Re: [PATCH v11 3/3] drm/mediatek: Implement OF graphs support for display paths

From: AngeloGioacchino Del Regno
Date: Tue Oct 08 2024 - 04:38:06 EST

Il 08/10/24 09:41, CK Hu (胡俊光) ha scritto:
Hi, Angelo:

On Mon, 2024-10-07 at 11:31 +0200, AngeloGioacchino Del Regno wrote:
It is impossible to add each and every possible DDP path combination
for each and every possible combination of SoC and board: right now,
this driver hardcodes configuration for 10 SoCs and this is going to
grow larger and larger, and with new hacks like the introduction of
mtk_drm_route which is anyway not enough for all final routes as the
DSI cannot be connected to MERGE if it's not a dual-DSI, or enabling
DSC preventively doesn't work if the display doesn't support it, or
others.

Since practically all display IPs in MediaTek SoCs support being
interconnected with different instances of other, or the same, IPs
or with different IPs and in different combinations, the final DDP
pipeline is effectively a board specific configuration.

Implement OF graphs support to the mediatek-drm drivers, allowing to
stop hardcoding the paths, and preventing this driver to get a huge
amount of arrays for each board and SoC combination, also paving the
way to share the same mtk_mmsys_driver_data between multiple SoCs,
making it more straightforward to add support for new chips.

Reviewed-by: Alexandre Mergnat <amergnat@xxxxxxxxxxxx>
Tested-by: Alexandre Mergnat <amergnat@xxxxxxxxxxxx>
Acked-by: Sui Jingfeng <sui.jingfeng@xxxxxxxxx>
Tested-by: Michael Walle <mwalle@xxxxxxxxxx> # on kontron-sbc-i1200
Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@xxxxxxxxxxxxx>
---

[snip]

+
+bool mtk_ovl_adaptor_is_comp_present(struct device_node *node)
+{
+ enum mtk_ovl_adaptor_comp_type type;
+ int ret;
+
+ ret = ovl_adaptor_of_get_ddp_comp_type(node, &type);
+ if (ret)
+ return false;
+
+ if (type >= OVL_ADAPTOR_TYPE_NUM)
+ return false;
+
+ /*
+ * In the context of mediatek-drm, ETHDR, MDP_RDMA and Padding are
+ * used exclusively by OVL Adaptor: if this component is not one of
+ * those, it's likely not an OVL Adaptor path.
+ */
+ return type == OVL_ADAPTOR_TYPE_ETHDR ||
+ type == OVL_ADAPTOR_TYPE_MDP_RDMA ||
+ type == OVL_ADAPTOR_TYPE_PADDING;
+}
+

[snip]

+
+static int mtk_drm_of_get_ddp_ep_cid(struct device_node *node,
+ int output_port, enum mtk_crtc_path crtc_path,
+ struct device_node **next, unsigned int *cid)
+{
+ struct device_node *ep_dev_node, *ep_out;
+ enum mtk_ddp_comp_type comp_type;
+ int ret;
+
+ ep_out = of_graph_get_endpoint_by_regs(node, output_port, crtc_path);
+ if (!ep_out)
+ return -ENOENT;
+
+ ep_dev_node = of_graph_get_remote_port_parent(ep_out);
+ of_node_put(ep_out);
+ if (!ep_dev_node)
+ return -EINVAL;
+
+ /*
+ * Pass the next node pointer regardless of failures in the later code
+ * so that if this function is called in a loop it will walk through all
+ * of the subsequent endpoints anyway.
+ */
+ *next = ep_dev_node;
+
+ if (!of_device_is_available(ep_dev_node))
+ return -ENODEV;
+
+ ret = mtk_drm_of_get_ddp_comp_type(ep_dev_node, &comp_type);
+ if (ret) {
+ if (mtk_ovl_adaptor_is_comp_present(ep_dev_node)) {
+ *cid = (unsigned int)DDP_COMPONENT_DRM_OVL_ADAPTOR;
+ return 0;
+ }
+ return ret;
+ }
+
+ ret = mtk_ddp_comp_get_id(ep_dev_node, comp_type);
+ if (ret < 0)
+ return ret;
+
+ /* All ok! Pass the Component ID to the caller. */
+ *cid = (unsigned int)ret;
+
+ return 0;
+}
+
+/**
+ * mtk_drm_of_ddp_path_build_one - Build a Display HW Pipeline for a CRTC Path
+ * @dev: The mediatek-drm device
+ * @cpath: CRTC Path relative to a VDO or MMSYS
+ * @out_path: Pointer to an array that will contain the new pipeline
+ * @out_path_len: Number of entries in the pipeline array
+ *
+ * MediaTek SoCs can use different DDP hardware pipelines (or paths) depending
+ * on the board-specific desired display configuration; this function walks
+ * through all of the output endpoints starting from a VDO or MMSYS hardware
+ * instance and builds the right pipeline as specified in device trees.
+ *
+ * Return:
+ * * %0 - Display HW Pipeline successfully built and validated
+ * * %-ENOENT - Display pipeline was not specified in device tree
+ * * %-EINVAL - Display pipeline built but validation failed
+ * * %-ENOMEM - Failure to allocate pipeline array to pass to the caller
+ */
+static int mtk_drm_of_ddp_path_build_one(struct device *dev, enum mtk_crtc_path cpath,
+ const unsigned int **out_path,
+ unsigned int *out_path_len)
+{
+ struct device_node *next, *prev, *vdo = dev->parent->of_node;
+ unsigned int temp_path[DDP_COMPONENT_DRM_ID_MAX] = { 0 };
+ unsigned int *final_ddp_path;
+ unsigned short int idx = 0;
+ bool ovl_adaptor_comp_added = false;
+ int ret;
+
+ /* Get the first entry for the temp_path array */
+ ret = mtk_drm_of_get_ddp_ep_cid(vdo, 0, cpath, &next, &temp_path[idx]);
+ if (ret) {
+ if (next && temp_path[idx] == DDP_COMPONENT_DRM_OVL_ADAPTOR) {
+ dev_dbg(dev, "Adding OVL Adaptor for %pOF\n", next);
+ ovl_adaptor_comp_added = true;
+ } else {
+ if (next)
+ dev_err(dev, "Invalid component %pOF\n", next);
+ else
+ dev_err(dev, "Cannot find first endpoint for path %d\n", cpath);
+
+ return ret;
+ }
+ }
+ idx++;
+
+ /*
+ * Walk through port outputs until we reach the last valid mediatek-drm component.
+ * To be valid, this must end with an "invalid" component that is a display node.
+ */
+ do {
+ prev = next;
+ ret = mtk_drm_of_get_ddp_ep_cid(next, 1, cpath, &next, &temp_path[idx]);
+ of_node_put(prev);
+ if (ret) {
+ of_node_put(next);
+ break;
+ }
+
+ /*
+ * If this is an OVL adaptor exclusive component and one of those
+ * was already added, don't add another instance of the generic
+ * DDP_COMPONENT_OVL_ADAPTOR, as this is used only to decide whether
+ * to probe that component master driver of which only one instance
+ * is needed and possible.
+ */
+ if (temp_path[idx] == DDP_COMPONENT_DRM_OVL_ADAPTOR) {
+ if (!ovl_adaptor_comp_added)
+ ovl_adaptor_comp_added = true;
+ else
+ idx--;
+ }
+ } while (++idx < DDP_COMPONENT_DRM_ID_MAX);

For the mt8195 external display path, the OF graph is

mdp_rdma (0 ~ 7) -> padding (0 ~ 7) -> merge (1 ~ 4) -> ethdr -> merge5

and this function would generate the path as

ovl_adaptor -> merge (1 ~ 4) -> merge 5

This is not what I expect.
Is any thing wrong with me?


I mean no offense, really, but your reply here is a contradiction...

In [1], you explained what the path for the external display should look like
and said that the graph in DT should generate a path which, in the driver, shall
look like the current mt8195_mtk_ddp_ext[] hardcoded array.

In [2], you repeated that you "just want the path to be like mt8195_mtk_ddp_ext[]".

Now you're saying that this is not what you expect.
I don't understand your intention.

[1]: https://lore.kernel.org/all/58ee09aeb5a224dbc8faee236ed1a77ce3fbd011.camel@xxxxxxxxxxxx/

[2]: https://lore.kernel.org/all/04f1506b23b41c775e0735b5b3189b4118500715.camel@xxxxxxxxxxxx/

Regards,
Angelo


+
+ /*
+ * The device component might not be enabled: in that case, don't
+ * check the last entry and just report that the device is missing.
+ */
+ if (ret == -ENODEV)
+ return ret;
+
+ /* If the last entry is not a final display output, the configuration is wrong */
+ switch (temp_path[idx - 1]) {
+ case DDP_COMPONENT_DP_INTF0:
+ case DDP_COMPONENT_DP_INTF1:
+ case DDP_COMPONENT_DPI0:
+ case DDP_COMPONENT_DPI1:
+ case DDP_COMPONENT_DSI0:
+ case DDP_COMPONENT_DSI1:
+ case DDP_COMPONENT_DSI2:
+ case DDP_COMPONENT_DSI3:
+ break;
+ default:
+ dev_err(dev, "Invalid display hw pipeline. Last component: %d (ret=%d)\n",
+ temp_path[idx - 1], ret);
+ return -EINVAL;
+ }
+
+ final_ddp_path = devm_kmemdup(dev, temp_path, idx * sizeof(temp_path[0]), GFP_KERNEL);
+ if (!final_ddp_path)
+ return -ENOMEM;
+
+ dev_dbg(dev, "Display HW Pipeline built with %d components.\n", idx);
+
+ /* Pipeline built! */
+ *out_path = final_ddp_path;
+ *out_path_len = idx;
+
+ return 0;
+}
+