From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753897AbbJZMmh (ORCPT ); Mon, 26 Oct 2015 08:42:37 -0400 Received: from mail-pa0-f51.google.com ([209.85.220.51]:35188 "EHLO mail-pa0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753316AbbJZMmf convert rfc822-to-8bit (ORCPT ); Mon, 26 Oct 2015 08:42:35 -0400 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8BIT To: "Jon Medhurst (Tixy)" , "Viresh Kumar" , "Sudeep Holla" , "Rafael J. Wysocki" From: Michael Turquette In-Reply-To: <1445421333.2916.13.camel@linaro.org> Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org References: <1445421333.2916.13.camel@linaro.org> Message-ID: <20151026124228.22783.64941@quantum> User-Agent: alot/0.3.6 Subject: Re: [PATCH v2] cpufreq: arm_big_little: fix frequency check when bL switcher is active Date: Mon, 26 Oct 2015 05:42:28 -0700 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Quoting Jon Medhurst (Tixy) (2015-10-21 02:55:33) > The check for correct frequency being set in bL_cpufreq_set_rate is > broken when the big.LITTLE switcher is active, for two reasons. > > 1. The 'new_rate' variable gets overwritten before the test by the > code calculating the frequency of the old cluster. > > 2. The frequency returned by bL_cpufreq_get_rate will be the virtual > frequency, not the actual one the intended version of new_rate contains. > > This means the function always returns an error causing an endless > stream of: "cpufreq: __target_index: Failed to change cpu frequency: -5" > > As the intent is to check for errors that clk_set_rate doesn't report > lets move the check to immediately after that and directly use > clk_get_rate, rather than the arm_big_little helpers which only confuse > matters. Also, update the comment to be hopefully clearer about the > purpose of the code. > > Fixes: 0a95e630b49a ("cpufreq: arm_big_little: check if the frequency is set correctly") > > Signed-off-by: Jon Medhurst > Acked-by: Sudeep Holla Reviewed-by: Michael Turquette Fixing exception paths for clk_change_rate is on the TODO list. Regards, Mike > --- > > Changes since V1: > - Check rate using clk_get_rate rather than disabling check when bL > switcher active > > Sudeep, I added your Ack from the last comment on the previous patch. > This final patch differs from what was discussed only in the commit > message and in source comment which is hopefully more clear and is > also satisfactory. > > I've also added Michael Turquette's correct email to the CC this time, > rather than his old Linaro address which was bouncing. > > drivers/cpufreq/arm_big_little.c | 22 +++++++++++++--------- > 1 file changed, 13 insertions(+), 9 deletions(-) > > diff --git a/drivers/cpufreq/arm_big_little.c b/drivers/cpufreq/arm_big_little.c > index f1e42f8..c5d256c 100644 > --- a/drivers/cpufreq/arm_big_little.c > +++ b/drivers/cpufreq/arm_big_little.c > @@ -149,6 +149,19 @@ bL_cpufreq_set_rate(u32 cpu, u32 old_cluster, u32 new_cluster, u32 rate) > __func__, cpu, old_cluster, new_cluster, new_rate); > > ret = clk_set_rate(clk[new_cluster], new_rate * 1000); > + if (!ret) { > + /* > + * FIXME: clk_set_rate hasn't returned an error here however it > + * may be that clk_change_rate failed due to hardware or > + * firmware issues and wasn't able to report that due to the > + * current design of the clk core layer. To work around this > + * problem we will read back the clock rate and check it is > + * correct. This needs to be removed once clk core is fixed. > + */ > + if (clk_get_rate(clk[new_cluster]) != new_rate * 1000) > + ret = -EIO; > + } > + > if (WARN_ON(ret)) { > pr_err("clk_set_rate failed: %d, new cluster: %d\n", ret, > new_cluster); > @@ -189,15 +202,6 @@ bL_cpufreq_set_rate(u32 cpu, u32 old_cluster, u32 new_cluster, u32 rate) > mutex_unlock(&cluster_lock[old_cluster]); > } > > - /* > - * FIXME: clk_set_rate has to handle the case where clk_change_rate > - * can fail due to hardware or firmware issues. Until the clk core > - * layer is fixed, we can check here. In most of the cases we will > - * be reading only the cached value anyway. This needs to be removed > - * once clk core is fixed. > - */ > - if (bL_cpufreq_get_rate(cpu) != new_rate) > - return -EIO; > return 0; > } > > -- > 2.1.4 > > >