linux-kernel - Re: [PATCH v6 07/18] drm/exynos: exynos_dp: Apply legacy bridge to parse the display-timings node

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Message-ID: <d4353b1e-53e5-4a5f-8da0-df3493d95ec3@rock-chips.com>
Date: Thu, 9 Oct 2025 10:01:39 +0800
From: Damon Ding <damon.ding@...k-chips.com>
To: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
Cc: andrzej.hajda@...el.com, neil.armstrong@...aro.org, rfoss@...nel.org,
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Subject: Re: [PATCH v6 07/18] drm/exynos: exynos_dp: Apply legacy bridge to
 parse the display-timings node

Hi Dmitry,

On 10/1/2025 4:17 AM, Dmitry Baryshkov wrote:
> On Tue, Sep 30, 2025 at 05:09:09PM +0800, Damon Ding wrote:
>> If there is neither a panel nor a bridge, the display timing can be
>> parsed from the display-timings node under the dp node.
>>
>> In order to get rid of &analogix_dp_plat_data.get_modes() and make
>> the codes more consistent, apply DRM legacy bridge to parse display
>> timings.
>>
>> Signed-off-by: Damon Ding <damon.ding@...k-chips.com>
>>
>> ------
>>
>> Changes in v6:
>> - Apply DRM legacy bridge to parse display timings intead of
>>    implementing the same codes only for Exynos DP.
>> ---
>>   drivers/gpu/drm/exynos/Kconfig     |  1 +
>>   drivers/gpu/drm/exynos/exynos_dp.c | 71 +++++++++---------------------
>>   2 files changed, 22 insertions(+), 50 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/exynos/Kconfig b/drivers/gpu/drm/exynos/Kconfig
>> index 0d13828e7d9e..66665d317848 100644
>> --- a/drivers/gpu/drm/exynos/Kconfig
>> +++ b/drivers/gpu/drm/exynos/Kconfig
>> @@ -72,6 +72,7 @@ config DRM_EXYNOS_DP
>>   	select DRM_ANALOGIX_DP
>>   	select DRM_DISPLAY_DP_HELPER
>>   	default DRM_EXYNOS
>> +	select DRM_LEGACY_BRIDGE
>>   	select DRM_PANEL
>>   	help
>>   	  This enables support for DP device.
>> diff --git a/drivers/gpu/drm/exynos/exynos_dp.c b/drivers/gpu/drm/exynos/exynos_dp.c
>> index e20513164032..507d0a98fe5b 100644
>> --- a/drivers/gpu/drm/exynos/exynos_dp.c
>> +++ b/drivers/gpu/drm/exynos/exynos_dp.c
>> @@ -19,6 +19,7 @@
>>   #include <video/videomode.h>
>>   
>>   #include <drm/bridge/analogix_dp.h>
>> +#include <drm/bridge/legacy-bridge.h>
>>   #include <drm/drm_atomic_helper.h>
>>   #include <drm/drm_bridge.h>
>>   #include <drm/drm_crtc.h>
>> @@ -38,11 +39,23 @@ struct exynos_dp_device {
>>   	struct drm_device          *drm_dev;
>>   	struct device              *dev;
>>   
>> -	struct videomode           vm;
>>   	struct analogix_dp_device *adp;
>>   	struct analogix_dp_plat_data plat_data;
>>   };
>>   
>> +static int exynos_dp_legacy_bridge_init(struct exynos_dp_device *dp,
>> +					struct drm_bridge **bridge)
>> +{
>> +	if (!bridge)
>> +		return -EINVAL;
> 
> Well, this can't happen, can it?
> 
>> +
>> +	*bridge = devm_drm_legacy_bridge(dp->dev, dp->dev->of_node, DRM_MODE_CONNECTOR_eDP);
>> +	if (IS_ERR(*bridge))
>> +		return PTR_ERR(*bridge);
>> +
>> +	return 0;
>> +}
> 
> I'd suggest inlining the function. It doesn't make sense to have
> one-line wrapper.
> 

Will do in v7.

>> +
>>   static int exynos_dp_crtc_clock_enable(struct analogix_dp_plat_data *plat_data,
>>   				bool enable)
>>   {
> 
> [...]
> 
>>   static int exynos_dp_bridge_attach(struct analogix_dp_plat_data *plat_data,
>>   				   struct drm_bridge *bridge,
>>   				   struct drm_connector *connector)
>>   {
>>   	struct exynos_dp_device *dp = to_dp(plat_data);
>> +	enum drm_bridge_attach_flags flags = 0;
>>   	int ret;
>>   
>>   	/* Pre-empt DP connector creation if there's a bridge */
>>   	if (plat_data->next_bridge) {
>> -		ret = drm_bridge_attach(&dp->encoder, plat_data->next_bridge, bridge,
>> -					0);
>> +		if (drm_bridge_is_legacy(plat_data->next_bridge))
> 
> I see... You are going to kill this line in one of the next patches, but
> the API will stay. I suggest adding a flag to the exynos_dp_device and
> then removing the flag once you migrate to drm_bridge_connector.
> 

Yes, using a temporary flag is a better approach.

>> +			flags = DRM_BRIDGE_ATTACH_NO_CONNECTOR;
>> +
>> +		ret = drm_bridge_attach(&dp->encoder, plat_data->next_bridge, bridge, flags);
>>   		if (ret)
>>   			return ret;
>>   	}
> 

Best regards,
Damon