Re: [PATCH v3 1/3] drm/exynos: dp: add of_graph dt binding support for panel

[Inki Dae <inki.dae@samsung.com>]

Hi Javier,

2015년 12월 03일 22:55에 Javier Martinez Canillas 이(가) 쓴 글:
> Hello Inki,
> 
> I found that v2 of this patch is alredy in your exynos-drm for-next branch so
> so I had to revert it in linux-next to apply this one to test. You shouldn't
> push patches that were still not reviewed (specially the ones that weren't
> tested like this one) to your branch that gets pulled by -next. The idea of
> -next is to have some test coverage but it should be as stable as possible.

exynos-drm/for-next branch is not really for-next branch. This branch is used
only for integration test. As you know, there are many exynos maintainers
and they have their own repository. So we would need to test the integration.
For this, exynos-drm/for-next is merged to linux-next not Dave's tree.
Only exynos-drm-next branch will be merged to Dave's tree so only reviewed and
tested patches will be merged to exynos-drm-next.

> 
> On 12/03/2015 06:30 AM, Inki Dae wrote:
>> This patch adds of_graph dt binding support for panel device
>> and also keeps the backward compatibility.
>>
>> i.e.,
>> The dts file for Exynos5800 based peach pi board
>> has a panel property so we need to keep the backward compatibility.
>>
>> Changelog v3:
>> - bind only one of two nodes outbound - panel or bridge.
>>
> 
> This patch fixes one of the comments I had for v2 but I've another
> comment below.
>  
>> Changelog v2:
>> - return -EINVAL if getting a port node failed.
>>
>> Signed-off-by: Inki Dae <inki.dae@samsung.com>
>> ---
>>  drivers/gpu/drm/exynos/exynos_dp_core.c | 21 ++++++++++++++++++++-
>>  1 file changed, 20 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/exynos/exynos_dp_core.c b/drivers/gpu/drm/exynos/exynos_dp_core.c
>> index 94f02a0..60260a0 100644
>> --- a/drivers/gpu/drm/exynos/exynos_dp_core.c
>> +++ b/drivers/gpu/drm/exynos/exynos_dp_core.c
>> @@ -1392,7 +1392,7 @@ static const struct component_ops exynos_dp_ops = {
>>  static int exynos_dp_probe(struct platform_device *pdev)
>>  {
>>  	struct device *dev = &pdev->dev;
>> -	struct device_node *panel_node, *bridge_node, *endpoint;
>> +	struct device_node *panel_node = NULL, *bridge_node, *endpoint = NULL;
>>  	struct exynos_dp_device *dp;
>>  	int ret;
>>  
>> @@ -1403,14 +1403,32 @@ static int exynos_dp_probe(struct platform_device *pdev)
>>  
>>  	platform_set_drvdata(pdev, dp);
>>  
>> +	/* This is for the backward compatibility. */
>>  	panel_node = of_parse_phandle(dev->of_node, "panel", 0);
>>  	if (panel_node) {
>>  		dp->panel = of_drm_find_panel(panel_node);
>>  		of_node_put(panel_node);
>>  		if (!dp->panel)
>>  			return -EPROBE_DEFER;
>> +	} else {
>> +		endpoint = of_graph_get_next_endpoint(dev->of_node, NULL);
>> +		if (endpoint) {
>> +			panel_node = of_graph_get_remote_port_parent(endpoint);
> 
> Here is asssumed that the endpoint will be a panel but it could be that there
> is no "panel" phandle but the port is for a bridge chip (i.e: Peach Pit) so
> this assumption seems fragile to me.
> 
> That's what I meant when I said "Assuming you can make a distinction if the
> endpoint is a panel or a bridge" in the other thread.
> 
>> +			if (panel_node) {
>> +				dp->panel = of_drm_find_panel(panel_node);
>> +				of_node_put(panel_node);
>> +				if (!dp->panel)
>> +					return -EPROBE_DEFER;
>> +			} else {
>> +				DRM_ERROR("no port node for panel device.\n");
>> +				return -EINVAL;
>> +			}
>> +		}
>>  	}
>>  
>> +	if (endpoint)
>> +		goto out;
>> +
> 
> Ok, so IIUC what's done here is to test if the panel lookup failed, then the
> endpoint is looked up again but this time a call to of_drm_find_bridge() is
> made instead of a call to of_drm_find_panel(). I wonder if there is a better
> way to do this...
> 
> In any case then I think you should test if (panel_node) instead of endpoint.
> 
>>  	endpoint = of_graph_get_next_endpoint(dev->of_node, NULL);
>>  	if (endpoint) {
>>  		bridge_node = of_graph_get_remote_port_parent(endpoint);
>> @@ -1423,6 +1441,7 @@ static int exynos_dp_probe(struct platform_device *pdev)
>>  			return -EPROBE_DEFER;
>>  	}
>>  
>> +out:
>>  	pm_runtime_enable(dev);
>>  
>>  	ret = component_add(&pdev->dev, &exynos_dp_ops);
>>
> 
> I can't think of a better way to lookup either a panel or a bridge though
> and I'm not that familiar with DRM so with the correct check, the patch
> looks good to me.
> 
> Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
> 
> Also on an Exynos5800 Peach Pi with the DTS patch I shared, the display
> is working correctly and also I tested without the DTS patch to make
> sure that it does not cause a regression for older DTBs.
> 
> Tested-by: Javier Martinez Canillas <javier@osg.samsung.com>

Thanks,
Inki Dae

> 
> Best regards,
>