Message-ID: <0dca529a-85f2-4ed3-b3f4-132e6b233f5c@collabora.com>
Date: Wed, 9 Oct 2024 12:10:24 +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 09/10/24 10:43, CK Hu (胡俊光) ha scritto:
> Hi, Angelo:
> 
> On Tue, 2024-10-08 at 10:03 +0200, AngeloGioacchino Del Regno wrote:
>> 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.
> 
> In [1] & [2], I want the path to be like mt8195_mtk_ddp_ext[]. I don't know where is the contradiction?
> mt8195_mtk_ddp_ext[] is:
> 
> ovl_adaptor -> merge5
> 
> but this patch generate the path as
> 
> ovl_adaptor -> merge (1 ~ 4) -> merge5
> 
> it's not the same and this may cause something wrong.
> I'm sorry my expression make you confused.
> So what I want is to generate the path as
> 
> ovl_adaptor -> merge5

Ah, okay, no - you're misunderstanding how the OVL_ADAPTOR is treated here, hence
we misunderstood each other in the end!

The resulting path in mt8195_mtk_ddp_ext[] will be ovl_adaptor->merge5, because
the merge1-4 are already taken dynamically by the ovl_adaptor driver so these
will be *temporarily omitted* in the graph for MT8195.

My intention is to add handling for the additional merge1-4 (and similar) selection
with OF Graph support *later*, not in this series (please be aware that it will
*not be needed* to change any bindings, and compatibility will be guaranteed with
no additional effort).

This is because I believe that the ovl_adaptor driver needs more changes than just
a basic OF Graph implementation: as of now, that driver is practically specific to
just MT8195 and MT8188, as the OVL_ADAPTOR specific MERGE paths are hardcoded.

So, I am planning to improve the ovl_adaptor driver, but that will be a separated
series as it's probably going to be a relatively (in relation to the size of the
ovl_adaptor driver) big set of changes.

Regards,
Angelo

> 
> Regards,
> CK
> 
>>
>> [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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