Re: [PATCH v3 02/13] drm: bridge: dw_hdmi: Only notify connected status on HPD interrupt

From: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
To: Andrzej Hajda <andrzej.hajda@intel.com>,
	Neil Armstrong <neil.armstrong@linaro.org>,
	Robert Foss <rfoss@kernel.org>,
	Laurent Pinchart <Laurent.pinchart@ideasonboard.com>,
	Jonas Karlman <jonas@kwiboo.se>,
	Jernej Skrabec <jernej.skrabec@gmail.com>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Maxime Ripard <mripard@kernel.org>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	David Airlie <airlied@gmail.com>, Simona Vetter <simona@ffwll.ch>,
	Lucas Stach <l.stach@pengutronix.de>,
	dri-devel@lists.freedesktop.org
Cc: Christian Hewitt <christianshewitt@gmail.com>,
	Diederik de Haas <diederik@cknow-tech.com>,
	dri-devel@lists.freedesktop.org,
	linux-rockchip@lists.infradead.org, linux-kernel@vger.kernel.org,
	Jonas Karlman <jonas@kwiboo.se>
Subject: Re: [PATCH v3 02/13] drm: bridge: dw_hdmi: Only notify connected status on HPD interrupt
Date: Mon, 27 Apr 2026 20:04:10 +0200	[thread overview]
Message-ID: <5ozaSaKzQeSilqZavTuKOw@collabora.com> (raw)
In-Reply-To: <20260403185303.80748-3-jonas@kwiboo.se>

On Friday, 3 April 2026 20:52:48 Central European Summer Time Jonas Karlman wrote:
> drm_helper_hpd_irq_event() and drm_bridge_hpd_notify() may incorrectly
> be called with a connected status when HPD is high and RX sense is
> changed. This typically happens when the HDMI cable is unplugged,
> shortly before the HPD is changed to low.
> 
> The original intent of commit da09daf88108 ("drm: bridge: dw_hdmi: only
> trigger hotplug event on link change") was to signal hotplug event at
> correct interrupt states.
> 
> Based on the commit message the intent was to trigger hotplug event:
> - when HPD goes high (plugin)
> - when both HPD and RX sense has gone low (plugout)
> 
> However, following interrupt state changes can typically be observed
> when the HDMI cable is unplugged:
> - RX interrupt:  HPD=high RX=low  -> triggers a connected event
> - HPD interrupt: HPD=low  RX=low  -> triggers a disconnected event
> 
> Fix this by only notify connected status on the HPD interrupt when HPD
> is going high, not on the RX sense interrupt when RX sense is changed.
> 
> After this a connected event should be triggered when HPD=high at HPD
> interrupt, and a disconnected event should be triggered when both
> HPD=low and RX=low at either HPD or RX interrupt.
> 
> Fixes: da09daf88108 ("drm: bridge: dw_hdmi: only trigger hotplug event on link change")
> Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
> ---
> v3: Update commit message
> v2: New patch
> ---
>  drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> index 9febcb58a1df..3b851f12adfe 100644
> --- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> +++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
> @@ -3140,7 +3140,8 @@ static irqreturn_t dw_hdmi_irq(int irq, void *dev_id)
>  			mutex_unlock(&hdmi->cec_notifier_mutex);
>  		}
>  
> -		if (phy_stat & HDMI_PHY_HPD)
> +		if ((intr_stat & HDMI_IH_PHY_STAT0_HPD) &&
> +		    (phy_stat & HDMI_PHY_HPD))
>  			status = connector_status_connected;
>  
>  		if (!(phy_stat & (HDMI_PHY_HPD | HDMI_PHY_RX_SENSE)))
> 

Reviewed-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>


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