linux-kernel - Re: [PATCH 3/5] drm/bridge: simple-bridge: Allow acquiring the next bridge with fwnode API

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Message-ID: <7f5e1c37-a637-494a-ab52-cad83095f2a6@linux.dev>
Date: Tue, 23 Jan 2024 20:18:22 +0800
From: Sui Jingfeng <sui.jingfeng@...ux.dev>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc: David Airlie <airlied@...il.com>,
 Neil Armstrong <neil.armstrong@...aro.org>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 Daniel Vetter <daniel@...ll.ch>, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/5] drm/bridge: simple-bridge: Allow acquiring the next
 bridge with fwnode API

Hi,


On 2024/1/23 09:18, Laurent Pinchart wrote:
> On Tue, Jan 23, 2024 at 12:32:18AM +0800, Sui Jingfeng wrote:
>> Which make it possible to use this driver on non-DT based systems,
>> meanwhile, made no functional changes for DT based systems.
>>
>> Signed-off-by: Sui Jingfeng <sui.jingfeng@...ux.dev>
>> ---
>>   drivers/gpu/drm/bridge/simple-bridge.c | 51 ++++++++++++++++++++++----
>>   1 file changed, 44 insertions(+), 7 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/bridge/simple-bridge.c b/drivers/gpu/drm/bridge/simple-bridge.c
>> index 595f672745b9..cfea5a67cc5b 100644
>> --- a/drivers/gpu/drm/bridge/simple-bridge.c
>> +++ b/drivers/gpu/drm/bridge/simple-bridge.c
>> @@ -184,6 +184,39 @@ static const void *simple_bridge_get_match_data(const struct device *dev)
>>   	return NULL;
>>   }
>>   
>> +static int simple_bridge_get_next_bridge_by_fwnode(struct device *dev,
>> +						   struct drm_bridge **next_bridge)
>> +{
>> +	struct drm_bridge *bridge;
>> +	struct fwnode_handle *ep;
>> +	struct fwnode_handle *remote;
>> +
>> +	ep = fwnode_graph_get_endpoint_by_id(dev->fwnode, 1, 0, 0);
>> +	if (!ep) {
>> +		dev_err(dev, "The endpoint is unconnected\n");
>> +		return -EINVAL;
>> +	}
>> +
>> +	remote = fwnode_graph_get_remote_port_parent(ep);
>> +	fwnode_handle_put(ep);
>> +	if (!remote) {
>> +		dev_err(dev, "No valid remote node\n");
>> +		return -ENODEV;
>> +	}
>> +
>> +	bridge = drm_bridge_find_by_fwnode(remote);
>> +	fwnode_handle_put(remote);
>> +
>> +	if (!bridge) {
>> +		dev_warn(dev, "Next bridge not found, deferring probe\n");
>> +		return -EPROBE_DEFER;
>> +	}
>> +
>> +	*next_bridge = bridge;
>> +
>> +	return 0;
>> +}
>> +
> Hmmmm yes, this convinces me further that we should switch to fwnode,
> not implement fwnode and OF side-by-side.
>

OK, I'm agree with you.


But this means that I have to make the drm_bridge_find_by_fwnode() function works
on both DT systems and non-DT systems. This is also means that we will no longer
need to call of_drm_find_bridge() function anymore. This will eventually lead to
completely remove of_drm_find_bridge()?


As far as I can see, if I follow you suggestion, drm/bridge subsystem will
encountering a *big* refactor. My 'side-by-side' approach allows co-exist.
It is not really meant to purge OF. I feel it is a little bit of aggressive.

hello Maxime, are you watching this? what do you think?


>>   static int simple_bridge_probe(struct platform_device *pdev)
>>   {
>>   	struct simple_bridge *sbridge;
>> @@ -199,14 +232,17 @@ static int simple_bridge_probe(struct platform_device *pdev)
>>   	else
>>   		sbridge->info = simple_bridge_get_match_data(&pdev->dev);
>>   
>> -	/* Get the next bridge in the pipeline. */
>> -	remote = of_graph_get_remote_node(pdev->dev.of_node, 1, -1);
>> -	if (!remote)
>> -		return -EINVAL;
>> -
>> -	sbridge->next_bridge = of_drm_find_bridge(remote);
>> -	of_node_put(remote);
>> +	if (pdev->dev.of_node) {
>> +		/* Get the next bridge in the pipeline. */
>> +		remote = of_graph_get_remote_node(pdev->dev.of_node, 1, -1);
>> +		if (!remote)
>> +			return -EINVAL;
>>   
>> +		sbridge->next_bridge = of_drm_find_bridge(remote);
>> +		of_node_put(remote);
>> +	} else {
>> +		simple_bridge_get_next_bridge_by_fwnode(&pdev->dev, &sbridge->next_bridge);
>> +	}
>>   	if (!sbridge->next_bridge) {
>>   		dev_dbg(&pdev->dev, "Next bridge not found, deferring probe\n");
>>   		return -EPROBE_DEFER;
>> @@ -231,6 +267,7 @@ static int simple_bridge_probe(struct platform_device *pdev)
>>   	/* Register the bridge. */
>>   	sbridge->bridge.funcs = &simple_bridge_bridge_funcs;
>>   	sbridge->bridge.of_node = pdev->dev.of_node;
>> +	sbridge->bridge.fwnode = pdev->dev.fwnode;
>>   	sbridge->bridge.timings = sbridge->info->timings;
>>   
>>   	drm_bridge_add(&sbridge->bridge);
>> -- 
>> 2.25.1
>>