[PATCH v3 08/22] PM / devfreq: tegra30: Move clk-notifier's registration to governor's start

[Dmitry Osipenko]

There is no point in receiving of the notifications while governor is
stopped, let's keep them disabled like we do for the CPU freq-change
notifications. This also fixes a potential use-after-free bug if
notification happens after device's removal.

Signed-off-by: Dmitry Osipenko <dig...@gmail.com>
---
 drivers/devfreq/tegra30-devfreq.c | 33 ++++++++++++++++++-------------
 1 file changed, 19 insertions(+), 14 deletions(-)

diff --git a/drivers/devfreq/tegra30-devfreq.c 
b/drivers/devfreq/tegra30-devfreq.c
index 502511ac4602..1751d17f9a1c 100644
--- a/drivers/devfreq/tegra30-devfreq.c
+++ b/drivers/devfreq/tegra30-devfreq.c
@@ -575,6 +575,19 @@ static int tegra_actmon_start(struct tegra_devfreq *tegra)
        actmon_writel(tegra, ACTMON_SAMPLING_PERIOD - 1,
                      ACTMON_GLB_PERIOD_CTRL);
 
+       /*
+        * CLK notifications are needed in order to reconfigure the upper
+        * consecutive watermark in accordance to the actual clock rate
+        * to avoid unnecessary upper interrupts.
+        */
+       err = clk_notifier_register(tegra->emc_clock,
+                                   &tegra->clk_rate_change_nb);
+       if (err) {
+               dev_err(tegra->devfreq->dev.parent,
+                       "Failed to register rate change notifier\n");
+               return err;
+       }
+
        for (i = 0; i < ARRAY_SIZE(tegra->devices); i++)
                tegra_actmon_configure_device(tegra, &tegra->devices[i]);
 
@@ -601,6 +614,8 @@ static int tegra_actmon_start(struct tegra_devfreq *tegra)
        for (i = 0; i < ARRAY_SIZE(tegra->devices); i++)
                tegra_actmon_stop_device(&tegra->devices[i]);
 
+       clk_notifier_unregister(tegra->emc_clock, &tegra->clk_rate_change_nb);
+
        return err;
 }
 
@@ -617,6 +632,8 @@ static void tegra_actmon_stop(struct tegra_devfreq *tegra)
 
        for (i = 0; i < ARRAY_SIZE(tegra->devices); i++)
                tegra_actmon_stop_device(&tegra->devices[i]);
+
+       clk_notifier_unregister(tegra->emc_clock, &tegra->clk_rate_change_nb);
 }
 
 static int tegra_devfreq_target(struct device *dev, unsigned long *freq,
@@ -861,22 +878,14 @@ static int tegra_devfreq_probe(struct platform_device 
*pdev)
 
        platform_set_drvdata(pdev, tegra);
 
+       tegra->clk_rate_change_nb.notifier_call = tegra_actmon_clk_notify_cb;
        tegra->cpu_rate_change_nb.notifier_call = tegra_actmon_cpu_notify_cb;
        INIT_WORK(&tegra->update_work, tegra_actmon_delayed_update);
 
-       tegra->clk_rate_change_nb.notifier_call = tegra_actmon_clk_notify_cb;
-       err = clk_notifier_register(tegra->emc_clock,
-                                   &tegra->clk_rate_change_nb);
-       if (err) {
-               dev_err(&pdev->dev,
-                       "Failed to register rate change notifier\n");
-               goto remove_opps;
-       }
-
        err = devfreq_add_governor(&tegra_devfreq_governor);
        if (err) {
                dev_err(&pdev->dev, "Failed to add governor: %d\n", err);
-               goto unreg_notifier;
+               goto remove_opps;
        }
 
        tegra_devfreq_profile.initial_freq = clk_get_rate(tegra->emc_clock);
@@ -892,9 +901,6 @@ static int tegra_devfreq_probe(struct platform_device *pdev)
 remove_governor:
        devfreq_remove_governor(&tegra_devfreq_governor);
 
-unreg_notifier:
-       clk_notifier_unregister(tegra->emc_clock, &tegra->clk_rate_change_nb);
-
 remove_opps:
        dev_pm_opp_remove_all_dynamic(&pdev->dev);
 
@@ -911,7 +917,6 @@ static int tegra_devfreq_remove(struct platform_device 
*pdev)
        devfreq_remove_device(tegra->devfreq);
        devfreq_remove_governor(&tegra_devfreq_governor);
 
-       clk_notifier_unregister(tegra->emc_clock, &tegra->clk_rate_change_nb);
        dev_pm_opp_remove_all_dynamic(&pdev->dev);
 
        reset_control_reset(tegra->reset);
-- 
2.22.0