linux-kernel - Re: [PATCH] clk: mvebu: armada-37xx-periph: Fix initialization for cpu clocks

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Date:   Thu, 14 Mar 2019 14:15:41 +0200
From:   Ilias Apalodimas <ilias.apalodimas@...aro.org>
To:     Gregory CLEMENT <gregory.clement@...tlin.com>
Cc:     Stephen Boyd <sboyd@...eaurora.org>,
        Mike Turquette <mturquette@...libre.com>,
        linux-clk@...r.kernel.org, linux-kernel@...r.kernel.org,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        linux-pm@...r.kernel.org,
        Christian Neubert <christian.neubert.86@...il.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Jason Cooper <jason@...edaemon.net>,
        Andrew Lunn <andrew@...n.ch>,
        Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        linux-arm-kernel@...ts.infradead.org,
        Antoine Tenart <antoine.tenart@...tlin.com>,
        Miquèl Raynal <miquel.raynal@...tlin.com>,
        Maxime Chevallier <maxime.chevallier@...tlin.com>,
        stable@...r.kernel.org
Subject: Re: [PATCH] clk: mvebu: armada-37xx-periph: Fix initialization for
 cpu clocks

Hi Gregory, 
> The clock parenting was not setup properly when DVFS was enabled. It was
> expected that the same clock source was used with and without DVFS which
> was not the case.
> 
> This patch fixes this issue, allowing to make the cpufreq support work
> when the CPU clocks source are not the default ones.
> 
> Fixes: 92ce45fb875d ("cpufreq: Add DVFS support for Armada 37xx")
> Cc: <stable@...r.kernel.org>
> Reported-by: Christian Neubert <christian.neubert.86@...il.com>
> Reported-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>
> Signed-off-by: Gregory CLEMENT <gregory.clement@...tlin.com>
> ---
>  drivers/clk/mvebu/armada-37xx-periph.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/drivers/clk/mvebu/armada-37xx-periph.c b/drivers/clk/mvebu/armada-37xx-periph.c
> index 1f1cff428d78..26ed3c18a239 100644
> --- a/drivers/clk/mvebu/armada-37xx-periph.c
> +++ b/drivers/clk/mvebu/armada-37xx-periph.c
> @@ -671,6 +671,17 @@ static int armada_3700_add_composite_clk(const struct clk_periph_data *data,
>  		map = syscon_regmap_lookup_by_compatible(
>  				"marvell,armada-3700-nb-pm");
>  		pmcpu_clk->nb_pm_base = map;
> +
> +		/*
> +		 * Use the same parent when DVFS is enabled that the
> +		 * default parent received at boot time. When this
> +		 * function is called, DVFS is not enabled yet, so we
> +		 * get the default parent and we can set the parent
> +		 * for DVFS.
> +		 */
> +		if (clk_pm_cpu_set_parent(muxrate_hw,
> +					  clk_pm_cpu_get_parent(muxrate_hw)))
> +			dev_warn(dev, "Failed to setup default parent clock for DVFS\n");
>  	}
>  
>  	*hw = clk_hw_register_composite(dev, data->name, data->parent_names,
> -- 
> 2.20.1
> 
Applied this and selected only

CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE=y
CONFIG_CPU_FREQ_GOV_PERFORMANCE=y
CONFIG_CPU_FREQ_GOV_POWERSAVE=y

After changing the governor from 'powersave' to 'performance' the board
completely froze (i even lost access to the serial port)

Cheers
/Ilias