linux-kernel - Re: [PATCH v3 01/12] drm/bridge: Fix the stop condition of drm_bridge_chain_pre

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Message-ID: <YGpeo9LV4uAh1B7u@pendragon.ideasonboard.com>
Date:   Mon, 5 Apr 2021 03:49:39 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Douglas Anderson <dianders@...omium.org>
Cc:     Andrzej Hajda <a.hajda@...sung.com>,
        Neil Armstrong <narmstrong@...libre.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...l.net>,
        Sam Ravnborg <sam@...nborg.org>,
        Linus W <linus.walleij@...aro.org>,
        Bjorn Andersson <bjorn.andersson@...aro.org>,
        robdclark@...omium.org, Stephen Boyd <swboyd@...omium.org>,
        Steev Klimaszewski <steev@...i.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        linux-arm-msm@...r.kernel.org,
        Stanislav Lisovskiy <stanislav.lisovskiy@...el.com>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Daniel Vetter <daniel@...ll.ch>,
        David Airlie <airlied@...ux.ie>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 01/12] drm/bridge: Fix the stop condition of
 drm_bridge_chain_pre_enable()

Hi Doug,

Thank you for the patch.

On Fri, Apr 02, 2021 at 03:28:35PM -0700, Douglas Anderson wrote:
> The drm_bridge_chain_pre_enable() is not the proper opposite of
> drm_bridge_chain_post_disable(). It continues along the chain to
> _before_ the starting bridge. Let's fix that.
> 
> Fixes: 05193dc38197 ("drm/bridge: Make the bridge chain a double-linked list")
> Signed-off-by: Douglas Anderson <dianders@...omium.org>
> Reviewed-by: Andrzej Hajda <a.hajda@...sung.com>
> ---
> 
> (no changes since v1)
> 
>  drivers/gpu/drm/drm_bridge.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> index 64f0effb52ac..044acd07c153 100644
> --- a/drivers/gpu/drm/drm_bridge.c
> +++ b/drivers/gpu/drm/drm_bridge.c
> @@ -522,6 +522,9 @@ void drm_bridge_chain_pre_enable(struct drm_bridge *bridge)
>  	list_for_each_entry_reverse(iter, &encoder->bridge_chain, chain_node) {
>  		if (iter->funcs->pre_enable)
>  			iter->funcs->pre_enable(iter);
> +
> +		if (iter == bridge)
> +			break;

This looks good as it matches drm_atomic_bridge_chain_disable().

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

I'm curious though, given that the bridge passed to the function should
be the one closest to the encoder, does this make a difference ?

>  	}
>  }
>  EXPORT_SYMBOL(drm_bridge_chain_pre_enable);

-- 
Regards,

Laurent Pinchart