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: <73bpf77trhqdo5amfxbn4qhlwf4ta7hmouwfen7m3aslycd3bj@72artzwafbmq>
Date: Tue, 30 Sep 2025 23:17:57 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Damon Ding <damon.ding@...k-chips.com>
Cc: andrzej.hajda@...el.com, neil.armstrong@...aro.org, rfoss@...nel.org,
        Laurent.pinchart@...asonboard.com, jonas@...boo.se,
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Subject: Re: [PATCH v6 07/18] drm/exynos: exynos_dp: Apply legacy bridge to
 parse the display-timings node

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.

> +
>  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.

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

-- 
With best wishes
Dmitry