linux-kernel - Re: [PATCH v4 07/15] drm/bridge: Add helper to reset bridge pipeline

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <sqsk3ievl3kujkljqosww233yio4uke5met7zqhzssmehzdck5@doaikab7bggr>
Date: Wed, 26 Feb 2025 08:41:54 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Maxime Ripard <mripard@...nel.org>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, 
	Simona Vetter <simona@...ll.ch>, Andrzej Hajda <andrzej.hajda@...el.com>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>, Jonas Karlman <jonas@...boo.se>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, Douglas Anderson <dianders@...omium.org>, 
	Herve Codina <herve.codina@...tlin.com>, dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
	Simona Vetter <simona.vetter@...ll.ch>
Subject: Re: [PATCH v4 07/15] drm/bridge: Add helper to reset bridge pipeline

On Tue, Feb 25, 2025 at 05:43:55PM +0100, Maxime Ripard wrote:
> Let's provide an helper to make it easier for bridge drivers to
> power-cycle their bridge.
> 
> Co-developed-by: Simona Vetter <simona.vetter@...ll.ch>
> Signed-off-by: Maxime Ripard <mripard@...nel.org>
> ---
>  drivers/gpu/drm/drm_bridge.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
>  include/drm/drm_bridge.h     |  2 ++
>  2 files changed, 46 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> index 8241c00e4506eceeb9bb4ba74a38d8f360c65d38..ca894531a2042fc9296c40a1f51a6cdea6e97ed7 100644
> --- a/drivers/gpu/drm/drm_bridge.c
> +++ b/drivers/gpu/drm/drm_bridge.c
> @@ -24,10 +24,11 @@
>  #include <linux/err.h>
>  #include <linux/media-bus-format.h>
>  #include <linux/module.h>
>  #include <linux/mutex.h>
>  
> +#include <drm/drm_atomic_helper.h>
>  #include <drm/drm_atomic_state_helper.h>
>  #include <drm/drm_bridge.h>
>  #include <drm/drm_debugfs.h>
>  #include <drm/drm_edid.h>
>  #include <drm/drm_encoder.h>
> @@ -1269,10 +1270,53 @@ void drm_bridge_hpd_notify(struct drm_bridge *bridge,
>  		bridge->hpd_cb(bridge->hpd_data, status);
>  	mutex_unlock(&bridge->hpd_mutex);
>  }
>  EXPORT_SYMBOL_GPL(drm_bridge_hpd_notify);
>  
> +/**
> + * drm_bridge_reset_crtc - Reset the pipeline feeding a bridge
> + * @bridge: DRM bridge to reset
> + * @ctx: lock acquisition context
> + *
> + * Reset a @bridge pipeline. It will power-cycle all active components
> + * between the CRTC and connector that bridge is connected to.
> + *
> + * Returns:
> + *
> + * 0 on success or a negative error code on failure. If the error
> + * returned is EDEADLK, the whole atomic sequence must be restarted.
> + */
> +int drm_bridge_reset_crtc(struct drm_bridge *bridge,
> +			  struct drm_modeset_acquire_ctx *ctx)
> +{
> +	struct drm_connector *connector;
> +	struct drm_encoder *encoder = bridge->encoder;
> +	struct drm_device *dev = encoder->dev;
> +	struct drm_crtc *crtc;
> +	int ret;
> +
> +	ret = drm_modeset_lock(&dev->mode_config.connection_mutex, ctx);
> +	if (ret)
> +		return ret;
> +
> +	connector = drm_atomic_get_connector_for_encoder(encoder, ctx);
> +	if (IS_ERR(connector)) {
> +		ret = PTR_ERR(connector);
> +		goto out;
> +	}
> +

Should there be a check for connector->state before accessing
connector->state->crtc ?

> +	crtc = connector->state->crtc;
> +	ret = drm_atomic_helper_reset_crtc(crtc, ctx);
> +	if (ret)
> +		goto out;
> +
> +out:
> +	drm_modeset_unlock(&dev->mode_config.connection_mutex);
> +	return ret;
> +}
> +EXPORT_SYMBOL(drm_bridge_reset_crtc);
> +
>  #ifdef CONFIG_OF
>  /**
>   * of_drm_find_bridge - find the bridge corresponding to the device node in
>   *			the global bridge list
>   *
> diff --git a/include/drm/drm_bridge.h b/include/drm/drm_bridge.h
> index 6fb1da7c195e99143a67a999d16fe361c1e3f4ab..32169e62463bb268a281a5903c0c9f448a1042b3 100644
> --- a/include/drm/drm_bridge.h
> +++ b/include/drm/drm_bridge.h
> @@ -1085,10 +1085,12 @@ void drm_bridge_hpd_enable(struct drm_bridge *bridge,
>  				      enum drm_connector_status status),
>  			   void *data);
>  void drm_bridge_hpd_disable(struct drm_bridge *bridge);
>  void drm_bridge_hpd_notify(struct drm_bridge *bridge,
>  			   enum drm_connector_status status);
> +int drm_bridge_reset_crtc(struct drm_bridge *bridge,
> +			  struct drm_modeset_acquire_ctx *ctx);
>  
>  #ifdef CONFIG_DRM_PANEL_BRIDGE
>  bool drm_bridge_is_panel(const struct drm_bridge *bridge);
>  struct drm_bridge *drm_panel_bridge_add(struct drm_panel *panel);
>  struct drm_bridge *drm_panel_bridge_add_typed(struct drm_panel *panel,
> 
> -- 
> 2.48.1
> 

-- 
With best wishes
Dmitry