thermal: ti-soc-thermal: Enable addition power management

The bandgap sensor can be idled when the processor is too, but it
isn't currently being done, so the power consumption of OMAP3
boards can elevated if the bangap sensor is enabled.

This patch attempts to use some additional power management
to idle the clock to the bandgap when not needed.
Signed-off-by: Adam Ford <aford173@gmail.com>
Reported-by: kernel test robot <lkp@intel.com>
Tested-by: Andreas Kemnade <andreas@kemnade.info> # GTA04
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20200911123157.759379-1-aford173@gmail.com

drivers/thermal/ti-soc-thermal/ti-bandgap.c

@@ -25,10 +25,20 @@
 #include <linux/of_platform.h>
 #include <linux/of_irq.h>
 #include <linux/io.h>
+#include <linux/cpu_pm.h>
+#include <linux/device.h>
+#include <linux/pm_runtime.h>
+#include <linux/pm.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
 
 #include "ti-bandgap.h"
 
 static int ti_bandgap_force_single_read(struct ti_bandgap *bgp, int id);
+#ifdef CONFIG_PM_SLEEP
+static int bandgap_omap_cpu_notifier(struct notifier_block *nb,
+				  unsigned long cmd, void *v);
+#endif
 
 /***   Helper functions to access registers and their bitfields   ***/
 
@@ -1008,6 +1018,11 @@ int ti_bandgap_probe(struct platform_device *pdev)
 		}
 	}
 
+#ifdef CONFIG_PM_SLEEP
+	bgp->nb.notifier_call = bandgap_omap_cpu_notifier;
+	cpu_pm_register_notifier(&bgp->nb);
+#endif
+
 	return 0;
 
 remove_last_cooling:
@@ -1041,7 +1056,9 @@ int ti_bandgap_remove(struct platform_device *pdev)
 	struct ti_bandgap *bgp = platform_get_drvdata(pdev);
 	int i;
 
-	/* First thing is to remove sensor interfaces */
+	cpu_pm_unregister_notifier(&bgp->nb);
+
+	/* Remove sensor interfaces */
 	for (i = 0; i < bgp->conf->sensor_count; i++) {
 		if (bgp->conf->sensors[i].unregister_cooling)
 			bgp->conf->sensors[i].unregister_cooling(bgp, i);
@@ -1150,9 +1167,43 @@ static int ti_bandgap_suspend(struct device *dev)
 	if (TI_BANDGAP_HAS(bgp, CLK_CTRL))
 		clk_disable_unprepare(bgp->fclock);
 
+	bgp->is_suspended = true;
+
 	return err;
 }
 
+static int bandgap_omap_cpu_notifier(struct notifier_block *nb,
+				  unsigned long cmd, void *v)
+{
+	struct ti_bandgap *bgp;
+
+	bgp = container_of(nb, struct ti_bandgap, nb);
+
+	spin_lock(&bgp->lock);
+	switch (cmd) {
+	case CPU_CLUSTER_PM_ENTER:
+		if (bgp->is_suspended)
+			break;
+		ti_bandgap_save_ctxt(bgp);
+		ti_bandgap_power(bgp, false);
+		if (TI_BANDGAP_HAS(bgp, CLK_CTRL))
+			clk_disable(bgp->fclock);
+		break;
+	case CPU_CLUSTER_PM_ENTER_FAILED:
+	case CPU_CLUSTER_PM_EXIT:
+		if (bgp->is_suspended)
+			break;
+		if (TI_BANDGAP_HAS(bgp, CLK_CTRL))
+			clk_enable(bgp->fclock);
+		ti_bandgap_power(bgp, true);
+		ti_bandgap_restore_ctxt(bgp);
+		break;
+	}
+	spin_unlock(&bgp->lock);
+
+	return NOTIFY_OK;
+}
+
 static int ti_bandgap_resume(struct device *dev)
 {
 	struct ti_bandgap *bgp = dev_get_drvdata(dev);
@@ -1161,6 +1212,7 @@ static int ti_bandgap_resume(struct device *dev)
 		clk_prepare_enable(bgp->fclock);
 
 	ti_bandgap_power(bgp, true);
+	bgp->is_suspended = false;
 
 	return ti_bandgap_restore_ctxt(bgp);
 }

drivers/thermal/ti-soc-thermal/ti-bandgap.h

@@ -12,6 +12,10 @@
 #include <linux/spinlock.h>
 #include <linux/types.h>
 #include <linux/err.h>
+#include <linux/cpu_pm.h>
+#include <linux/device.h>
+#include <linux/pm_runtime.h>
+#include <linux/pm.h>
 
 struct gpio_desc;
 
@@ -203,6 +207,8 @@ struct ti_bandgap {
 	int				irq;
 	struct gpio_desc		*tshut_gpiod;
 	u32				clk_rate;
+	struct notifier_block		nb;
+	unsigned int is_suspended:1;
 };
 
 /**