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Subject: Re: [resend PATCH v4 4/5] drm/mediatek: Add support for mmsys through
 a pdev
From:   Matthias Brugger <matthias.bgg@gmail.com>
To:     Sean Wang <sean.wang@mediatek.com>, matthias.bgg@kernel.org
Cc:     ulrich.hecht+renesas@gmail.com, laurent.pinchart@ideasonboard.com,
        ck.hu@mediatek.com, p.zabel@pengutronix.de, airlied@linux.ie,
        robh+dt@kernel.org, mark.rutland@arm.com, mturquette@baylibre.com,
        sboyd@codeaurora.org, lee.jones@linaro.org, davem@davemloft.net,
        gregkh@linuxfoundation.org, mchehab@kernel.org,
        rdunlap@infradead.org, pi-cheng.chen@linaro.org,
        linux-clk@vger.kernel.org, linux@armlinux.org.uk,
        dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org,
        linux-mediatek@lists.infradead.org,
        Matthias Brugger <mbrugger@suse.com>
References: <20180717220328.792-1-matthias.bgg@kernel.org>
 <20180717220328.792-5-matthias.bgg@kernel.org>
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Message-ID: <660471a0-480b-241f-8880-8b56aed3e64b@gmail.com>
Date:   Wed, 18 Jul 2018 09:28:25 +0200
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On 18/07/18 09:27, Matthias Brugger wrote:
> Hi Sean,
> 
> On 18/07/18 04:57, Sean Wang wrote:
>> On Wed, 2018-07-18 at 00:03 +0200, matthias.bgg@kernel.org wrote:
>>> From: Matthias Brugger <mbrugger@suse.com>
>>>
>>> The MMSYS subsystem includes clocks and drm components.
>>> This patch adds an initailization path through a platform device
>>> for the clock part, so that both drivers get probed from the same
>>> device tree compatible.
>>>
>>
>> Sorry for that I should have a response earlier for the series.
>>
>> Some points I felt they're not exactly right and should be fixed up
>> before we're moving on
>>
>> Currently, drm driver have a wrong reference to the dt-binding,
>> "mediatek,mt2701-mmsys" or "mediatek,mt8173-mmsys", they should be all
>> for the subsystem exporting clock and reset line such common resource to
>> its sub-devices. Every subsystem has a similar shape. I hope mmsys
>> shouldn't be an exception.
> 
> I'm not sure if I understand what you mean. You proposed to use a platform
> device [1] and now you say we should change the DTS?
> 
> What do you mean by "drm driver has a wrong reference to the dt-binding"? How
> would you want to name it and most important, what would be your approach to
> have backwards compatibility to older device tree bindings?
> 

I forgot the reference:
[1] https://patchwork.kernel.org/patch/10367797/

>>
>> DRM device needs to have its own dt-binding show how connections between
>> DRM components being made and its node should be put under mmsys node.
>>> In this way, it becomes easy to see how the topology of the subsystem is
>> and grows, like a tree "device tree", instead of hiding the details in
>> the implementation.
>>
>> The similar example we already did for audsys on mt2701 and mt7623 as
>> below
>>
>> 	audsys: clock-controller@11220000 {
>> 		compatible = "mediatek,mt7623-audsys",
>> 			     "mediatek,mt2701-audsys",
>> 			     "syscon";
>> 			...
>>
>> 		afe: audio-controller {
>> 			compatible = "mediatek,mt7623-audio",
>> 				     "mediatek,mt2701-audio";
>> 			
>> 			...
>> 		};
>> 	};
>>
> 
> I think this approach is not working as, due to backwards compatibility, we have
> to make sure that the DRM driver gets probed with the mmsys binding.
> 
> Regards,
> Matthias
> 
>> 	
>> 	Sean
>>
>>
>>> Signed-off-by: Matthias Brugger <mbrugger@suse.com>
>>> ---
>>>  drivers/gpu/drm/mediatek/mtk_drm_drv.c | 18 ++++++++++++++++++
>>>  drivers/gpu/drm/mediatek/mtk_drm_drv.h |  2 ++
>>>  2 files changed, 20 insertions(+)
>>>
>>> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.c b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
>>> index dd249cf5121e..c946aea722e5 100644
>>> --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.c
>>> +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.c
>>> @@ -173,6 +173,7 @@ static const struct mtk_mmsys_driver_data mt2701_mmsys_driver_data = {
>>>  	.ext_path = mt2701_mtk_ddp_ext,
>>>  	.ext_len = ARRAY_SIZE(mt2701_mtk_ddp_ext),
>>>  	.shadow_register = true,
>>> +	.clk_drv_name = "clk-mt2701-mm",
>>>  };
>>>  
>>>  static const struct mtk_mmsys_driver_data mt8173_mmsys_driver_data = {
>>> @@ -180,6 +181,7 @@ static const struct mtk_mmsys_driver_data mt8173_mmsys_driver_data = {
>>>  	.main_len = ARRAY_SIZE(mt8173_mtk_ddp_main),
>>>  	.ext_path = mt8173_mtk_ddp_ext,
>>>  	.ext_len = ARRAY_SIZE(mt8173_mtk_ddp_ext),
>>> +	.clk_drv_name = "clk-mt8173-mm",
>>>  };
>>>  
>>>  static int mtk_drm_kms_init(struct drm_device *drm)
>>> @@ -411,6 +413,19 @@ static int mtk_drm_probe(struct platform_device *pdev)
>>>  	if (IS_ERR(private->config_regs))
>>>  		return PTR_ERR(private->config_regs);
>>>  
>>> +	if (private->data->clk_drv_name) {
>>> +		private->clk_dev = platform_device_register_data(dev,
>>> +						private->data->clk_drv_name, -1,
>>> +						NULL, 0);
>>> +
>>> +		if (IS_ERR(private->clk_dev)) {
>>> +			pr_err("failed to register %s platform device\n",
>>> +						private->data->clk_drv_name);
>>> +
>>> +			return PTR_ERR(private->clk_dev);
>>> +		}
>>> +	}
>>> +
>>>  	/* Iterate over sibling DISP function blocks */
>>>  	for_each_child_of_node(dev->of_node->parent, node) {
>>>  		const struct of_device_id *of_id;
>>> @@ -515,6 +530,9 @@ static int mtk_drm_remove(struct platform_device *pdev)
>>>  	for (i = 0; i < DDP_COMPONENT_ID_MAX; i++)
>>>  		of_node_put(private->comp_node[i]);
>>>  
>>> +	if (private->clk_dev)
>>> +		platform_device_unregister(private->clk_dev);
>>> +
>>>  	return 0;
>>>  }
>>>  
>>> diff --git a/drivers/gpu/drm/mediatek/mtk_drm_drv.h b/drivers/gpu/drm/mediatek/mtk_drm_drv.h
>>> index 86cec19193c4..200eee5de419 100644
>>> --- a/drivers/gpu/drm/mediatek/mtk_drm_drv.h
>>> +++ b/drivers/gpu/drm/mediatek/mtk_drm_drv.h
>>> @@ -34,11 +34,13 @@ struct mtk_mmsys_driver_data {
>>>  	const enum mtk_ddp_comp_id *ext_path;
>>>  	unsigned int ext_len;
>>>  	bool shadow_register;
>>> +	const char *clk_drv_name;
>>>  };
>>>  
>>>  struct mtk_drm_private {
>>>  	struct drm_device *drm;
>>>  	struct device *dma_dev;
>>> +	struct platform_device *clk_dev;
>>>  
>>>  	unsigned int num_pipes;
>>>  
>>
>>