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

AngeloGioacchino Del Regno
2024-10-14T08:45:02Z

Il 14/10/24 10:19, CK Hu (胡俊光) ha scritto:
> 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@baylibre.com>
>>>>>> Tested-by: Alexandre Mergnat <amergnat@baylibre.com>
>>>>>> Acked-by: Sui Jingfeng <sui.jingfeng@linux.dev>
>>>>>> Tested-by: Michael Walle <mwalle@kernel.org> # on kontron-sbc-i1200
>>>>>> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.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
>

Yes.

> So the path would be
>
> ovl_adaptor -> merge5.
>

Yes, exactly!

> 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@mediatek.com>

Thank you! :-)

Cheers,
Angelo

>
>>
>> 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;
>>>>>> +}
>>>>>> +
>>>>
>>>>
>>
>>