diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c index 79d8a0319e71..d4e80d720361 100644 --- a/drivers/gpu/drm/sun4i/sun4i_tcon.c +++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c @@ -463,8 +463,9 @@ static int sun4i_tcon_init_regmap(struct device *dev, * function in fact searches the corresponding engine, and the ID is * requested via the get_id function of the engine. */ -static struct sunxi_engine *sun4i_tcon_find_engine(struct sun4i_drv *drv, - struct device_node *node) +static struct sunxi_engine * +sun4i_tcon_find_engine_traverse(struct sun4i_drv *drv, + struct device_node *node) { struct device_node *port, *ep, *remote; struct sunxi_engine *engine; @@ -502,7 +503,7 @@ static struct sunxi_engine *sun4i_tcon_find_engine(struct sun4i_drv *drv, } /* keep looking through upstream ports */ - engine = sun4i_tcon_find_engine(drv, remote); + engine = sun4i_tcon_find_engine_traverse(drv, remote); if (!IS_ERR(engine)) { of_node_put(remote); of_node_put(port); @@ -513,6 +514,120 @@ static struct sunxi_engine *sun4i_tcon_find_engine(struct sun4i_drv *drv, return ERR_PTR(-EINVAL); } +/* + * The device tree binding says that the remote endpoint ID of any + * connection between components, up to and including the TCON, of + * the display pipeline should be equal to the actual ID of the local + * component. Thus we can look at any one of the input connections of + * the TCONs, and use that connection's remote endpoint ID as our own. + * + * Since the user of this function already finds the input port, + * the port is passed in directly without further checks. + */ +static int sun4i_tcon_of_get_id_from_port(struct device_node *port) +{ + struct device_node *ep; + int ret = -EINVAL; + + /* try finding an upstream endpoint */ + for_each_available_child_of_node(port, ep) { + struct device_node *remote; + u32 reg; + + remote = of_graph_get_remote_endpoint(ep); + if (!remote) + continue; + + ret = of_property_read_u32(remote, "reg", ®); + if (ret) + continue; + + ret = reg; + } + + return ret; +} + +/* + * Once we know the TCON's id, we can look through the list of + * engines to find a matching one. We assume all engines have + * been probed and added to the list. + */ +static struct sunxi_engine *sun4i_tcon_get_engine_by_id(struct sun4i_drv *drv, + int id) +{ + struct sunxi_engine *engine; + + list_for_each_entry(engine, &drv->engine_list, list) + if (engine->id == id) + return engine; + + return ERR_PTR(-EINVAL); +} + +/* + * On SoCs with the old display pipeline design (Display Engine 1.0), + * we assumed the TCON was always tied to just one backend. However + * this proved not to be the case. On the A31, the TCON can select + * either backend as its source. On the A20 (and likely on the A10), + * the backend can choose which TCON to output to. + * + * The device tree binding says that the remote endpoint ID of any + * connection between components, up to and including the TCON, of + * the display pipeline should be equal to the actual ID of the local + * component. Thus we should be able to look at any one of the input + * connections of the TCONs, and use that connection's remote endpoint + * ID as our own. + * + * However the connections between the backend and TCON were assumed + * to be always singular, and their endpoit IDs were all incorrectly + * set to 0. This means for these old device trees, we cannot just look + * up the remote endpoint ID of a TCON input endpoint. TCON1 would be + * incorrectly identified as TCON0. + * + * This function first checks if the TCON node has 2 input endpoints. + * If so, then the device tree is a corrected version, and it will use + * sun4i_tcon_of_get_id() and sun4i_tcon_get_engine_by_id() from above + * to fetch the ID and engine directly. If not, then it is likely an + * old device trees, where the endpoint IDs were incorrect, but did not + * have endpoint connections between the backend and TCON across + * different display pipelines. It will fall back to the old method of + * traversing the of_graph to try and find a matching engine by device + * node. + * + * In the case of single display pipeline device trees, either method + * works. + */ +static struct sunxi_engine *sun4i_tcon_find_engine(struct sun4i_drv *drv, + struct device_node *node) +{ + struct device_node *port; + struct sunxi_engine *engine; + + port = of_graph_get_port_by_id(node, 0); + if (!port) + return ERR_PTR(-EINVAL); + + /* + * Is this a corrected device tree with cross pipeline + * connections between the backend and TCON? + */ + if (of_get_child_count(port) > 1) { + /* Get our ID directly from an upstream endpoint */ + int id = sun4i_tcon_of_get_id_from_port(port); + + /* Get our engine by matching our ID */ + engine = sun4i_tcon_get_engine_by_id(drv, id); + + of_node_put(port); + return engine; + } + + /* Fallback to old method by traversing input endpoints */ + of_node_put(port); + return sun4i_tcon_find_engine_traverse(drv, node); +} + static int sun4i_tcon_bind(struct device *dev, struct device *master, void *data) {