[U-Boot] [PATCH v3] u-boot: remove driver lookup loop from env_save()

[Nicholas Faustini]

When called with ENVOP_SAVE, env_get_location() only returns the
gd->env_load_location variable without actually checking for
the environment location and priority.

This behaviour causes env_save() to fall into an infinite loop when
the low-level drv->save() call fails.

The env_save() function should not loop through the environment
location list but it should save the environment into the location
stored in gd->env_load_location by the last env_load() call.

Signed-off-by: Nicholas Faustini <nicholas.faustini at azcomtech.com>
---

Changes in v3:
- Add comment when env_load() fails and the env location is restored
- Introduce env_load_prio into gd struct. It stores the current
  priority of the environment location. Refactor of env_get_location()
  which acts the same on all the 'env_operation'

Changes in v2:
- Restore gd->env_load_location to the highest priority location when
  env_load() fails

 env/env.c                         | 35 +++++++++++++++++------------------
 include/asm-generic/global_data.h |  1 +
 2 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/env/env.c b/env/env.c
index 5c0842a..ba13ba8 100644
--- a/env/env.c
+++ b/env/env.c
@@ -119,21 +119,13 @@ static void env_set_inited(enum env_location location)
  */
 __weak enum env_location env_get_location(enum env_operation op, int prio)
 {
-	switch (op) {
-	case ENVOP_GET_CHAR:
-	case ENVOP_INIT:
-	case ENVOP_LOAD:
-		if (prio >= ARRAY_SIZE(env_locations))
-			return ENVL_UNKNOWN;
-
-		gd->env_load_location = env_locations[prio];
-		return gd->env_load_location;
-
-	case ENVOP_SAVE:
-		return gd->env_load_location;
-	}
+	if (prio >= ARRAY_SIZE(env_locations))
+		return ENVL_UNKNOWN;
+
+	gd->env_load_location = env_locations[prio];
+	gd->env_load_prio = prio;
 
-	return ENVL_UNKNOWN;
+	return gd->env_load_location;
 }
 
 
@@ -205,22 +197,29 @@ int env_load(void)
 			return 0;
 	}
 
+	/*
+	 * In case of invalid environment, we set the 'default' env location
+	 * to the highest priority. In this way, next calls to env_save()
+	 * will restore the environment at the right place.
+	 */
+	env_get_location(ENVOP_LOAD, 0);
+
 	return -ENODEV;
 }
 
 int env_save(void)
 {
 	struct env_driver *drv;
-	int prio;
 
-	for (prio = 0; (drv = env_driver_lookup(ENVOP_SAVE, prio)); prio++) {
+	drv = env_driver_lookup(ENVOP_SAVE, gd->env_load_prio);
+	if (drv) {
 		int ret;
 
 		if (!drv->save)
-			continue;
+			return -ENODEV;
 
 		if (!env_has_inited(drv->location))
-			continue;
+			return -ENODEV;
 
 		printf("Saving Environment to %s... ", drv->name);
 		ret = drv->save();
diff --git a/include/asm-generic/global_data.h b/include/asm-generic/global_data.h
index 2d451f8..319810a 100644
--- a/include/asm-generic/global_data.h
+++ b/include/asm-generic/global_data.h
@@ -51,6 +51,7 @@ typedef struct global_data {
 	unsigned long env_valid;	/* Environment valid? enum env_valid */
 	unsigned long env_has_init;	/* Bitmask of boolean of struct env_location offsets */
 	int env_load_location;
+	int env_load_prio;
 
 	unsigned long ram_top;		/* Top address of RAM used by U-Boot */
 	unsigned long relocaddr;	/* Start address of U-Boot in RAM */
-- 
2.7.4