mtd: phram: Repair multiple instances support

Commit b2a2a84d (mtd: phram: dot not crash when
built-in and passing boot param) claims to be "based on Ville Herva's similar
patch to block2mtd" (c4e7fb31), but it has
missed the crucial point of the original path: all these "if(n)def MODULE".
It has broken the possibility to create several phram instances when phram is
compiled as module. The possibility to add instances via /sys writes to
/sys/module/phram/parameters/phram was also broken with mentioned patch.
Proposed patch takes the idea of original block2mtd patch to its full extent.
Assumption "This function is always called before 'init_phram()'" was also
incorrect, so removed the comment. This patch effectively reverts also
b11ec57f (mtd: phram: fix section mismatch for
phram_setup).
Signed-off-by: Alexander Sverdlin <alexander.sverdlin@nsn.com>
[Brian: remove static assigment = 0]
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/devices/phram.c

@@ -205,6 +205,8 @@ static inline void kill_final_newline(char *str)
 	return 1;		\
 } while (0)
 
+#ifndef MODULE
+static int phram_init_called;
 /*
  * This shall contain the module parameter if any. It is of the form:
  * - phram=<device>,<address>,<size> for module case
@@ -213,9 +215,10 @@ static inline void kill_final_newline(char *str)
  * size.
  * Example: phram.phram=rootfs,0xa0000000,512Mi
  */
-static __initdata char phram_paramline[64 + 20 + 20];
+static char phram_paramline[64 + 20 + 20];
+#endif
 
-static int __init phram_setup(const char *val)
+static int phram_setup(const char *val)
 {
 	char buf[64 + 20 + 20], *str = buf;
 	char *token[3];
@@ -264,17 +267,36 @@ static int __init phram_setup(const char *val)
 	return ret;
 }
 
-static int __init phram_param_call(const char *val, struct kernel_param *kp)
+static int phram_param_call(const char *val, struct kernel_param *kp)
 {
+#ifdef MODULE
+	return phram_setup(val);
+#else
 	/*
-	 * This function is always called before 'init_phram()', whether
-	 * built-in or module.
+	 * If more parameters are later passed in via
+	 * /sys/module/phram/parameters/phram
+	 * and init_phram() has already been called,
+	 * we can parse the argument now.
 	 */
+
+	if (phram_init_called)
+		return phram_setup(val);
+
+	/*
+	 * During early boot stage, we only save the parameters
+	 * here. We must parse them later: if the param passed
+	 * from kernel boot command line, phram_param_call() is
+	 * called so early that it is not possible to resolve
+	 * the device (even kmalloc() fails). Defer that work to
+	 * phram_setup().
+	 */
+
 	if (strlen(val) >= sizeof(phram_paramline))
 		return -ENOSPC;
 	strcpy(phram_paramline, val);
 
 	return 0;
+#endif
 }
 
 module_param_call(phram, phram_param_call, NULL, NULL, 000);
@@ -283,10 +305,15 @@ MODULE_PARM_DESC(phram, "Memory region to map. \"phram=<name>,<start>,<length>\"
 
 static int __init init_phram(void)
 {
+	int ret = 0;
+
+#ifndef MODULE
 	if (phram_paramline[0])
-		return phram_setup(phram_paramline);
+		ret = phram_setup(phram_paramline);
+	phram_init_called = 1;
+#endif
 
-	return 0;
+	return ret;
 }
 
 static void __exit cleanup_phram(void)