powerpc/powernv: Make possible for user to force a full ipl cec reboot

Ever since fast reboot is enabled by default in opal,
opal_cec_reboot() will use fast-reset instead of full IPL to perform
system reboot. This leaves the user with no direct way to force a full
IPL reboot except changing an nvram setting that persistently disables
fast-reset for all subsequent reboots.

This patch provides a more direct way for the user to force a one-shot
full IPL reboot by passing the command line argument 'full' to the
reboot command. So the user will be able to tweak the reboot behavior
via:

  $ sudo reboot full	# Force a full ipl reboot skipping fast-reset

  or
  $ sudo reboot  	# default reboot path (usually fast-reset)

The reboot command passes the un-parsed command argument to the kernel
via the 'Reboot' syscall which is then passed on to the arch function
pnv_restart(). The patch updates pnv_restart() to handle this cmd-arg
and issues opal_cec_reboot2 with OPAL_REBOOT_FULL_IPL to force a full
IPL reset.
Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
Acked-by: Andrew Donnellan <andrew.donnellan@au1.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/opal-api.h

@@ -1050,6 +1050,7 @@ enum OpalSysCooling {
 enum {
 	OPAL_REBOOT_NORMAL		= 0,
 	OPAL_REBOOT_PLATFORM_ERROR	= 1,
+	OPAL_REBOOT_FULL_IPL		= 2,
 };
 
 /* Argument to OPAL_PCI_TCE_KILL */

arch/powerpc/platforms/powernv/setup.c

@@ -219,17 +219,41 @@ static void pnv_prepare_going_down(void)
 
 static void  __noreturn pnv_restart(char *cmd)
 {
-	long rc = OPAL_BUSY;
+	long rc;
 
 	pnv_prepare_going_down();
 
-	while (rc == OPAL_BUSY || rc == OPAL_BUSY_EVENT) {
-		rc = opal_cec_reboot();
-		if (rc == OPAL_BUSY_EVENT)
-			opal_poll_events(NULL);
+	do {
+		if (!cmd)
+			rc = opal_cec_reboot();
+		else if (strcmp(cmd, "full") == 0)
+			rc = opal_cec_reboot2(OPAL_REBOOT_FULL_IPL, NULL);
 		else
+			rc = OPAL_UNSUPPORTED;
+
+		if (rc == OPAL_BUSY || rc == OPAL_BUSY_EVENT) {
+			/* Opal is busy wait for some time and retry */
+			opal_poll_events(NULL);
 			mdelay(10);
-	}
+
+		} else	if (cmd && rc) {
+			/* Unknown error while issuing reboot */
+			if (rc == OPAL_UNSUPPORTED)
+				pr_err("Unsupported '%s' reboot.\n", cmd);
+			else
+				pr_err("Unable to issue '%s' reboot. Err=%ld\n",
+				       cmd, rc);
+			pr_info("Forcing a cec-reboot\n");
+			cmd = NULL;
+			rc = OPAL_BUSY;
+
+		} else if (rc != OPAL_SUCCESS) {
+			/* Unknown error while issuing cec-reboot */
+			pr_err("Unable to reboot. Err=%ld\n", rc);
+		}
+
+	} while (rc == OPAL_BUSY || rc == OPAL_BUSY_EVENT);
+
 	for (;;)
 		opal_poll_events(NULL);
 }