ARM: mvebu: convert secondary CPU clock sync to hotplug state

The current call site in boot_secondary is causing sleep in invalid context
warnings, as this part of the code is running with interrrupts disabled and
some of the calls into the clock framework might sleep on a mutex.

Convert the secondary CPU clock sync to a hotplug state, which allows to
call it from a sleepable context.
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Gregory CLEMENT <gregory.clement@bootlin.com>

arch/arm/mach-mvebu/platsmp.c

@@ -35,6 +35,8 @@
 #define AXP_BOOTROM_BASE 0xfff00000
 #define AXP_BOOTROM_SIZE 0x100000
 
+static struct clk *boot_cpu_clk;
+
 static struct clk *get_cpu_clk(int cpu)
 {
 	struct clk *cpu_clk;
@@ -48,30 +50,6 @@ static struct clk *get_cpu_clk(int cpu)
 	return cpu_clk;
 }
 
-static void set_secondary_cpu_clock(unsigned int cpu)
-{
-	int thiscpu;
-	unsigned long rate;
-	struct clk *cpu_clk;
-
-	thiscpu = get_cpu();
-
-	cpu_clk = get_cpu_clk(thiscpu);
-	if (!cpu_clk)
-		goto out;
-	clk_prepare_enable(cpu_clk);
-	rate = clk_get_rate(cpu_clk);
-
-	cpu_clk = get_cpu_clk(cpu);
-	if (!cpu_clk)
-		goto out;
-	clk_set_rate(cpu_clk, rate);
-	clk_prepare_enable(cpu_clk);
-
-out:
-	put_cpu();
-}
-
 static int armada_xp_boot_secondary(unsigned int cpu, struct task_struct *idle)
 {
 	int ret, hw_cpu;
@@ -79,7 +57,6 @@ static int armada_xp_boot_secondary(unsigned int cpu, struct task_struct *idle)
 	pr_info("Booting CPU %d\n", cpu);
 
 	hw_cpu = cpu_logical_map(cpu);
-	set_secondary_cpu_clock(hw_cpu);
 	mvebu_pmsu_set_cpu_boot_addr(hw_cpu, armada_xp_secondary_startup);
 
 	/*
@@ -122,6 +99,19 @@ static void __init armada_xp_smp_init_cpus(void)
 		panic("Invalid number of CPUs in DT\n");
 }
 
+static int armada_xp_sync_secondary_clk(unsigned int cpu)
+{
+	struct clk *cpu_clk = get_cpu_clk(cpu);
+
+	if (!cpu_clk || !boot_cpu_clk)
+		return 0;
+
+	clk_prepare_enable(cpu_clk);
+	clk_set_rate(cpu_clk, clk_get_rate(boot_cpu_clk));
+
+	return 0;
+}
+
 static void __init armada_xp_smp_prepare_cpus(unsigned int max_cpus)
 {
 	struct device_node *node;
@@ -131,6 +121,14 @@ static void __init armada_xp_smp_prepare_cpus(unsigned int max_cpus)
 	flush_cache_all();
 	set_cpu_coherent();
 
+	boot_cpu_clk = get_cpu_clk(smp_processor_id());
+	if (boot_cpu_clk) {
+		clk_prepare_enable(boot_cpu_clk);
+		cpuhp_setup_state_nocalls(CPUHP_AP_ARM_MVEBU_SYNC_CLOCKS,
+					  "arm/mvebu/sync_clocks:online",
+					  armada_xp_sync_secondary_clk, NULL);
+	}
+
 	/*
 	 * In order to boot the secondary CPUs we need to ensure
 	 * the bootROM is mapped at the correct address.
@@ -223,7 +221,6 @@ static int mv98dx3236_boot_secondary(unsigned int cpu, struct task_struct *idle)
 	int ret, hw_cpu;
 
 	hw_cpu = cpu_logical_map(cpu);
-	set_secondary_cpu_clock(hw_cpu);
 	mv98dx3236_resume_set_cpu_boot_addr(hw_cpu,
 					    armada_xp_secondary_startup);
 

include/linux/cpuhotplug.h

@@ -143,6 +143,7 @@ enum cpuhp_state {
 	CPUHP_AP_SMPBOOT_THREADS,
 	CPUHP_AP_X86_VDSO_VMA_ONLINE,
 	CPUHP_AP_IRQ_AFFINITY_ONLINE,
+	CPUHP_AP_ARM_MVEBU_SYNC_CLOCKS,
 	CPUHP_AP_PERF_ONLINE,
 	CPUHP_AP_PERF_X86_ONLINE,
 	CPUHP_AP_PERF_X86_UNCORE_ONLINE,