linux-kernel - Re: [PATCH v10 1/6] drm/bridge: cadence: cdns-mhdp8546-core: Set the mhdp connector earlier in atomic

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Message-ID: <486581cb-6f67-4e7b-a58f-c0f96d2babd9@ideasonboard.com>
Date: Mon, 22 Dec 2025 14:54:53 +0200
From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To: Harikrishna Shenoy <h-shenoy@...com>
Cc: Laurent.pinchart@...asonboard.com, airlied@...il.com,
 andrzej.hajda@...el.com, andy.yan@...k-chips.com, aradhya.bhatia@...ux.dev,
 devarsht@...com, dianders@...omium.org, dri-devel@...ts.freedesktop.org,
 javierm@...hat.com, jernej.skrabec@...il.com, jonas@...boo.se,
 linux-kernel@...r.kernel.org, linux@...blig.org, luca.ceresoli@...tlin.com,
 lumag@...nel.org, lyude@...hat.com, maarten.lankhorst@...ux.intel.com,
 mordan@...ras.ru, mripard@...nel.org, neil.armstrong@...aro.org,
 rfoss@...nel.org, s-jain1@...com, simona@...ll.ch, tzimmermann@...e.de,
 u-kumar1@...com
Subject: Re: [PATCH v10 1/6] drm/bridge: cadence: cdns-mhdp8546-core: Set the
 mhdp connector earlier in atomic_enable()

Hi,

On 09/12/2025 14:03, Harikrishna Shenoy wrote:
> From: Jayesh Choudhary <j-choudhary@...com>
> 
> In case if we get errors in cdns_mhdp_link_up() or cdns_mhdp_reg_read()
> in atomic_enable, we will go to cdns_mhdp_modeset_retry_fn() and will hit
> NULL pointer while trying to access the mutex. We need the connector to
> be set before that. Unlike in legacy cases with flag
> !DRM_BRIDGE_ATTACH_NO_CONNECTOR, we do not have connector initialised
> in bridge_attach(), so add the mhdp->connector_ptr in device structure
> to handle both cases with DRM_BRIDGE_ATTACH_NO_CONNECTOR and
> !DRM_BRIDGE_ATTACH_NO_CONNECTOR, set it in atomic_enable() earlier to
> avoid possible NULL pointer dereference in recovery paths like
> modeset_retry_fn() with the DRM_BRIDGE_ATTACH_NO_CONNECTOR flag set.
> 
> Fixes: c932ced6b585 ("drm/tidss: Update encoder/bridge chain connect model")
> Signed-off-by: Jayesh Choudhary <j-choudhary@...com>
> Signed-off-by: Harikrishna Shenoy <h-shenoy@...com>
> ---
>  .../drm/bridge/cadence/cdns-mhdp8546-core.c   | 29 ++++++++++---------
>  .../drm/bridge/cadence/cdns-mhdp8546-core.h   |  1 +
>  .../drm/bridge/cadence/cdns-mhdp8546-hdcp.c   | 18 +++++++++---
>  3 files changed, 30 insertions(+), 18 deletions(-)
Reviewed-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>

 Tomi