linux-kernel - Re: [PATCH v7 3/3] drm/mediatek: Implement OF graphs support for display paths

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Date: Tue, 18 Jun 2024 12:12:00 +0200
From: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
To: Michael Walle <michael@...le.cc>, chunkuang.hu@...nel.org
Cc: robh@...nel.org, krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
 p.zabel@...gutronix.de, airlied@...il.com, daniel@...ll.ch,
 maarten.lankhorst@...ux.intel.com, mripard@...nel.org, tzimmermann@...e.de,
 matthias.bgg@...il.com, shawn.sung@...iatek.com, yu-chang.lee@...iatek.com,
 ck.hu@...iatek.com, jitao.shi@...iatek.com, devicetree@...r.kernel.org,
 linux-kernel@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 linux-mediatek@...ts.infradead.org, linux-arm-kernel@...ts.infradead.org,
 wenst@...omium.org, kernel@...labora.com, sui.jinfeng@...ux.dev,
 Alexandre Mergnat <amergnat@...libre.com>
Subject: Re: [PATCH v7 3/3] drm/mediatek: Implement OF graphs support for
 display paths

Il 17/06/24 15:24, Michael Walle ha scritto:
> Hi Angelo,
> 
>> +/**
>> + * 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_err(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);
>> +
>> +	/*
>> +	 * The device component might not be disabled: in that case, don't
> 
> Sorry there was a typo in my proposal, This should either be
> "not be enabled" or "be disabled".
> 

I even noticed the typo and fixed it, then sent the *not* fixed version. Argh.

>> +	 * check the last entry and just report that the device is missing.
>> +	 */
>> +	if (ret == -ENODEV)
>> +		return ret;
>> +
> 
> ..
> 
>> +static int mtk_drm_of_ddp_path_build(struct device *dev, struct device_node *node,
>> +				     struct mtk_mmsys_driver_data *data)
>> +{
>> +	struct device_node *ep_node;
>> +	struct of_endpoint of_ep;
>> +	bool output_present[MAX_CRTC] = { false };
>> +	bool valid_output_found = false;
>> +	int ret;
>> +
>> +	for_each_endpoint_of_node(node, ep_node) {
>> +		ret = of_graph_parse_endpoint(ep_node, &of_ep);
>> +		if (ret) {
>> +			dev_err_probe(dev, ret, "Cannot parse endpoint\n");
>> +			break;
>> +		}
>> +
>> +		if (of_ep.id >= MAX_CRTC) {
>> +			ret = dev_err_probe(dev, -EINVAL,
>> +					    "Invalid endpoint%u number\n", of_ep.port);
>> +			break;
>> +		}
>> +
>> +		output_present[of_ep.id] = true;
>> +	}
>> +
>> +	if (ret) {
>> +		of_node_put(ep_node);
>> +		return ret;
>> +	}
>> +
>> +	if (output_present[CRTC_MAIN]) {
>> +		ret = mtk_drm_of_ddp_path_build_one(dev, CRTC_MAIN,
>> +						    &data->main_path, &data->main_len);
>> +		if (ret == 0)
>> +			valid_output_found = true;
>> +		else if (ret != -ENODEV)
>> +			return ret;
>> +	}
>> +
>> +	if (output_present[CRTC_EXT]) {
>> +		ret = mtk_drm_of_ddp_path_build_one(dev, CRTC_EXT,
>> +						    &data->ext_path, &data->ext_len);
>> +		if (ret == 0)
>> +			valid_output_found = true;
>> +		else if (ret != -ENODEV)
>> +			return ret;
>> +	}
>> +
>> +	if (output_present[CRTC_THIRD]) {
>> +		ret = mtk_drm_of_ddp_path_build_one(dev, CRTC_THIRD,
>> +						    &data->third_path, &data->third_len);
>> +		if (ret == 0)
>> +			valid_output_found = true;
>> +		else if (ret != -ENODEV)
>> +			return ret;
>> +	}
>> +
>> +	if (!valid_output_found)
>> +		return -ENODEV;
> 
> This doesn't work. My proposal just ignored the ENODEV error. Now
> you'll return ENODEV if there is no output for a given mmsys. In my
> case, that is true for the first mmsys. Subsequent mmsys's doesn't
> get probed in that case, it seems.
> 
> Anyway, you shouldn't return ENODEV here because disabled just
> means not available, i.e. it should be treated the same as
> "output_present[] == false".
> 

Right. Okay, v8 will fix that.

Thanks,
Angelo