From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932138AbaEGIiT (ORCPT ); Wed, 7 May 2014 04:38:19 -0400 Received: from mx08-00178001.pphosted.com ([91.207.212.93]:51050 "EHLO mx08-00178001.pphosted.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932069AbaEGIiR (ORCPT ); Wed, 7 May 2014 04:38:17 -0400 Message-ID: <5369F0D6.3080503@st.com> Date: Wed, 7 May 2014 10:37:42 +0200 From: Maxime Coquelin User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.5.0 MIME-Version: 1.0 To: Fabio Estevam , Cc: Fabio Estevam , , , , Subject: Re: [PATCH] clk: clk-divider: Fix infinite loop for table divider References: <1399408005-4209-1-git-send-email-festevam@gmail.com> In-Reply-To: <1399408005-4209-1-git-send-email-festevam@gmail.com> Content-Type: text/plain; charset="ISO-8859-1"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.129.6.55] X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:5.11.96,1.0.14,0.0.0000 definitions=2014-05-07_02:2014-05-06,2014-05-07,1970-01-01 signatures=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Fabio, On 05/06/2014 10:26 PM, Fabio Estevam wrote: > From: Fabio Estevam > > Since commit e7489693b3 (clk: divider: Optimize clk_divider_bestdiv loop) we > notice a system hang on mx6qboard. > > The cause for the hang is well explained by Sascha Hauer [1]: > > "This cannot work. _round_up_table is implemented like this: > > static int _round_up_table(const struct clk_div_table *table, int div) > { > const struct clk_div_table *clkt; > int up = _get_table_maxdiv(table); > > for (clkt = table; clkt->div; clkt++) { > if (clkt->div == div) > return clkt->div; > ... > } > ... > } > > Here when a table entry matches the input div this function will return > exactly the input div. This means _next_div() will always return the > same value and clk_divider_bestdiv() has an infinite loop: > > for (i = 1; i <= maxdiv; i = _next_div(divider, i)) { > ... > } > " > [1] http://marc.info/?l=linux-arm-kernel&m=139940658726253&w=2 > > Remove the 'return _round_up_table' so that the system can work normally again. > > Signed-off-by: Fabio Estevam > --- > drivers/clk/clk-divider.c | 2 -- > 1 file changed, 2 deletions(-) > > diff --git a/drivers/clk/clk-divider.c b/drivers/clk/clk-divider.c > index b3c8396..fc3e344 100644 > --- a/drivers/clk/clk-divider.c > +++ b/drivers/clk/clk-divider.c > @@ -246,8 +246,6 @@ static int _next_div(struct clk_divider *divider, int div) > > if (divider->flags & CLK_DIVIDER_POWER_OF_TWO) > return __roundup_pow_of_two(div); > - if (divider->table) > - return _round_up_table(divider->table, div); Couldn't we initialize "up" variable to INT_MAX in _round_up_table() as I just proposed in mail thread reporting the regression? See http://marc.info/?l=linux-arm-kernel&m=139945172905130&w=2 Regards, Maxime > > return div; > } >