[POWERPC] Setup RTAS values earlier, to enable rtas_call() earlier

Althought RTAS is instantiated when we enter the kernel, we can't actually
call into it until we know its entry point address. Currently we grab that
in rtas_initialize(), however that's quite late in the boot sequence.

To enable rtas_call() earlier, we can grab the RTAS entry etc. values while
we're scanning the flattened device tree. There's existing code to retrieve
the values from /chosen, however we don't store them there anymore, so remove
that code.
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kernel/prom.c

@@ -1125,24 +1125,6 @@ static int __init early_init_dt_scan_chosen(unsigned long node,
  		tce_alloc_end = *lprop;
 #endif
 
-#ifdef CONFIG_PPC_RTAS
-	/* To help early debugging via the front panel, we retrieve a minimal
-	 * set of RTAS infos now if available
-	 */
-	{
-		u64 *basep, *entryp, *sizep;
-
-		basep = of_get_flat_dt_prop(node, "linux,rtas-base", NULL);
-		entryp = of_get_flat_dt_prop(node, "linux,rtas-entry", NULL);
-		sizep = of_get_flat_dt_prop(node, "linux,rtas-size", NULL);
-		if (basep && entryp && sizep) {
-			rtas.base = *basep;
-			rtas.entry = *entryp;
-			rtas.size = *sizep;
-		}
-	}
-#endif /* CONFIG_PPC_RTAS */
-
 #ifdef CONFIG_KEXEC
        lprop = (u64*)of_get_flat_dt_prop(node, "linux,crashkernel-base", NULL);
        if (lprop)
@@ -1327,6 +1309,11 @@ void __init early_init_devtree(void *params)
 	/* Setup flat device-tree pointer */
 	initial_boot_params = params;
 
+#ifdef CONFIG_PPC_RTAS
+	/* Some machines might need RTAS info for debugging, grab it now. */
+	of_scan_flat_dt(early_init_dt_scan_rtas, NULL);
+#endif
+
 	/* Retrieve various informations from the /chosen node of the
 	 * device-tree, including the platform type, initrd location and
 	 * size, TCE reserve, and more ...

arch/powerpc/kernel/rtas.c

@@ -801,3 +801,25 @@ void __init rtas_initialize(void)
 	rtas_last_error_token = rtas_token("rtas-last-error");
 #endif
 }
+
+int __init early_init_dt_scan_rtas(unsigned long node,
+		const char *uname, int depth, void *data)
+{
+	u32 *basep, *entryp, *sizep;
+
+	if (depth != 1 || strcmp(uname, "rtas") != 0)
+		return 0;
+
+	basep  = of_get_flat_dt_prop(node, "linux,rtas-base", NULL);
+	entryp = of_get_flat_dt_prop(node, "linux,rtas-entry", NULL);
+	sizep  = of_get_flat_dt_prop(node, "rtas-size", NULL);
+
+	if (basep && entryp && sizep) {
+		rtas.base = *basep;
+		rtas.entry = *entryp;
+		rtas.size = *sizep;
+	}
+
+	/* break now */
+	return 1;
+}

include/asm-powerpc/rtas.h

@@ -181,6 +181,9 @@ extern int rtas_set_rtc_time(struct rtc_time *rtc_time);
 extern unsigned int rtas_busy_delay_time(int status);
 extern unsigned int rtas_busy_delay(int status);
 
+extern int early_init_dt_scan_rtas(unsigned long node,
+		const char *uname, int depth, void *data);
+
 extern void pSeries_log_error(char *buf, unsigned int err_type, int fatal);
 
 /* Error types logged.  */