a9d08a70e92 MIME-version: 1.0 Content-type: text/plain; charset="utf-8"; format="flowed" Subject: Re: [PATCH v2 4/8] clk: migrate the count of orphaned clocks at init From: Marek Szyprowski To: Jerome Brunet , Michael Turquette , Stephen Boyd Cc: linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org, Stephen Boyd , Shawn Guo , Dong Aisheng , Krzysztof Kozlowski Message-id: <40e6c987-633c-b806-02e8-5299187bbcf0@samsung.com> Date: Mon, 05 Mar 2018 10:06:45 +0100 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.6.0 In-reply-to: <7c9b0ac1-582c-9b25-4d62-844667e80507@samsung.com> Content-transfer-encoding: 8bit Content-language: en-US X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFprFKsWRmVeSWpSXmKPExsWy7djPc7rLOeZGGXyfZGjxZeouZos3j44w W5w/v4Hd4mPPPVaLy7vmsFlcPOVq8eNMN4vFv2sbWSxebBF34PR4f6OV3eNyXy+Tx6ZVnWwe G9/tYPL4vEkugDWKyyYlNSezLLVI3y6BK2PJLLmC1ToVZ1f+Ymlg7FTtYuTkkBAwkdjydSFr FyMXh5DACkaJWQe6oJzPjBKPD01kgana37GdCSKxjFHi/qu9YAleAUGJH5PvgdnMAlYSz/61 QnU/Z5R4dOYKI0hCWMBf4vTLl8wgNpuAoUTX2y42EFtEoEJiw78tbCANzAIXGSVed14AmsQB NNVO4vz8eBCTRUBV4veJLBBTVCBG4vUfN5BOTgF7iVnLj7BBrJWXOHjlOdQJ4hLNrTdZQCZK CFxmk/jU0s8G8YCLRNuTGVC2sMSr41vYIWwZic6Og0wQdr1E3/cjTBDNPYwSe1umQiWsJQ4f v8gKsYFPYtK26cwgB0kI8Ep0tAlBlHhIbFywBRpYjhJzlm8FKxcS+MQosepx0gRGuVlIwTUL KbhmIflhFpIfFjCyrGIUTy0tzk1PLTbMSy3XK07MLS7NS9dLzs/dxAhMMaf/Hf+0g/HrpaRD jAIcjEo8vDvy5kQJsSaWFVfmHmKU4GBWEuEt+wwU4k1JrKxKLcqPLyrNSS0+xCjNwaIkzhun URclJJCeWJKanZpakFoEk2Xi4JRqYAwM3H2/epc4J4e0A5PstiL3f+eW5qYqsO27mbpKslJS +NOfVhndV2XGefUZ0vUPy3d596q5/5q5li2sSOhm7NHvEvkxngdeizN/cxe1esPCn/91l9O/ v6v+v+RiL5VYwTpbJCtoop76FuZP++8Y/qqYuGPKEn+bw0vWBVt6BHqeztu4TX+FkRJLcUai oRZzUXEiAPv3dUwtAwAA X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFnrLLMWRmVeSWpSXmKPExsVy+t/xa7rLOeZGGTz/zGbxZeouZos3j44w W5w/v4Hd4mPPPVaLy7vmsFlcPOVq8eNMN4vFv2sbWSxebBF34PR4f6OV3eNyXy+Tx6ZVnWwe G9/tYPL4vEkugDWKyyYlNSezLLVI3y6BK2PJLLmC1ToVZ1f+Ymlg7FTtYuTkkBAwkdjfsZ2p i5GLQ0hgCaPE5oZrrCAJXgFBiR+T77GA2MwCZhJfXh5mhSh6ziix7cBDZpCEsICvxNv2NWwg NpuAoUTX2y4wW0SgQuLm9I/sEM0XGSX+HK+HaJ7HKNG57jpQggNog53E+fnxICaLgKrE7xNZ IOWiAjESUz9uBLuBU8BeYtbyI2wQY+QlDl55DnWPuERz602WCYwCs5CcOgvJqbOQtMxC0rKA kWUVo0hqaXFuem6xoV5xYm5xaV66XnJ+7iZGYCRsO/Zz8w7GSxuDDzEKcDAq8fAKFM6JEmJN LCuuzD3EKMHBrCTCW/YZKMSbklhZlVqUH19UmpNafIhRmoNFSZz3vEFllJBAemJJanZqakFq EUyWiYNTqoFRIL74u3da4FvD8D73mhdTfU9p6mht9GUV7Hqpy34pVinKsuzOkbsc60KEtswy bOs47nPv0cEzc3Pz7D5//vN0fqeW8tkZKoGnVxjIqNde4ZdUtXrCtdxr4hGf98+6dmVJss0+ nPqb/XKVrVjCcrVC66c7S9+zWXpKz9O+bH2jiml31eOktcuVWIozEg21mIuKEwElPb2xgAIA AA== X-CMS-MailID: 20180305090647eucas1p14c01d34dd2eef3eaab8752bf90591c4c X-Msg-Generator: CA CMS-TYPE: 201P X-CMS-RootMailID: 20180305090647eucas1p14c01d34dd2eef3eaab8752bf90591c4c X-RootMTR: 20180305090647eucas1p14c01d34dd2eef3eaab8752bf90591c4c References: <20180214134340.17242-1-jbrunet@baylibre.com> <20180214134340.17242-5-jbrunet@baylibre.com> <7c9b0ac1-582c-9b25-4d62-844667e80507@samsung.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi All, On 2018-02-15 13:55, Marek Szyprowski wrote: > Hi Jerome, > > On 2018-02-14 14:43, Jerome Brunet wrote: >> The orphan clocks reparents should migrate any existing count from the >> orphan clock to its new acestor clocks, otherwise we may have >> inconsistent counts in the tree and end-up with gated critical clocks >> >> Assuming we have two clocks, A and B. >> * Clock A has CLK_IS_CRITICAL flag set. >> * Clock B is an ancestor of A which can gate. Clock B gate is left >>    enabled by the bootloader. >> >> Step 1: Clock A is registered. Since it is a critical clock, it is >> enabled. The clock being still an orphan, no parent are enabled. >> >> Step 2: Clock B is registered and reparented to clock A (potentially >> through several other clocks). We are now in situation where the enable >> count of clock A is 1 while the enable count of its ancestors is 0, >> which >> is not good. >> >> Step 3: in lateinit, clk_disable_unused() is called, the enable_count of >> clock B being 0, clock B is gated and and critical clock A actually gets >> disabled. >> >> This situation was found while adding fdiv_clk gates to the meson8b >> platform.  These clocks parent clk81 critical clock, which is the mother >> of all peripheral clocks in this system. Because of the issue described >> here, the system is crashing when clk_disable_unused() is called. >> >> The situation is solved by reverting >> commit f8f8f1d04494 ("clk: Don't touch hardware when reparenting >> during registration"). >> To avoid breaking again the situation described in this commit >> description, enabling critical clock should be done before walking the >> orphan list. This way, a parent critical clock may not be accidentally >> disabled due to the CLK_OPS_PARENT_ENABLE mechanism. >> >> Fixes: f8f8f1d04494 ("clk: Don't touch hardware when reparenting >> during registration") >> Cc: Stephen Boyd >> Cc: Shawn Guo >> Cc: Dong Aisheng >> Signed-off-by: Jerome Brunet > > Tested-by: Marek Szyprowski > > This patch fixes kernel oops on Exynos5422-based boards (Odroid XU3/XU4) > mentioned in the following threads: > https://patchwork.kernel.org/patch/10185357/ > https://www.spinics.net/lists/linux-samsung-soc/msg61766.html Stephen, Michael: v4.16-rc4 is out today and this regression (which got merged on 22 Dec 2017) is still not fixed yet... Is there a chance to get it into final v4.16 release? >> --- >>   drivers/clk/clk.c | 37 +++++++++++++++++++++---------------- >>   1 file changed, 21 insertions(+), 16 deletions(-) >> >> diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c >> index a4b4e4d6df5e..cca05ea2c058 100644 >> --- a/drivers/clk/clk.c >> +++ b/drivers/clk/clk.c >> @@ -2969,23 +2969,38 @@ static int __clk_core_init(struct clk_core >> *core) >>           rate = 0; >>       core->rate = core->req_rate = rate; >>   +    /* >> +     * Enable CLK_IS_CRITICAL clocks so newly added critical clocks >> +     * don't get accidentally disabled when walking the orphan tree and >> +     * reparenting clocks >> +     */ >> +    if (core->flags & CLK_IS_CRITICAL) { >> +        unsigned long flags; >> + >> +        clk_core_prepare(core); >> + >> +        flags = clk_enable_lock(); >> +        clk_core_enable(core); >> +        clk_enable_unlock(flags); >> +    } >> + >>       /* >>        * walk the list of orphan clocks and reparent any that newly >> finds a >>        * parent. >>        */ >>       hlist_for_each_entry_safe(orphan, tmp2, &clk_orphan_list, >> child_node) { >>           struct clk_core *parent = __clk_init_parent(orphan); >> -        unsigned long flags; >>             /* >> -         * we could call __clk_set_parent, but that would result in a >> -         * redundant call to the .set_rate op, if it exists >> +         * We need to use __clk_set_parent_before() and _after() to >> +         * to properly migrate any prepare/enable count of the orphan >> +         * clock. This is important for CLK_IS_CRITICAL clocks, which >> +         * are enabled during init but might not have a parent yet. >>            */ >>           if (parent) { >>               /* update the clk tree topology */ >> -            flags = clk_enable_lock(); >> -            clk_reparent(orphan, parent); >> -            clk_enable_unlock(flags); >> +            __clk_set_parent_before(orphan, parent); >> +            __clk_set_parent_after(orphan, parent, NULL); >>               __clk_recalc_accuracies(orphan); >>               __clk_recalc_rates(orphan, 0); >>           } >> @@ -3002,16 +3017,6 @@ static int __clk_core_init(struct clk_core *core) >>       if (core->ops->init) >>           core->ops->init(core->hw); >>   -    if (core->flags & CLK_IS_CRITICAL) { >> -        unsigned long flags; >> - >> -        clk_core_prepare(core); >> - >> -        flags = clk_enable_lock(); >> -        clk_core_enable(core); >> -        clk_enable_unlock(flags); >> -    } >> - >>       kref_init(&core->ref); >>   out: >>       clk_pm_runtime_put(core); > Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland