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Subject: Re: [resend PATCH v4 4/5] drm/mediatek: Add support for mmsys through
 a pdev
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>
 <1531882655.8953.83.camel@mtkswgap22>
From:   Matthias Brugger <matthias.bgg@gmail.com>
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Message-ID: <50c93f6d-c546-1479-62c1-adc0b40d5dab@gmail.com>
Date:   Wed, 18 Jul 2018 09:27:48 +0200
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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?

> 
> 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;
>>  
> 
>