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

From: Eduardo Valentin
Date: Thu Nov 20 2014 - 13:54:34 EST

Lukasz,

Thanks for the keeping this up. And apologize for late answer.

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
>

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