hikey960: Fix race condition between hotplug and idles

From the hotplug testing on Hikey960, in some case cores fail to become
online in the system. When some cores are hotplugged off, if other
cores in the same cluster enter into CPU idle states at the meantime,
the cluster will be powered off. This introduces the state machine
malfunction in the power controller, thus when hotplug on the core
afterwards, it fails to boot up the core because the power controller
thinks the cluster is powered on.

This patch is to avoid race condition between hotplug and idles by
preventing cluster power off when some of cores in the cluster are
hotplugged off, if all cores in the same cluster are hotplugged off,
the cluster can be powered off.

Change-Id: Ib2feeb093357c70409a3536cb4f9da9b504fdcbe
Signed-off-by: Wei Yu <yuwei3@hisilicon.com>
Signed-off-by: Leo Yan <leo.yan@linaro.org>

plat/hisilicon/hikey960/drivers/pwrc/hisi_pwrc.c

@@ -147,13 +147,19 @@ void hisi_clear_cpuidle_flag(unsigned int cluster, unsigned int core)
 
 }
 
-int hisi_test_ap_suspend_flag(unsigned int cluster)
+int hisi_test_ap_suspend_flag(void)
 {
-	unsigned int val;
+	unsigned int val1;
+	unsigned int val2;
 
-	val = mmio_read_32(CPUIDLE_FLAG_REG(cluster));
-	val &= AP_SUSPEND_FLAG;
-	return !!val;
+	val1 = mmio_read_32(CPUIDLE_FLAG_REG(0));
+	val1 &= AP_SUSPEND_FLAG;
+
+	val2 = mmio_read_32(CPUIDLE_FLAG_REG(1));
+	val2 &= AP_SUSPEND_FLAG;
+
+	val1 |= val2;
+	return (val1 != 0);
 }
 
 void hisi_set_cluster_pwdn_flag(unsigned int cluster,
@@ -164,7 +170,8 @@ void hisi_set_cluster_pwdn_flag(unsigned int cluster,
 	hisi_cpuhotplug_lock(cluster, core);
 
 	val = mmio_read_32(REG_SCBAKDATA3_OFFSET);
-	val = (value << (cluster << 1)) | (val & 0xFFFFFFF);
+	val &= ~(0x3U << ((2 * cluster) + 28));
+	val |= (value << (2 * cluster));
 	mmio_write_32(REG_SCBAKDATA3_OFFSET, val);
 
 	hisi_cpuhotplug_unlock(cluster, core);
@@ -258,6 +265,17 @@ static unsigned int hisi_get_pdc_stat(unsigned int cluster)
 	return val;
 }
 
+static int check_hotplug(unsigned int cluster, unsigned int boot_flag)
+{
+	unsigned int mask = 0xF;
+
+	if (hisi_test_ap_suspend_flag() ||
+	    ((boot_flag & mask) == mask))
+		return 0;
+
+	return 1;
+}
+
 int hisi_test_pwrdn_allcores(unsigned int cluster, unsigned int core)
 {
 	unsigned int mask = 0xf << (core * 4);
@@ -268,7 +286,8 @@ int hisi_test_pwrdn_allcores(unsigned int cluster, unsigned int core)
 	mask = (PDC_COREPWRSTAT_MASK & (~mask));
 	pdc_stat &= mask;
 
-	if ((boot_flag ^ cpuidle_flag) || pdc_stat)
+	if ((boot_flag ^ cpuidle_flag) || pdc_stat ||
+	    check_hotplug(cluster, boot_flag))
 		return 0;
 	else
 		return 1;

plat/hisilicon/hikey960/drivers/pwrc/hisi_pwrc.h

@@ -39,7 +39,7 @@ void hisi_clear_cpu_boot_flag(unsigned int cluster, unsigned int core);
 int cluster_is_powered_on(unsigned int cluster);
 void hisi_enter_core_idle(unsigned int cluster, unsigned int core);
 void hisi_enter_cluster_idle(unsigned int cluster, unsigned int core);
-int hisi_test_ap_suspend_flag(unsigned int cluster);
+int hisi_test_ap_suspend_flag(void);
 void hisi_enter_ap_suspend(unsigned int cluster, unsigned int core);
 
 

plat/hisilicon/hikey960/hikey960_pm.c

@@ -228,7 +228,7 @@ static void hikey960_pwr_domain_suspend(const psci_power_state_t *target_state)
 			/* check the SR flag bit to determine
 			 * CLUSTER_IDLE_IPC or AP_SR_IPC to send
 			 */
-			if (hisi_test_ap_suspend_flag(cluster))
+			if (hisi_test_ap_suspend_flag())
 				hisi_enter_ap_suspend(cluster, core);
 			else
 				hisi_enter_cluster_idle(cluster, core);
@@ -268,7 +268,7 @@ hikey960_pwr_domain_suspend_finish(const psci_power_state_t *target_state)
 	hisi_clear_cpuidle_flag(cluster, core);
 	hisi_cpuidle_unlock(cluster, core);
 
-	if (hisi_test_ap_suspend_flag(cluster)) {
+	if (hisi_test_ap_suspend_flag()) {
 		hikey960_sr_dma_reinit();
 		gicv2_cpuif_enable();
 		console_pl011_register(uart_base, PL011_UART_CLK_IN_HZ,