Re: [resend PATCH v4 4/5] drm/mediatek: Add support for mmsys through a pdev

[Sean Wang <sean.wang@mediatek.com>]

On Wed, 2018-07-18 at 11:05 +0300, Laurent Pinchart wrote:
> Hi Sean,
> 
> On Wednesday, 18 July 2018 05:57:35 EEST 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.
> > 
> > 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";
> > 
> > 		
> 	...
> > 		
> };
> > 	};
> 
> This looks very strange to me. I'm not familiar with the hardware 
> architecture, but a clock controller that includes an audio controller seems 
> like a very weird design. It's usually the other way around, you have an audio

yes, naming audsys as clock controller is really not good. it should be
worth a better naming.

mtk subsystem AFAIK works as a container, at least provides clocks,
reset, syscon access, these common resource to these devices running on
the subsystem. It also has a power gate independent from other
subsystem, that can be controlled when these devices all powered down
or once up.

And it should be better that we don't assume what exact devices are
running on since it is possible that there're different devices running
on the same subsystem per SoC. mtk has many subsystem working in this
way. mmsys is just a case. we can see in [1]


[1]
https://elixir.bootlin.com/linux/v4.18-rc5/source/Documentation/devicetree/bindings/arm/mediatek
 
> controller, and it also contains hardware that produces clocks, and possibly 
> handles miscellaneous audio-related routing tasks. I would thus expect the 
> reverse in the device tree:
> 
> 	afe: audio-controller@11220000 {
> 		
> compatible = "mediatek,mt7623-audio",
> 		
> 	     "mediatek,mt2701-audio";
> 		
> ..
> 
> 		
> audsys: clock-controller {
> 		
> 	compatible = "mediatek,mt7623-audsys",
> 		
> 		
>      "mediatek,mt2701-audsys",
> 		
> 		
>      "syscon";
> 		
> 	...
> 		
> };
> 	};
> 
> And if audsys only exposes clocks, you don't even need a subnode to represent 
> it, the audio controller itself can be a clock provider.
> 
> 	afe: audio-controller@11220000 {
> 		
> compatible = "mediatek,mt7623-audio",
> 		
> 	     "mediatek,mt2701-audio";
> 		
> #clock-cells = <1>;
> 		
> ..
> 	};
> 
> > > 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;
> 
>