Re: [PATCH v10 3/3] drm/mediatek: Implement OF graphs support for display paths

AngeloGioacchino Del Regno
2024-10-04T10:39:48Z

Il 04/10/24 08:03, CK Hu (胡俊光) ha scritto:
> Hi, Angelo:
>
> On Tue, 2024-10-01 at 13:33 +0200, AngeloGioacchino Del Regno wrote:
>> Il 01/10/24 12:07, CK Hu (胡俊光) ha scritto:
>>> Hi, Angelo:
>>>
>>> On Tue, 2024-09-10 at 10:51 +0000, 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;
>>>> +
>>>> + /*
>>>> + * ETHDR and Padding are used exclusively in OVL Adaptor: if this
>>>> + * component is not one of those, it's likely not an OVL Adaptor path.
>>>> + */
>>>
>>> I don't know your logic here.
>>> The OVL Adaptor pipeline is:
>>>
>>> mdp_rdma -> padding ---+ +-------+
>>> Merge -> | |
>>> mdp_rdma -> padding ---+ | |
>>> | |
>>> mdp_rdma -> padding ---+ | |
>>> Merge -> | |
>>> mdp_rdma -> padding ---+ | |
>>> | ETHDR |
>>> mdp_rdma -> padding ---+ | |
>>> Merge -> | |
>>> mdp_rdma -> padding ---+ | |
>>> | |
>>> mdp_rdma -> padding ---+ | |
>>> Merge -> | |
>>> mdp_rdma -> padding ---+ +-------+
>>>
>>> So mdp_rdma and merge is not OVL Adaptor?
>>>
>>
>> Yes, and in device tree, you express that exactly like you just pictured.
>>
>> OVL Adaptor is treated like a software component internally, and manages
>> its own merge pipes exactly like before this commit.
>>
>> In case there will be any need to express OVL Adaptor as hardware component,
>> it will be possible to do so with no modification to the bindings.
>>
>>>
>>>> + return type == OVL_ADAPTOR_TYPE_ETHDR || type == OVL_ADAPTOR_TYPE_PADDING;
>>>> +}
>>>> +
>>>>
>>>
>>> [snip]
>>>
>>>> +
>>>> +/**
>>>> + * 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) {
>>>
>>> mdp_rdma would not be DDP_COMPONENT_DRM_OVL_ADAPTOR.
>>
>> This piece of code just avoids adding OVL_ADAPTOR more than once to the pipeline.
>>
>>>
>>>> + 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) {
>>>
>>> merge would not be DDP_COMPONENT_DRM_OVL_ADAPTOR.
>>> Finally, the path would be:
>>>
>>> mdp_rdma -> ovl adaptor (padding) -> merge -> (ethdr is skipped here) ...
>>>
>>
>> Again, the path in the OF graph is expressed exactly like you said.
>
> I know the OF graph is expressed like I said.
> But I care about the path in driver should like this:

Ok, now I understand your concern.

>
> static const unsigned int mt8195_mtk_ddp_ext[] = {
> DDP_COMPONENT_DRM_OVL_ADAPTOR,
> DDP_COMPONENT_MERGE5,
> DDP_COMPONENT_DP_INTF1,
> };
>
> In OF graph, the first component is mdp_rdma and mtk_ovl_adaptor_is_comp_present() would return false for mdp_rdma.
> So I think this would make mtk_drm_of_ddp_path_build_one() return error and the path is not created.
> If I'm wrong, please explain how this code would result in the path like mt8195_mtk_ddp_ext[].
>

The MDP_RDMA usage in mtk_disp_ovl_adaptor is hardcoded: in function
mtk_ovl_adaptor_layer_config(), the rdma_l/r are always OVL_ADAPTOR_MDP_RDMAx,
then function mtk_ovl_adaptor_dma_dev_get(), always returns the MDP_RDMA0
component, same for mtk_ovl_adaptor_get_{num_formats,formats}() which always
call mtk_mdp_rdma_get_formats() for OVL_ADAPTOR_MDP_RDMA0.

I have just rechecked how I expressed the path for MT8195 Tomato, where the
external display works with OF Graphs, and it was missing MDP_RDMA entirely.

The path was ethdr -> merge -> dp_intf1 ... and it should be mdp_rdma -> (etc).

Effectively, that is indeed wrong, as all of the steps must be expressed
inside of the graph.

Since the OVL Adaptor's RDMA instances' compatible strings do *not* collide
with the others, as OVL Adaptor uses compatible mediatek,mt8195-vdo1-rdma,
and the regular one uses compatible mediatek,mt8195-disp-rdma, we can resolve
this issue by changing function mtk_ovl_adaptor_is_comp_present()

from

return type == OVL_ADAPTOR_TYPE_ETHDR || type == OVL_ADAPTOR_TYPE_PADDING;

to

return type == OVL_ADAPTOR_TYPE_ETHDR || type == OVL_ADAPTOR_TYPE_PADDING ||
type == OVL_ADAPTOR_TYPE_MDP_RDMA;

is that okay for you?

> If you does not test this with mt8195 external display path, maybe we could just drop the code about OVL adaptor with a TODO comment.
>

And yes, as I said, external display paths were tested on 8195, actually both
on Kontron i1200 by Michael Walle and on MT8195 Tomato by myself.

Thanks again,
Angelo

> Regards,
> CK
>
>>
>> Regards,
>> Angelo
>>
>>> Regards,
>>> CK
>>>
>>>> + 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 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;
>>>> +}
>>>> +
>>
>>
>>

--
AngeloGioacchino Del Regno
Senior Software Engineer

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