linux-kernel - Re: [PATCH v3 09/15] drm/bridge: analogix_dp: Add support to get panel from the DP AUX bus

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Message-ID: <irh3rei7to7gevrr5dqwa3qr3nl2lunenyvvvlqnpiyplbk2vj@ooedydnvl4df>
Date: Fri, 20 Dec 2024 02:17:50 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Damon Ding <damon.ding@...k-chips.com>
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 09/15] drm/bridge: analogix_dp: Add support to get
 panel from the DP AUX bus

On Thu, Dec 19, 2024 at 04:05:58PM +0800, Damon Ding wrote:
> If the panel can not be found in the beginning of rockchip_dp_probe()
> using the platform bus, we can still try to find it in analogix_dp_bind()
> through the DP AUX bus after the &analogix_dp_device.aux has been
> initialized.
> 
> Signed-off-by: Damon Ding <damon.ding@...k-chips.com>
> ---
>  .../drm/bridge/analogix/analogix_dp_core.c    | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> index 9429c50cc1bc..eae02819e3bb 100644
> --- a/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> +++ b/drivers/gpu/drm/bridge/analogix/analogix_dp_core.c
> @@ -19,12 +19,14 @@
>  #include <linux/platform_device.h>
>  
>  #include <drm/bridge/analogix_dp.h>
> +#include <drm/display/drm_dp_aux_bus.h>
>  #include <drm/drm_atomic.h>
>  #include <drm/drm_atomic_helper.h>
>  #include <drm/drm_bridge.h>
>  #include <drm/drm_crtc.h>
>  #include <drm/drm_device.h>
>  #include <drm/drm_edid.h>
> +#include <drm/drm_of.h>
>  #include <drm/drm_panel.h>
>  #include <drm/drm_print.h>
>  #include <drm/drm_probe_helper.h>
> @@ -1733,6 +1735,23 @@ int analogix_dp_bind(struct analogix_dp_device *dp, struct drm_device *drm_dev)
>  		goto err_disable_pm_runtime;
>  	}
>  
> +	if (!dp->plat_data->panel) {
> +		/*
> +		 * If the edp-panel module has not yet been initialized, the
> +		 * devm_of_dp_aux_populate_bus() function will return 0 and
> +		 * the done_probing() callback will not be called either.
> +		 * Consequently, the panel will never be found.
> +		 *
> +		 * This is the reason why we do not use the done_probing()
> +		 * callback and do not check the reture value here.

NAK. It is there for exactly this reason, to account for the panel
driver being not present yet. Please make a use of the done_probing()
callback.

> +		 */
> +		devm_of_dp_aux_populate_bus(&dp->aux, NULL);
> +		ret = drm_of_find_panel_or_bridge(dp->dev->of_node, 1, 0,
> +						  &dp->plat_data->panel, NULL);
> +		if (ret)
> +			goto err_unregister_aux;
> +	}
> +
>  	ret = analogix_dp_create_bridge(drm_dev, dp);
>  	if (ret) {
>  		DRM_ERROR("failed to create bridge (%d)\n", ret);
> -- 
> 2.34.1
> 

-- 
With best wishes
Dmitry