stm32mp1: psci: add synchronization with ROM code

Use SGI0 interruption  and TAMP_BACKUP_MAGIC_NUMBER
to synchronize the core1 boot sequence requested by
core0 in psci_cpu_on():
- a initial interruption is needed in ROM code after
  RCC_MP_GRSTCSETR_MPUP1RST (psci_cpu_off)
- the ROM code set to 0 the 2 registers
  + TAMP_BACKUP_BRANCH_ADDRESS
  + TAMP_BACKUP_MAGIC_NUMBER
  when magic is not egual to
  BOOT_API_A7_CORE0_MAGIC_NUMBER

This patch solve issue for cpu1 restart in kernel.
echo 0 > /sys/devices/system/cpu/cpu1/online
echo 1 > /sys/devices/system/cpu/cpu1/online
Signed-off-by: NPatrick Delaunay <patrick.delaunay@st.com>

arch/arm/mach-stm32mp/psci.c

@@ -47,14 +47,14 @@ static u32 __secure stm32mp_get_gicd_base_address(void)
 	return (periphbase & CBAR_MASK) + GIC_DIST_OFFSET;
 }
 
-static void __secure stm32mp_smp_kick_all_cpus(void)
+static void __secure stm32mp_raise_sgi0(int cpu)
 {
 	u32 gic_dist_addr;
 
 	gic_dist_addr = stm32mp_get_gicd_base_address();
 
-	/* kick all CPUs (except this one) by writing to GICD_SGIR */
-	writel(1U << 24, gic_dist_addr + GICD_SGIR);
+	/* ask cpu with SGI0 */
+	writel((BIT(cpu) << 16), gic_dist_addr + GICD_SGIR);
 }
 
 void __secure psci_arch_cpu_entry(void)
@@ -62,6 +62,9 @@ void __secure psci_arch_cpu_entry(void)
 	u32 cpu = psci_get_cpu_id();
 
 	psci_set_state(cpu, PSCI_AFFINITY_LEVEL_ON);
+
+	/* reset magic in TAMP register */
+	writel(0xFFFFFFFF, TAMP_BACKUP_MAGIC_NUMBER);
 }
 
 int __secure psci_features(u32 function_id, u32 psci_fid)
@@ -127,6 +130,16 @@ int __secure psci_cpu_on(u32 function_id, u32 target_cpu, u32 pc,
 	if (psci_state[cpu] == PSCI_AFFINITY_LEVEL_ON)
 		return ARM_PSCI_RET_ALREADY_ON;
 
+	/* reset magic in TAMP register */
+	if (readl(TAMP_BACKUP_MAGIC_NUMBER))
+		writel(0xFFFFFFFF, TAMP_BACKUP_MAGIC_NUMBER);
+	/*
+	 * ROM code need a first SGI0 after core reset
+	 * core is ready when magic is set to 0 in ROM code
+	 */
+	while (readl(TAMP_BACKUP_MAGIC_NUMBER))
+		stm32mp_raise_sgi0(cpu);
+
 	/* store target PC and context id*/
 	psci_save(cpu, pc, context_id);
 
@@ -142,7 +155,8 @@ int __secure psci_cpu_on(u32 function_id, u32 target_cpu, u32 pc,
 		writel(BOOT_API_A7_CORE0_MAGIC_NUMBER,
 		       TAMP_BACKUP_MAGIC_NUMBER);
 
-	stm32mp_smp_kick_all_cpus();
+	/* Generate an IT to start the core */
+	stm32mp_raise_sgi0(cpu);
 
 	return ARM_PSCI_RET_SUCCESS;
 }