Re: [PATCH 0/8] thermal:cpu cooling:fix: Provide thermal core fixes with deferred probe for several drivers

Eduardo Valentin
2014-11-21T15:43:47Z

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Lukasz,

On Fri, Nov 21, 2014 at 09:33:48AM +0100, Lukasz Majewski wrote:
> 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/

I see. If I got correctly, with the above patch, we still need to have
the check for cpufreq driver in the thermal driver right?
quoting:
"In thermal driver probe the cpufreq_cooling_register() method presence
is crucial to evaluate if the thermal driver needs any actions with
-EPROBE_DEFER."

If yes, that means the proposal still leaves to drivers to deal with
the sequencing. For the patch above, I believe it is fine. However, a
better sequencing is still needed :-(.

For the case of of-thermal based drivers, it should be dealt between
cpu_cooling and cpufreq, as I proposed, bellow. I really agree that
drivers should not care about this, and thus we should not spread the
check among drivers, specially if there is nothing regarding cpufreq in
the driver's code. I might send the proposal of having the check between
cpu_cooling and cpufreq as a formal patch, in a separated thread.

I will have a look in your v2. Briefly looking, looks reasonable.

Once again, thanks.

Cheers,

Eduardo Valentin

>
>
> >
> > 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

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