thermal: ti-soc-thermal: Disable the CPU PM notifier for OMAP4430

It has been observed that on OMAP4430 (ES2.0, ES2.1 and ES2.3) the enabled
notifier causes errors on the DTEMP readout values:

ti-soc-thermal 4a002260.bandgap: in range ADC val: 52
ti-soc-thermal 4a002260.bandgap: in range ADC val: 64
ti-soc-thermal 4a002260.bandgap: in range ADC val: 64
ti-soc-thermal 4a002260.bandgap: out of range ADC val: 0
thermal thermal_zone0: failed to read out thermal zone (-5)
ti-soc-thermal 4a002260.bandgap: out of range ADC val: 0
thermal thermal_zone0: failed to read out thermal zone (-5)
ti-soc-thermal 4a002260.bandgap: out of range ADC val: 4
thermal thermal_zone0: failed to read out thermal zone (-5)
ti-soc-thermal 4a002260.bandgap: in range ADC val: 100

raw 100 translates to 133 Celsius on omap4-sdp, triggering shutdown due to
critical temperature.

When the notifier is disable for OMAP4430 the DTEMP values are stable:
ti-soc-thermal 4a002260.bandgap: in range ADC val: 56
ti-soc-thermal 4a002260.bandgap: in range ADC val: 56
ti-soc-thermal 4a002260.bandgap: in range ADC val: 57
ti-soc-thermal 4a002260.bandgap: in range ADC val: 57
ti-soc-thermal 4a002260.bandgap: in range ADC val: 56

Fixes: 5093402 ("thermal: ti-soc-thermal: Enable addition power management")
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
Tested-by: Tony Lindgren <tony@atomide.com>
Acked-by: Keerthy <j-keerthy@ti.com>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/20201029100335.27665-1-peter.ujfalusi@ti.com

Author: Peter Ujfalusi

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

@@ -20,6 +20,7 @@
 #include <linux/err.h>
 #include <linux/types.h>
 #include <linux/spinlock.h>
+#include <linux/sys_soc.h>
 #include <linux/reboot.h>
 #include <linux/of_device.h>
 #include <linux/of_platform.h>
@@ -864,6 +865,17 @@ static struct ti_bandgap *ti_bandgap_build(struct platform_device *pdev)
 	return bgp;
 }
 
+/*
+ * List of SoCs on which the CPU PM notifier can cause erros on the DTEMP
+ * readout.
+ * Enabled notifier on these machines results in erroneous, random values which
+ * could trigger unexpected thermal shutdown.
+ */
+static const struct soc_device_attribute soc_no_cpu_notifier[] = {
+	{ .machine = "OMAP4430" },
+	{ /* sentinel */ },
+};
+
 /***   Device driver call backs   ***/
 
 static
@@ -1020,7 +1032,8 @@ 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);
+	if (!soc_device_match(soc_no_cpu_notifier))
+		cpu_pm_register_notifier(&bgp->nb);
 #endif
 
 	return 0;
@@ -1056,7 +1069,8 @@ int ti_bandgap_remove(struct platform_device *pdev)
 	struct ti_bandgap *bgp = platform_get_drvdata(pdev);
 	int i;
 
-	cpu_pm_unregister_notifier(&bgp->nb);
+	if (!soc_device_match(soc_no_cpu_notifier))
+		cpu_pm_unregister_notifier(&bgp->nb);
 
 	/* Remove sensor interfaces */
 	for (i = 0; i < bgp->conf->sensor_count; i++) {