Date: Fri, 21 Nov 2014 09:33:48 +0100
From: Lukasz Majewski <l.majewski@samsung.com>
To: Eduardo Valentin <edubezval@gmail.com>
Cc: Zhang Rui <rui.zhang@intel.com>,
        Ezequiel Garcia <ezequiel.garcia@free-electrons.com>,
        Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>,
        Linux PM list <linux-pm@vger.kernel.org>,
        Vincenzo Frascino <vincenzo.frascino@st.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        Lukasz Majewski <l.majewski@majess.pl>,
        Nobuhiro Iwamatsu <iwamatsu@nigauri.org>,
        Mikko Perttunen <mperttunen@nvidia.com>,
        Stephen Warren <swarren@wwwdotorg.org>,
        Thierry Reding <thierry.reding@gmail.com>,
        Alexandre Courbot <gnurou@gmail.com>, linux-tegra@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/8] thermal:cpu cooling:fix: Provide thermal core fixes
 with deferred probe for several drivers
Message-id: <20141121093348.456545c3@amdc2363>
In-reply-to: <20141120185420.GA26794@developer>
References: <1411547232-21493-1-git-send-email-l.majewski@samsung.com>
 <1415898165-27406-1-git-send-email-l.majewski@samsung.com>
 <20141120185420.GA26794@developer>
Organization: SPRC Poland
MIME-version: 1.0
Content-type: text/plain; charset=US-ASCII
Content-transfer-encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org

Hi Eduardo,

> Lukasz,
> 
> Thanks for the keeping this up. And apologize for late answer.

I've already posted v2 of this patch set (which consists of only one
patch :-) ).

Thanks to Thierry Reding's hint, I've realized that I don't need to add
code from patches 1-6 from v1.

Please instead review following patch:
"thermal:core:fix: Check return code of the ->get_max_state() callback"
https://patchwork.kernel.org/patch/5326991/


> 
> On Thu, Nov 13, 2014 at 06:02:37PM +0100, Lukasz Majewski wrote:
> > Presented fixes are a response for problem described below:
> > http://thread.gmane.org/gmane.linux.kernel/1793821/match=thermal+core+fix+initialize+max_state+variable+0
> > 
> > In short - it turned out that two trivial fixes (included in this
> > patch set) require support for deferred probe in thermal drivers.
> > 
> > This situation shows up when CPU frequency reduction is used as a
> > thermal cooling device for a thermal zone.
> > It happens that during initialization, the call to thermal probe
> > will be executed before cpufreq probe (it can be observed
> > at ./drivers/Makefile). In such a situation thermal will not be
> > properly configured until cpufreq policy is setup.
> > 
> > In the current code (without included fixes) there is a time window
> > in which thermal can try to use not configured cpufreq and possibly
> > crash the system.
> > 
> > 
> > Proposed solution was based on the code already available in the
> > imx_thermal.c file.
> > 
> > /db8500_thermal.c:                      -> NOT NEEDED
> > /intel_powerclamp.c:                    -> NOT NEEDED - INTEL (x86)
> > /intel_powerclamp.c:                    -> NOT NEEDED - INTEL (x86)
> > /ti-soc-thermal/ti-bandgap.c:           -> FIXED
> > [omap2plus_defconfig] /dove_thermal.c:                        ->
> > NOT NEEDED - CPU_COOLING NOT AVAILABLE [dove_defconfig]
> > /spear_thermal.c:                       -> FIXED
> > [spear3xx_defconfig] /samsung/exynos_tmu.c:                  -> NOT
> > NEEDED (nasty hack - will be reworked in later
> > patches) /imx_thermal.c:                         -> OK (deferred
> > probe already in place) /int340x_thermal/int3402_thermal.c:     ->
> > NOT NEEDED - ACPI x86 - Intel
> > specific /int340x_thermal/int3400_thermal.c:     -> NOT NEEDED -
> > ACPI x86 - Intel specific /tegra_soctherm.c:
> > -> FIXED  [tegra_defconfig] /kirkwood_thermal.c:
> > -> FIXED
> > [multi_v5_defconfig] /armada_thermal.c:                      ->
> > FIXED  [multi_v7_defconfig] /rcar_thermal.c:
> > -> FIXED
> > [shmobile_defconfig] /db8500_cpufreq_cooling.c:              -> OK
> > (deferred probe already in place)
> > [multi_v7_defconfig] /st/st_thermal_syscfg.c:                -> NOT
> > NEEDED (Those two are enabled by e.g.
> > ARMADA) /st/st_thermal_memmap.c:
> > 
> > 
> 
> 
> Instead of doing the same check on all drivers in the need for cpu
> cooling looks like a promiscuous solution. What if we do this check in
> cpu cooling itself and we propagate the error in callers code? 
> 
> From what I see, only exynos does not propagate the error. And we
> would need a tweak in the cpufreq-dt code. Something like the
> following (not tested):
> 
> diff --git a/drivers/cpufreq/cpufreq-dt.c
> b/drivers/cpufreq/cpufreq-dt.c index f657c57..f139247 100644
> --- a/drivers/cpufreq/cpufreq-dt.c
> +++ b/drivers/cpufreq/cpufreq-dt.c
> @@ -181,7 +181,6 @@ static int cpufreq_init(struct cpufreq_policy
> *policy) {
>  	struct cpufreq_dt_platform_data *pd;
>  	struct cpufreq_frequency_table *freq_table;
> -	struct thermal_cooling_device *cdev;
>  	struct device_node *np;
>  	struct private_data *priv;
>  	struct device *cpu_dev;
> @@ -264,20 +263,6 @@ static int cpufreq_init(struct cpufreq_policy
> *policy) goto out_free_priv;
>  	}
>  
> -	/*
> -	 * For now, just loading the cooling device;
> -	 * thermal DT code takes care of matching them.
> -	 */
> -	if (of_find_property(np, "#cooling-cells", NULL)) {
> -		cdev = of_cpufreq_cooling_register(np,
> cpu_present_mask);
> -		if (IS_ERR(cdev))
> -			dev_err(cpu_dev,
> -				"running cpufreq without cooling
> device: %ld\n",
> -				PTR_ERR(cdev));
> -		else
> -			priv->cdev = cdev;
> -	}
> -
>  	priv->cpu_dev = cpu_dev;
>  	priv->cpu_reg = cpu_reg;
>  	policy->driver_data = priv;
> @@ -287,7 +272,7 @@ static int cpufreq_init(struct cpufreq_policy
> *policy) if (ret) {
>  		dev_err(cpu_dev, "%s: invalid frequency table:
> %d\n", __func__, ret);
> -		goto out_cooling_unregister;
> +		goto free_table;
>  	}
>  
>  	policy->cpuinfo.transition_latency = transition_latency;
> @@ -300,8 +285,7 @@ static int cpufreq_init(struct cpufreq_policy
> *policy) 
>  	return 0;
>  
> -out_cooling_unregister:
> -	cpufreq_cooling_unregister(priv->cdev);
> +free_table:
>  	dev_pm_opp_free_cpufreq_table(cpu_dev, &freq_table);
>  out_free_priv:
>  	kfree(priv);
> @@ -342,11 +326,14 @@ static struct cpufreq_driver dt_cpufreq_driver
> = { 
>  static int dt_cpufreq_probe(struct platform_device *pdev)
>  {
> +	struct device_node *np;
>  	struct device *cpu_dev;
>  	struct regulator *cpu_reg;
>  	struct clk *cpu_clk;
>  	int ret;
>  
> +	/* at this point we checked the pointer already right? */
> +	np = of_node_get(pdev->dev.of_node);
>  	/*
>  	 * All per-cluster (CPUs sharing clock/voltages)
> initialization is done
>  	 * from ->init(). In probe(), we just need to make sure that
> clk and @@ -368,6 +355,28 @@ static int dt_cpufreq_probe(struct
> platform_device *pdev) if (ret)
>  		dev_err(cpu_dev, "failed register driver: %d\n",
> ret); 
> +	/*
> +	 * For now, just loading the cooling device;
> +	 * thermal DT code takes care of matching them.
> +	 */
> +	if (of_find_property(np, "#cooling-cells", NULL)) {
> +		struct cpufreq_policy policy;
> +		struct private_data *priv;
> +		struct thermal_cooling_device *cdev;
> +
> +		/* TODO: can cpu0 be always used ? */
> +		cpufreq_get_policy(&policy, 0);
> +		priv = policy.driver_data;
> +		cdev = of_cpufreq_cooling_register(np,
> cpu_present_mask);
> +		if (IS_ERR(cdev))
> +			dev_err(cpu_dev,
> +				"running cpufreq without cooling
> device: %ld\n",
> +				PTR_ERR(cdev));
> +		else
> +			priv->cdev = cdev;
> +	}
> +	of_node_put(np);
> +
>  	return ret;
>  }
>  
> diff --git a/drivers/thermal/cpu_cooling.c
> b/drivers/thermal/cpu_cooling.c index 1ab0018..342eb9e 100644
> --- a/drivers/thermal/cpu_cooling.c
> +++ b/drivers/thermal/cpu_cooling.c
> @@ -440,6 +440,11 @@ __cpufreq_cooling_register(struct device_node
> *np, int ret = 0, i;
>  	struct cpufreq_policy policy;
>  
> +	if (!cpufreq_get_current_driver()) {
> +		dev_warn(&pdev->dev, "no cpufreq driver,
> deferring.");
> +		return -EPROBE_DEFER;
> +	}
> +
>  	/* Verify that all the clip cpus have same freq_min,
> freq_max limit */ for_each_cpu(i, clip_cpus) {
>  		/* continue if cpufreq policy not found and not
> return error */ diff --git
> a/drivers/thermal/samsung/exynos_thermal_common.c
> b/drivers/thermal/samsung/exynos_thermal_common.c index
> 3f5ad25..f84975e 100644 ---
> a/drivers/thermal/samsung/exynos_thermal_common.c +++
> b/drivers/thermal/samsung/exynos_thermal_common.c @@ -373,7 +373,7 @@
> int exynos_register_thermal(struct thermal_sensor_conf *sensor_conf)
> if (IS_ERR(th_zone->cool_dev[th_zone->cool_dev_size]))
> { dev_err(sensor_conf->dev, "Failed to register cpufreq cooling
> device\n");
> -			ret = -EINVAL;
> +			ret =
> PTR_ERR(th_zone->cool_dev[th_zone->cool_dev_size]); goto
> err_unregister; }
>  		th_zone->cool_dev_size++;
> 
> 
> The above way, we avoid having same test in every driver that needs
> it. Besides, it makes sense the cpu_cooling code takes care of this
> check, as it is the very first part that has direct dependency with
> cpufreq.
> 
> > I only possess Exynos boards and Beagle Bone Black, so I'd be
> > grateful for testing proposed solution on other boards. The posted
> > code is compile tested.
> > 
> > This code applies on Eduardo's ti-soc-thermal-next tree:
> > SHA1: 208a97042d66d9bfbcfab0d4a00c9fe317bb73d3
> > 
> > Lukasz Majewski (8):
> >   thermal:cpu cooling:armada: Provide deferred probing for armada
> > driver thermal:cpu cooling:kirkwood: Provide deferred probing for
> > kirkwood driver
> >   thermal:cpu cooling:rcar: Provide deferred probing for rcar driver
> >   thermal:cpu cooling:spear: Provide deferred probing for spear
> > driver thermal:cpu cooling:tegra: Provide deferred probing for
> > tegra driver thermal:cpu cooling:ti: Provide deferred probing for
> > ti drivers thermal:core:fix: Initialize the max_state variable to 0
> >   thermal:core:fix: Check return code of the ->get_max_state()
> > callback
> > 
> >  drivers/thermal/armada_thermal.c            | 7 +++++++
> >  drivers/thermal/kirkwood_thermal.c          | 7 +++++++
> >  drivers/thermal/rcar_thermal.c              | 7 +++++++
> >  drivers/thermal/spear_thermal.c             | 7 +++++++
> >  drivers/thermal/tegra_soctherm.c            | 7 +++++++
> >  drivers/thermal/thermal_core.c              | 8 +++++---
> >  drivers/thermal/ti-soc-thermal/ti-bandgap.c | 7 +++++++
> >  7 files changed, 47 insertions(+), 3 deletions(-)
> > 
> > -- 
> > 2.0.0.rc2
> > 


-- 
Best regards,

Lukasz Majewski

Samsung R&D Institute Poland (SRPOL) | Linux Platform Group
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/