ARM: zynq: Synchronise zynq_cpu_die/kill

Avoid races and add synchronisation between the arch specific
kill and die routines.

The same synchronisation issue was fixed on IMX platform
by this commit:
"ARM: imx: fix sync issue between imx_cpu_die and imx_cpu_kill"
(sha1: 2f3edfd7)
Signed-off-by: Soren Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>

arch/arm/mach-zynq/common.h

@@ -24,6 +24,8 @@ extern int zynq_early_slcr_init(void);
 extern void zynq_slcr_system_reset(void);
 extern void zynq_slcr_cpu_stop(int cpu);
 extern void zynq_slcr_cpu_start(int cpu);
+extern bool zynq_slcr_cpu_state_read(int cpu);
+extern void zynq_slcr_cpu_state_write(int cpu, bool die);
 extern u32 zynq_slcr_get_device_id(void);
 
 #ifdef CONFIG_SMP

arch/arm/mach-zynq/hotplug.c

@@ -19,6 +19,8 @@
  */
 void zynq_platform_cpu_die(unsigned int cpu)
 {
+	zynq_slcr_cpu_state_write(cpu, true);
+
 	/*
 	 * there is no power-control hardware on this platform, so all
 	 * we can do is put the core into WFI; this is safe as the calling

arch/arm/mach-zynq/platsmp.c

@@ -127,6 +127,12 @@ static void zynq_secondary_init(unsigned int cpu)
 #ifdef CONFIG_HOTPLUG_CPU
 static int zynq_cpu_kill(unsigned cpu)
 {
+	unsigned long timeout = jiffies + msecs_to_jiffies(50);
+
+	while (zynq_slcr_cpu_state_read(cpu))
+		if (time_after(jiffies, timeout))
+			return 0;
+
 	zynq_slcr_cpu_stop(cpu);
 	return 1;
 }

arch/arm/mach-zynq/slcr.c

@@ -138,6 +138,8 @@ void zynq_slcr_cpu_start(int cpu)
 	zynq_slcr_write(reg, SLCR_A9_CPU_RST_CTRL_OFFSET);
 	reg &= ~(SLCR_A9_CPU_CLKSTOP << cpu);
 	zynq_slcr_write(reg, SLCR_A9_CPU_RST_CTRL_OFFSET);
+
+	zynq_slcr_cpu_state_write(cpu, false);
 }
 
 /**
@@ -154,8 +156,47 @@ void zynq_slcr_cpu_stop(int cpu)
 }
 
 /**
- * zynq_slcr_init - Regular slcr driver init
+ * zynq_slcr_cpu_state - Read/write cpu state
+ * @cpu:	cpu number
  *
+ * SLCR_REBOOT_STATUS save upper 2 bits (31/30 cpu states for cpu0 and cpu1)
+ * 0 means cpu is running, 1 cpu is going to die.
+ *
+ * Return: true if cpu is running, false if cpu is going to die
+ */
+bool zynq_slcr_cpu_state_read(int cpu)
+{
+	u32 state;
+
+	state = readl(zynq_slcr_base + SLCR_REBOOT_STATUS_OFFSET);
+	state &= 1 << (31 - cpu);
+
+	return !state;
+}
+
+/**
+ * zynq_slcr_cpu_state - Read/write cpu state
+ * @cpu:	cpu number
+ * @die:	cpu state - true if cpu is going to die
+ *
+ * SLCR_REBOOT_STATUS save upper 2 bits (31/30 cpu states for cpu0 and cpu1)
+ * 0 means cpu is running, 1 cpu is going to die.
+ */
+void zynq_slcr_cpu_state_write(int cpu, bool die)
+{
+	u32 state, mask;
+
+	state = readl(zynq_slcr_base + SLCR_REBOOT_STATUS_OFFSET);
+	mask = 1 << (31 - cpu);
+	if (die)
+		state |= mask;
+	else
+		state &= ~mask;
+	writel(state, zynq_slcr_base + SLCR_REBOOT_STATUS_OFFSET);
+}
+
+/**
+ * zynq_slcr_init - Regular slcr driver init
  * Return:	0 on success, negative errno otherwise.
  *
  * Called early during boot from platform code to remap SLCR area.