scsi: stex: Add S6 support

1. Add reboot notifier and register it in stex_probe for all supported
device.

2. For all supported device in restart flow, we get a callback from
notifier and set S6flag for stex_shutdown & stex_hba_stop to send
restart command to FW.

Signed-off-by: Charles.Chiou <[e-mail]>
Signed-off-by: Paul.Lyu <[e-mail]>
Signed-off-by: Martin K. Petersen <[e-mail]>

drivers/scsi/stex.c

···
 #include <linux/module.h>
 #include <linux/spinlock.h>
 #include <linux/ktime.h>
+#include <linux/reboot.h>
 #include <asm/io.h>
 #include <asm/irq.h>
 #include <asm/byteorder.h>
···
 	u16 rq_count;
 	u16 rq_size;
 	u16 sts_count;
+};
+
+int S6flag;
+static int stex_halt(struct notifier_block *nb, ulong event, void *buf);
+static struct notifier_block stex_notifier = {
+	stex_halt, NULL, 0
 };
 
 static int msi;
···
 
 	pci_set_master(pdev);
 
+	S6flag = 0;
+	register_reboot_notifier(&stex_notifier);
+
 	host = scsi_host_alloc(&driver_template, sizeof(struct st_hba));
 
 	if (!host) {
···
 	scsi_host_put(hba->host);
 
 	pci_disable_device(pdev);
+
+	unregister_reboot_notifier(&stex_notifier);
 }
 
 static void stex_shutdown(struct pci_dev *pdev)
 {
 	struct st_hba *hba = pci_get_drvdata(pdev);
 
-	if (hba->supports_pm == 0)
+	if (hba->supports_pm == 0) {
 		stex_hba_stop(hba, ST_IGNORED);
-	else
+	} else if (hba->supports_pm == 1 && S6flag) {
+		unregister_reboot_notifier(&stex_notifier);
+		stex_hba_stop(hba, ST_S6);
+	} else
 		stex_hba_stop(hba, ST_S5);
 }
 
···
 	hba->mu_status = MU_STATE_STARTING;
 	stex_handshake(hba);
 	return 0;
+}
+
+static int stex_halt(struct notifier_block *nb, unsigned long event, void *buf)
+{
+	S6flag = 1;
+	return NOTIFY_OK;
 }
 MODULE_DEVICE_TABLE(pci, stex_pci_tbl);