cpufreq: Simplify core code related to boost support

Notice that the boost_supported field in struct cpufreq_driver is
redundant, because the driver's ->set_boost callback may be left
unset if "boost" is not supported. Moreover, the only driver
populating the ->set_boost callback is acpi_cpufreq, so make it
avoid populating that callback if "boost" is not supported, rework
the core to check ->set_boost instead of boost_supported to
verify "boost" support and drop boost_supported which isn't
used any more.

Signed-off-by: Rafael J. Wysocki <[e-mail]>
Acked-by: Viresh Kumar <[e-mail]>

drivers/cpufreq/acpi-cpufreq.c

···
 	int ret;
 	unsigned int val = 0;
 
-	if (!acpi_cpufreq_driver.boost_supported)
+	if (!acpi_cpufreq_driver.set_boost)
 		return -EINVAL;
 
 	ret = kstrtouint(buf, 10, &val);
···
 	.resume		= acpi_cpufreq_resume,
 	.name		= "acpi-cpufreq",
 	.attr		= acpi_cpufreq_attr,
-	.set_boost      = set_boost,
 };
 
 static void __init acpi_cpufreq_boost_init(void)
···
 		if (!msrs)
 			return;
 
-		acpi_cpufreq_driver.boost_supported = true;
+		acpi_cpufreq_driver.set_boost = set_boost;
 		acpi_cpufreq_driver.boost_enabled = boost_state(0);
 
 		cpu_notifier_register_begin();

drivers/cpufreq/cpufreq.c

···
 
 static bool cpufreq_boost_supported(void)
 {
-	return likely(cpufreq_driver) && cpufreq_driver->boost_supported;
+	return likely(cpufreq_driver) && cpufreq_driver->set_boost;
 }
 
 static int create_boost_sysfs_file(void)
 {
 	int ret;
-
-	if (!cpufreq_boost_supported())
-		return 0;
-
-	/*
-	 * Check if driver provides function to enable boost -
-	 * if not, use cpufreq_boost_set_sw as default
-	 */
-	if (!cpufreq_driver->set_boost)
-		cpufreq_driver->set_boost = cpufreq_boost_set_sw;
 
 	ret = sysfs_create_file(cpufreq_global_kobject, &boost.attr);
 	if (ret)
···
 	if (cpufreq_boost_supported())
 		return 0;
 
-	cpufreq_driver->boost_supported = true;
+	cpufreq_driver->set_boost = cpufreq_boost_set_sw;
 
 	/* This will get removed on driver unregister */
 	return create_boost_sysfs_file();
···
 	if (driver_data->setpolicy)
 		driver_data->flags |= CPUFREQ_CONST_LOOPS;
 
-	ret = create_boost_sysfs_file();
-	if (ret)
-		goto err_null_driver;
+	if (cpufreq_boost_supported()) {
+		ret = create_boost_sysfs_file();
+		if (ret)
+			goto err_null_driver;
+	}
 
 	ret = subsys_interface_register(&cpufreq_interface);
 	if (ret)

include/linux/cpufreq.h

···
 	struct freq_attr **attr;
 
 	/* platform specific boost support code */
-	bool		boost_supported;
 	bool		boost_enabled;
 	int		(*set_boost)(int state);
 };