dm: Allow drivers to be marked 'before relocation'

Driver model currently only operates after relocation is complete. In this
state U-Boot typically has a small amount of memory available. In adding
support for driver model prior to relocation we must try to use as little
memory as possible.

In addition, on some machines the memory has not be inited and/or the CPU
is not running at full speed or the data cache is off. These can reduce
execution performance, so the less initialisation that is done before
relocation the better.

An immediately-obvious improvement is to only initialise drivers which are
actually going to be used before relocation. On many boards the only such
driver is a serial UART, so this provides a very large potential benefit.

Allow drivers to mark themselves as 'pre-reloc' which means that they will
be initialised prior to relocation. This can be done either with a driver
flag or with a 'dm,pre-reloc' device tree property.

To support this, the various dm scanning function now take a 'pre_reloc_only'
parameter which indicates that only drivers marked pre-reloc should be
bound.

Signed-off-by: Simon Glass <sjg@chromium.org>

4 files changed, 16 insertions, 5 deletions

diff --git a/include/dm/device-internal.h b/include/dm/device-internal.h
index 26e5cf5..7005d03 100644
--- a/include/dm/device-internal.h
+++ b/include/dm/device-internal.h
@@ -45,12 +45,14 @@ int device_bind(struct udevice *parent, struct driver *drv,
  * tree.
  *
  * @parent: Pointer to device's parent
+ * @pre_reloc_only: If true, bind the driver only if its DM_INIT_F flag is set.
+ * If false bind the driver always.
  * @info: Name and platdata for this device
  * @devp: Returns a pointer to the bound device
  * @return 0 if OK, -ve on error
  */
-int device_bind_by_name(struct udevice *parent, const struct driver_info *info,
-			struct udevice **devp);
+int device_bind_by_name(struct udevice *parent, bool pre_reloc_only,
+			const struct driver_info *info, struct udevice **devp);
 
 /**
  * device_probe() - Probe a device, activating it
diff --git a/include/dm/device.h b/include/dm/device.h
index ae75a3f..4679979 100644
--- a/include/dm/device.h
+++ b/include/dm/device.h
@@ -23,6 +23,9 @@ struct driver_info;
 /* DM is responsible for allocating and freeing platdata */
 #define DM_FLAG_ALLOC_PDATA	(1 << 1)
 
+/* DM should init this device prior to relocation */
+#define DM_FLAG_PRE_RELOC	(1 << 2)
+
 /**
  * struct udevice - An instance of a driver
  *
@@ -117,6 +120,7 @@ struct udevice_id {
  * ops: Driver-specific operations. This is typically a list of function
  * pointers defined by the driver, to implement driver functions required by
  * the uclass.
+ * @flags: driver flags - see DM_FLAGS_...
  */
 struct driver {
 	char *name;
@@ -130,6 +134,7 @@ struct driver {
 	int priv_auto_alloc_size;
 	int platdata_auto_alloc_size;
 	const void *ops;	/* driver-specific operations */
+	uint32_t flags;
 };
 
 /* Declare a new U-Boot driver */
diff --git a/include/dm/lists.h b/include/dm/lists.h
index 49d87e6..87a3af5 100644
--- a/include/dm/lists.h
+++ b/include/dm/lists.h
@@ -42,7 +42,7 @@ struct uclass_driver *lists_uclass_lookup(enum uclass_id id);
  * @early_only: If true, bind only drivers with the DM_INIT_F flag. If false
  * bind all drivers.
  */
-int lists_bind_drivers(struct udevice *parent);
+int lists_bind_drivers(struct udevice *parent, bool pre_reloc_only);
 
 /**
  * lists_bind_fdt() - bind a device tree node
diff --git a/include/dm/root.h b/include/dm/root.h
index 35818b1..d37b452 100644
--- a/include/dm/root.h
+++ b/include/dm/root.h
@@ -26,9 +26,11 @@ struct udevice *dm_root(void);
  *
  * This scans all available platdata and creates drivers for each
  *
+ * @pre_reloc_only: If true, bind only drivers with the DM_FLAG_PRE_RELOC
+ * flag. If false bind all drivers.
  * @return 0 if OK, -ve on error
  */
-int dm_scan_platdata(void);
+int dm_scan_platdata(bool pre_reloc_only);
 
 /**
  * dm_scan_fdt() - Scan the device tree and bind drivers
@@ -36,9 +38,11 @@ int dm_scan_platdata(void);
  * This scans the device tree and creates a driver for each node
  *
  * @blob: Pointer to device tree blob
+ * @pre_reloc_only: If true, bind only drivers with the DM_FLAG_PRE_RELOC
+ * flag. If false bind all drivers.
  * @return 0 if OK, -ve on error
  */
-int dm_scan_fdt(const void *blob);
+int dm_scan_fdt(const void *blob, bool pre_reloc_only);
 
 /**
  * dm_init() - Initialise Driver Model structures