linux-kernel - Re: [PATCH] cpufreq: imx6q: Fix imx6sx low frequency support

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Date:   Thu, 31 Aug 2017 01:31:38 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Lucas Stach <l.stach@...gutronix.de>,
        Leonard Crestez <leonard.crestez@....com>
Cc:     Shawn Guo <shawnguo@...nel.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Anson Huang <Anson.Huang@....com>,
        Fabio Estevam <fabio.estevam@....com>,
        Dong Aisheng <aisheng.dong@....com>,
        Bai Ping <ping.bai@....com>, kernel@...gutronix.de,
        linux-pm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cpufreq: imx6q: Fix imx6sx low frequency support

On Monday, August 28, 2017 2:07:51 PM CEST Lucas Stach wrote:
> Am Montag, den 28.08.2017, 14:05 +0300 schrieb Leonard Crestez:
> > This patch contains the minimal changes required to support imx6sx OPP
> > of 198 Mhz. Without this patch cpufreq still reports success but the
> > frequency is not changed, the "arm" clock will still be at 396000000 in
> > clk_summary.
> > 
> > In order to do this PLL1 needs to be still kept enabled while changing
> > the ARM clock. This is a hardware requirement: when ARM_PODF is changed
> > in CCM we need to check the busy bit of CCM_CDHIPR bit 16 arm_podf_busy,
> > and this bit is sync with PLL1 clock, so if PLL1 NOT enabled, this
> > bit will never get clear.
> > 
> > Keep pll1_sys explicitly enabled until after the rate is change to deal
> > with this. Otherwise from the clk framework perspective pll1_sys is
> > unused and gets turned off.
> > 
> > Signed-off-by: Leonard Crestez <leonard.crestez@....com>
> 
> Reviewed-by: Lucas Stach <l.stach@...gutronix.de>

Patch applied, thanks!