linux-kernel - Re: [PATCH v3 08/15] drm/rockchip: analogix_dp: Add support to get panel from the DP AUX bus

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Message-ID: <3663bbec-fcb2-4f93-aae6-3c2082491069@rock-chips.com>
Date: Fri, 20 Dec 2024 16:29:27 +0800
From: Damon Ding <damon.ding@...k-chips.com>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: heiko@...ech.de, robh@...nel.org, krzk+dt@...nel.org,
 conor+dt@...nel.org, rfoss@...nel.org, vkoul@...nel.org,
 sebastian.reichel@...labora.com, cristian.ciocaltea@...labora.com,
 l.stach@...gutronix.de, andy.yan@...k-chips.com, hjc@...k-chips.com,
 algea.cao@...k-chips.com, kever.yang@...k-chips.com,
 dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org, linux-rockchip@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-phy@...ts.infradead.org
Subject: Re: [PATCH v3 08/15] drm/rockchip: analogix_dp: Add support to get
 panel from the DP AUX bus

Hi Dmitry,

On 2024/12/20 8:16, Dmitry Baryshkov wrote:
> On Thu, Dec 19, 2024 at 04:05:57PM +0800, Damon Ding wrote:
>> The rockchip_dp_of_panel_on_aux_bus() helps to check whether the DT
>> configurations related to the DP AUX bus are correct or not.
>>
>> If failed to get the panel from the platform bus, it is good to try
>> the DP AUX bus. Then, the probing process will continue until it enters
>> the analogix_dp_bind(), where devm_of_dp_aux_populate_bus() is called
>> after &analogix_dp_device.aux has been initialized.
> 
> No. devm_of_dp_aux_populate_bus() should be called before bind(). And
> bind should only be called from the done_probing() callback. The reason
> is very simple: the panel driver might be built as a module and might be
> not available when the analogix driver is being probed.
> 
> Also, please invert the logic of the commit message (and the driver).
> The platform bus should be a fallback if there is no AUX bus panel, not
> other way around.
> 

I have tried the logic as you recommanded, and it is really a good way. 
I will fix this in the next version.

>>
>> Signed-off-by: Damon Ding <damon.ding@...k-chips.com>
>> ---
>>   .../gpu/drm/rockchip/analogix_dp-rockchip.c   | 24 +++++++++++++++++--
>>   1 file changed, 22 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/rockchip/analogix_dp-rockchip.c b/drivers/gpu/drm/rockchip/analogix_dp-rockchip.c
>> index ba5263f85ee2..60c902abf40b 100644
>> --- a/drivers/gpu/drm/rockchip/analogix_dp-rockchip.c
>> +++ b/drivers/gpu/drm/rockchip/analogix_dp-rockchip.c
>> @@ -317,6 +317,24 @@ static const struct drm_encoder_helper_funcs rockchip_dp_encoder_helper_funcs =
>>   	.atomic_check = rockchip_dp_drm_encoder_atomic_check,
>>   };
>>   
>> +static bool rockchip_dp_of_panel_on_aux_bus(const struct device_node *np)
>> +{
>> +	struct device_node *bus_node, *panel_node;
>> +
>> +	bus_node = of_get_child_by_name(np, "aux-bus");
>> +	if (!bus_node)
>> +		return false;
>> +
>> +	panel_node = of_get_child_by_name(bus_node, "panel");
>> +	of_node_put(bus_node);
>> +	if (!panel_node)
>> +		return false;
>> +
>> +	of_node_put(panel_node);
>> +
>> +	return true;
>> +}
>> +
>>   static int rockchip_dp_of_probe(struct rockchip_dp_device *dp)
>>   {
>>   	struct device *dev = dp->dev;
>> @@ -435,8 +453,10 @@ static int rockchip_dp_probe(struct platform_device *pdev)
>>   		return -ENODEV;
>>   
>>   	ret = drm_of_find_panel_or_bridge(dev->of_node, 1, 0, &panel, NULL);
>> -	if (ret < 0)
>> -		return ret;
>> +	if (ret < 0) {
>> +		if (!rockchip_dp_of_panel_on_aux_bus(dev->of_node))
>> +			return ret;
>> +	}
>>   
>>   	dp = devm_kzalloc(dev, sizeof(*dp), GFP_KERNEL);
>>   	if (!dp)
>> -- 
>> 2.34.1
>>
> 

Best regards,
Damon