Message-ID: <39090cb8ea0468252e53712553d483b696d83754.camel@mediatek.com>
Date: Mon, 14 Oct 2024 08:19:51 +0000
From: CK Hu (胡俊光) <ck.hu@...iatek.com>
To: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	"chunkuang.hu@...nel.org" <chunkuang.hu@...nel.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-mediatek@...ts.infradead.org" <linux-mediatek@...ts.infradead.org>,
	"sui.jingfeng@...ux.dev" <sui.jingfeng@...ux.dev>, "wenst@...omium.org"
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	Yu-chang Lee (李禹璋) <Yu-chang.Lee@...iatek.com>,
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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

Hi, Angelo:

On Wed, 2024-10-09 at 12:10 +0200, AngeloGioacchino Del Regno wrote:
> 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.

For "*temporarily omitted* in the graph for MT8195", do you mean the OF graph is

mdp_rdma (0 ~ 7) -> padding (0 ~ 7) -> ethdr -> merge5

So the path would be

ovl_adaptor -> merge5.

So this patch work fine depending on the tricky way of OF graph.
Add comment to describe the tricky way of OF graph. After this,

Reviewed-by: CK Hu <ck.hu@...iatek.com>

> 
> 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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