cpufreq: rockchip: handle -EPROBE_DEFER for late PMIC initialization

On boards like Youyeetoo YY3588 where the RK806 PMIC initializes late,
the cpufreq driver would fail to get the CPU regulator and abort probe.
This caused CPU frequency scaling to be unavailable.

Handle -EPROBE_DEFER from regulator_get_optional() to allow the driver
to retry when the PMIC becomes available.

Author: SuperKali

drivers/cpufreq/rockchip-cpufreq.c

@@ -17,6 +17,7 @@
 #include <linux/cpu.h>
 #include <linux/cpufreq.h>
 #include <linux/cpuidle.h>
+#include <linux/delay.h>
 #include <linux/err.h>
 #include <linux/init.h>
 #include <linux/kernel.h>
@@ -33,6 +34,7 @@
 #include <linux/regmap.h>
 #include <linux/regulator/consumer.h>
 #include <linux/rockchip/cpu.h>
+#include <linux/workqueue.h>
 #include <soc/rockchip/rockchip_opp_select.h>
 #include <soc/rockchip/rockchip_system_monitor.h>
 
@@ -54,6 +56,11 @@ struct cluster_info {
 };
 static LIST_HEAD(cluster_info_list);
 
+#define CPUFREQ_DEFER_DELAY_MS	100
+#define CPUFREQ_DEFER_RETRIES	50
+static struct delayed_work cpufreq_defer_work;
+static int cpufreq_defer_retry_count;
+
 static struct cluster_info *rockchip_cluster_info_lookup(int cpu);
 
 static int px30_get_soc_info(struct device *dev, struct device_node *np,
@@ -861,7 +868,7 @@ static struct notifier_block rockchip_cpufreq_panic_notifier_block = {
 	.notifier_call = rockchip_cpufreq_panic_notifier,
 };
 
-static int __init rockchip_cpufreq_driver_init(void)
+static int rockchip_cpufreq_do_init(void)
 {
 	struct cluster_info *cluster, *pos;
 	struct cpufreq_dt_platform_data pdata = {0};
@@ -881,6 +888,9 @@ static int __init rockchip_cpufreq_driver_init(void)
 
 		ret = rockchip_cpufreq_cluster_init(cpu, cluster);
 		if (ret) {
+			kfree(cluster);
+			if (ret == -EPROBE_DEFER)
+				goto release_cluster_info;
 			pr_err("Failed to initialize dvfs info cpu%d\n", cpu);
 			goto release_cluster_info;
 		}
@@ -929,7 +939,44 @@ static int __init rockchip_cpufreq_driver_init(void)
 	}
 	return ret;
 }
-module_init(rockchip_cpufreq_driver_init);
+
+static void rockchip_cpufreq_defer_work_func(struct work_struct *work)
+{
+	int ret;
+
+	ret = rockchip_cpufreq_do_init();
+	if (ret == -EPROBE_DEFER) {
+		if (++cpufreq_defer_retry_count < CPUFREQ_DEFER_RETRIES) {
+			pr_debug("cpufreq: regulator not ready, retry %d/%d\n",
+				 cpufreq_defer_retry_count, CPUFREQ_DEFER_RETRIES);
+			schedule_delayed_work(&cpufreq_defer_work,
+					      msecs_to_jiffies(CPUFREQ_DEFER_DELAY_MS));
+		} else {
+			pr_err("cpufreq: gave up waiting for regulator after %d retries\n",
+			       CPUFREQ_DEFER_RETRIES);
+		}
+	} else if (ret) {
+		pr_err("cpufreq: initialization failed with error %d\n", ret);
+	}
+}
+
+static int __init rockchip_cpufreq_driver_init(void)
+{
+	int ret;
+
+	ret = rockchip_cpufreq_do_init();
+	if (ret == -EPROBE_DEFER) {
+		pr_info("cpufreq: regulator not ready, deferring initialization\n");
+		INIT_DELAYED_WORK(&cpufreq_defer_work,
+				  rockchip_cpufreq_defer_work_func);
+		schedule_delayed_work(&cpufreq_defer_work,
+				      msecs_to_jiffies(CPUFREQ_DEFER_DELAY_MS));
+		return 0;
+	}
+
+	return ret;
+}
+late_initcall(rockchip_cpufreq_driver_init);
 
 MODULE_AUTHOR("Finley Xiao <finley.xiao@rock-chips.com>");
 MODULE_DESCRIPTION("Rockchip cpufreq driver");