env: Implement lower priority arch_env_get_location()

Currently there is only one way to override desired environment location,
by implementing env_get_location(). This is increasingly being conflated
both on board level and architecture level, which leads to a problem on
boards where this function is already implemented on architecture level,
since those boards have no way to override this environment location on
board level anymore.

Implement arch_env_get_location() function which is architecture specific
and should only ever be implemented in architecture code. This function
has lower priority than env_get_location(), which should only ever be
implemented in board code, and which overrides the arch_env_get_location()
architecture environment selection.

This way, architecture can define its default environment chooser, while
board can now override it as needed at all times.

There is no functional change, since env_get_location() simply returns
arch_env_get_location(), and arch_env_get_location() implements the
current env_get_location() default content.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Adam Ford <aford173@gmail.com>
Cc: Fabio Estevam <festevam@denx.de>
Cc: Marek Behún <marek.behun@nic.cz>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Simon Glass <sjg@chromium.org>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Tim Harvey <tharvey@gateworks.com>
Cc: Tom Rini <trini@konsulko.com>
Cc: Tommaso Merciai <tomm.merciai@gmail.com>
Cc: Vladimir Oltean <vladimir.oltean@nxp.com>

env/env.c

@@ -109,6 +109,33 @@ static void env_set_inited(enum env_location location)
 	gd->env_has_init |= BIT(location);
 }
 
+/**
+ * arch_env_get_location() - Returns the best env location for an arch
+ * @op: operations performed on the environment
+ * @prio: priority between the multiple environments, 0 being the
+ *        highest priority
+ *
+ * This will return the preferred environment for the given priority.
+ * This is overridable by architectures if they need to and has lower
+ * priority than board side env_get_location() override.
+ *
+ * All implementations are free to use the operation, the priority and
+ * any other data relevant to their choice, but must take into account
+ * the fact that the lowest prority (0) is the most important location
+ * in the system. The following locations should be returned by order
+ * of descending priorities, from the highest to the lowest priority.
+ *
+ * Returns:
+ * an enum env_location value on success, a negative error code otherwise
+ */
+__weak enum env_location arch_env_get_location(enum env_operation op, int prio)
+{
+	if (prio >= ARRAY_SIZE(env_locations))
+		return ENVL_UNKNOWN;
+
+	return env_locations[prio];
+}
+
 /**
  * env_get_location() - Returns the best env location for a board
  * @op: operations performed on the environment
@@ -129,13 +156,9 @@ static void env_set_inited(enum env_location location)
  */
 __weak enum env_location env_get_location(enum env_operation op, int prio)
 {
-	if (prio >= ARRAY_SIZE(env_locations))
-		return ENVL_UNKNOWN;
-
-	return env_locations[prio];
+	return arch_env_get_location(op, prio);
 }
 
-
 /**
  * env_driver_lookup() - Finds the most suited environment location
  * @op: operations performed on the environment

include/env_internal.h

@@ -234,10 +234,26 @@ const char *env_ext4_get_intf(void);
  */
 const char *env_ext4_get_dev_part(void);
 
+/**
+ * arch_env_get_location()- Provide the best location for the U-Boot environment
+ *
+ * It is a weak function allowing board to overidde the environment location
+ * on architecture level. This has lower priority than env_get_location(),
+ * which can be defined on board level.
+ *
+ * @op: operations performed on the environment
+ * @prio: priority between the multiple environments, 0 being the
+ *        highest priority
+ * Return:  an enum env_location value on success, or -ve error code.
+ */
+enum env_location arch_env_get_location(enum env_operation op, int prio);
+
 /**
  * env_get_location()- Provide the best location for the U-Boot environment
  *
  * It is a weak function allowing board to overidde the environment location
+ * on board level. This has higher priority than arch_env_get_location(),
+ * which can be defined on architecture level.
  *
  * @op: operations performed on the environment
  * @prio: priority between the multiple environments, 0 being the