Message-ID: <6415a3a1-f00d-428e-b607-ae27ac63c11a@collabora.com>
Date: Tue, 8 Oct 2024 10:03:10 +0200
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: CK Hu (胡俊光) <ck.hu@...iatek.com>,
 "chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>
Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
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 "sui.jingfeng@...ux.dev" <sui.jingfeng@...ux.dev>,
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 "linux-arm-kernel@...ts.infradead.org"
 <linux-arm-kernel@...ts.infradead.org>,
 Alexandre Mergnat <amergnat@...libre.com>
Subject: Re: [PATCH v11 3/3] drm/mediatek: Implement OF graphs support for
 display paths

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@...libre.com>
>> Tested-by: Alexandre Mergnat <amergnat@...libre.com>
>> Acked-by: Sui Jingfeng <sui.jingfeng@...ux.dev>
>> Tested-by: Michael Walle <mwalle@...nel.org> # on kontron-sbc-i1200
>> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
>> ---
> 
> [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@mediatek.com/

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

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;
>> +}
>> +

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