[PATCH v5 4/6] drm: Allow DSI devices to be registered before the host registers.

[Eric Anholt]

When a mipi_dsi_host is registered, the DT is walked to find any child
nodes with compatible strings.  Those get registered as DSI devices,
and most DSI panel drivers are mipi_dsi_drivers that attach to those nodes.

There is one special case currently, the adv7533 bridge, where the
bridge probes on I2C, and during the bridge attach step it looks up
the mipi_dsi_host and registers the mipi_dsi_device (for its own stub
mipi_dsi_driver).

For the Raspberry Pi panel, though, we also need to attach on I2C (our
control bus), but don't have a bridge driver.  The lack of a bridge's
attach() step like adv7533 uses means that we aren't able to delay the
mipi_dsi_device creation until the mipi_dsi_host is present.

To fix this, we extend mipi_dsi_device_register_full() to allow being
called with a NULL host, which puts the device on a queue waiting for
a host to appear.  When a new host is registered, we fill in the host
value and finish the device creation process.

v2: Cleanly error out if one attempts to mipi_dsi_attach() without a
    host.  Fix handling of DSI with multiple devices, and OF node
    refcounting.

Signed-off-by: Eric Anholt <eric@xxxxxxxxxx>
---
 drivers/gpu/drm/drm_mipi_dsi.c | 63 ++++++++++++++++++++++++++++++++++--------
 include/drm/drm_mipi_dsi.h     |  3 ++
 2 files changed, 54 insertions(+), 12 deletions(-)

diff --git a/drivers/gpu/drm/drm_mipi_dsi.c b/drivers/gpu/drm/drm_mipi_dsi.c
index 1160a579e0dc..77d439254da6 100644
--- a/drivers/gpu/drm/drm_mipi_dsi.c
+++ b/drivers/gpu/drm/drm_mipi_dsi.c
@@ -45,6 +45,13 @@
  * subset of the MIPI DCS command set.
  */
 
+static DEFINE_MUTEX(host_lock);
+static LIST_HEAD(host_list);
+/* List of struct mipi_dsi_device which were registered while no host
+ * was available.
+ */
+static LIST_HEAD(unattached_device_list);
+
 static int mipi_dsi_device_match(struct device *dev, struct device_driver *drv)
 {
 	struct mipi_dsi_device *dsi = to_mipi_dsi_device(dev);
@@ -138,10 +145,12 @@ static struct mipi_dsi_device *mipi_dsi_device_alloc(struct mipi_dsi_host *host)
 
 	dsi->host = host;
 	dsi->dev.bus = &mipi_dsi_bus_type;
-	dsi->dev.parent = host->dev;
 	dsi->dev.type = &mipi_dsi_device_type;
 
-	device_initialize(&dsi->dev);
+	if (dsi->host) {
+		dsi->dev.parent = host->dev;
+		device_initialize(&dsi->dev);
+	}
 
 	return dsi;
 }
@@ -206,7 +215,7 @@ mipi_dsi_device_register_full(struct mipi_dsi_host *host,
 			      const struct mipi_dsi_device_info *info)
 {
 	struct mipi_dsi_device *dsi;
-	struct device *dev = host->dev;
+	struct device *dev = host ? host->dev : NULL;
 	int ret;
 
 	if (!info) {
@@ -230,11 +239,17 @@ mipi_dsi_device_register_full(struct mipi_dsi_host *host,
 	dsi->channel = info->channel;
 	strlcpy(dsi->name, info->type, sizeof(dsi->name));
 
-	ret = mipi_dsi_device_add(dsi);
-	if (ret) {
-		dev_err(dev, "failed to add DSI device %d\n", ret);
-		kfree(dsi);
-		return ERR_PTR(ret);
+	if (!dsi->host) {
+		mutex_lock(&host_lock);
+		list_add(&dsi->list, &unattached_device_list);
+		mutex_unlock(&host_lock);
+	} else {
+		ret = mipi_dsi_device_add(dsi);
+		if (ret) {
+			dev_err(dev, "failed to add DSI device %d\n", ret);
+			kfree(dsi);
+			return ERR_PTR(ret);
+		}
 	}
 
 	return dsi;
@@ -251,9 +266,6 @@ void mipi_dsi_device_unregister(struct mipi_dsi_device *dsi)
 }
 EXPORT_SYMBOL(mipi_dsi_device_unregister);
 
-static DEFINE_MUTEX(host_lock);
-static LIST_HEAD(host_list);
-
 /**
  * of_find_mipi_dsi_host_by_node() - find the MIPI DSI host matching a
  *				     device tree node
@@ -285,6 +297,7 @@ EXPORT_SYMBOL(of_find_mipi_dsi_host_by_node);
 int mipi_dsi_host_register(struct mipi_dsi_host *host)
 {
 	struct device_node *node;
+	struct mipi_dsi_device *dsi, *temp;
 
 	for_each_available_child_of_node(host->dev->of_node, node) {
 		/* skip nodes without reg property */
@@ -295,6 +308,27 @@ int mipi_dsi_host_register(struct mipi_dsi_host *host)
 
 	mutex_lock(&host_lock);
 	list_add_tail(&host->list, &host_list);
+
+	/* If any DSI devices were registered under our OF node, then
+	 * connect our host to it and probe them now.
+	 */
+	list_for_each_entry_safe(dsi, temp, &unattached_device_list, list) {
+		struct device_node *host_node = of_get_parent(dsi->dev.of_node);
+
+		if (!of_node_cmp(host_node->name, "ports"))
+			host_node = of_get_next_parent(host_node);
+
+		if (host_node == host->dev->of_node) {
+			dsi->host = host;
+			dsi->dev.parent = host->dev;
+			device_initialize(&dsi->dev);
+
+			mipi_dsi_device_add(dsi);
+			list_del_init(&dsi->list);
+		}
+
+		of_node_put(host_node);
+	}
 	mutex_unlock(&host_lock);
 
 	return 0;
@@ -326,7 +360,12 @@ EXPORT_SYMBOL(mipi_dsi_host_unregister);
  */
 int mipi_dsi_attach(struct mipi_dsi_device *dsi)
 {
-	const struct mipi_dsi_host_ops *ops = dsi->host->ops;
+	const struct mipi_dsi_host_ops *ops;
+
+	if (!dsi->host)
+		return -EINVAL;
+
+	ops = dsi->host->ops;
 
 	if (!ops || !ops->attach)
 		return -ENOSYS;
diff --git a/include/drm/drm_mipi_dsi.h b/include/drm/drm_mipi_dsi.h
index 4fef19064b0f..dfe640fec9ba 100644
--- a/include/drm/drm_mipi_dsi.h
+++ b/include/drm/drm_mipi_dsi.h
@@ -168,6 +168,7 @@ struct mipi_dsi_device_info {
  * @format: pixel format for video mode
  * @lanes: number of active data lanes
  * @mode_flags: DSI operation mode related flags
+ * @list: Entry on the unattached_device_list
  */
 struct mipi_dsi_device {
 	struct mipi_dsi_host *host;
@@ -178,6 +179,8 @@ struct mipi_dsi_device {
 	unsigned int lanes;
 	enum mipi_dsi_pixel_format format;
 	unsigned long mode_flags;
+
+	struct list_head list;
 };
 
 #define MIPI_DSI_MODULE_PREFIX "mipi-dsi:"
-- 
2.11.0