dm: core: Add late driver remove option

Add another flag to the DM core which could be assigned to drivers and
which makes those drivers call their remove callbacks last, just before
booting OS and after all the other drivers finished with their remove
callbacks. This is necessary for things like clock drivers, where the
other drivers might depend on the clock driver in their remove callbacks.
Prime example is the mmc subsystem, which can reconfigure a card from HS
mode to slower modes in the remove callback and for that it needs to
reconfigure the controller clock.

Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
Signed-off-by: Simon Glass <sjg@chromium.org>

2 files changed, 33 insertions, 8 deletions

diff --git a/drivers/core/device-remove.c b/drivers/core/device-remove.c
index bc99ef0..616dcf0 100644
--- a/drivers/core/device-remove.c
+++ b/drivers/core/device-remove.c
@@ -47,20 +47,24 @@ int device_chld_remove(struct udevice *dev, struct driver *drv,
 		       uint flags)
 {
 	struct udevice *pos, *n;
-	int ret;
+	int result = 0;
 
 	assert(dev);
 
 	list_for_each_entry_safe(pos, n, &dev->child_head, sibling_node) {
+		int ret;
+
 		if (drv && (pos->driver != drv))
 			continue;
 
 		ret = device_remove(pos, flags);
-		if (ret && ret != -EKEYREJECTED)
+		if (ret == -EPROBE_DEFER)
+			result = ret;
+		else if (ret && ret != -EKEYREJECTED)
 			return ret;
 	}
 
-	return 0;
+	return result;
 }
 
 int device_unbind(struct udevice *dev)
@@ -154,21 +158,40 @@ void device_free(struct udevice *dev)
 /**
  * flags_remove() - Figure out whether to remove a device
  *
+ * If this is called with @flags == DM_REMOVE_NON_VITAL | DM_REMOVE_ACTIVE_DMA,
+ * then it returns 0 (=go head and remove) if the device is not matked vital
+ * but is marked DM_REMOVE_ACTIVE_DMA.
+ *
+ * If this is called with @flags == DM_REMOVE_ACTIVE_DMA,
+ * then it returns 0 (=go head and remove) if the device is marked
+ * DM_REMOVE_ACTIVE_DMA, regardless of whether it is marked vital.
+ *
  * @flags: Flags passed to device_remove()
  * @drv_flags: Driver flags
  * @return 0 if the device should be removed,
  * -EKEYREJECTED if @flags includes a flag in DM_REMOVE_ACTIVE_ALL but
  *	@drv_flags does not (indicates that this device has nothing to do for
  *	DMA shutdown or OS prepare)
+ * -EPROBE_DEFER if @flags is DM_REMOVE_NON_VITAL but @drv_flags contains
+ *	DM_FLAG_VITAL (indicates the device is vital and should not be removed)
  */
 static int flags_remove(uint flags, uint drv_flags)
 {
-	if (flags & DM_REMOVE_NORMAL)
-		return 0;
-	if (flags && (drv_flags & DM_REMOVE_ACTIVE_ALL))
-		return 0;
+	if (!(flags & DM_REMOVE_NORMAL)) {
+		bool vital_match;
+		bool active_match;
+
+		active_match = !(flags & DM_REMOVE_ACTIVE_ALL) ||
+			(drv_flags & flags);
+		vital_match = !(flags & DM_REMOVE_NON_VITAL) ||
+			!(drv_flags & DM_FLAG_VITAL);
+		if (!vital_match)
+			return -EPROBE_DEFER;
+		if (!active_match)
+			return -EKEYREJECTED;
+	}
 
-	return -EKEYREJECTED;
+	return 0;
 }
 
 int device_remove(struct udevice *dev, uint flags)
diff --git a/drivers/core/root.c b/drivers/core/root.c
index 2bfa75b..7ef2ec2 100644
--- a/drivers/core/root.c
+++ b/drivers/core/root.c
@@ -162,6 +162,8 @@ int dm_init(bool of_live)
 
 int dm_uninit(void)
 {
+	/* Remove non-vital devices first */
+	device_remove(dm_root(), DM_REMOVE_NON_VITAL);
 	device_remove(dm_root(), DM_REMOVE_NORMAL);
 	device_unbind(dm_root());
 	gd->dm_root = NULL;