linux-kernel - [PATCH 5.15 450/530] drm: bridge: dw_hdmi: only trigger hotplug event on link change

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Message-Id: <20221024113105.419943323@linuxfoundation.org>
Date:   Mon, 24 Oct 2022 13:33:14 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Lucas Stach <l.stach@...gutronix.de>,
        Robert Foss <robert.foss@...aro.org>,
        Sasha Levin <sashal@...nel.org>,
        Neil Armstrong <narmstrong@...libre.com>
Subject: [PATCH 5.15 450/530] drm: bridge: dw_hdmi: only trigger hotplug event on link change

From: Lucas Stach <l.stach@...gutronix.de>

[ Upstream commit da09daf881082266e4075657fac53c7966de8e4d ]

There are two events that signal a real change of the link state: HPD going
high means the sink is newly connected or wants the source to re-read the
EDID, RX sense going low is a indication that the link has been disconnected.

Ignore the other two events that also trigger interrupts, but don't need
immediate attention: HPD going low does not necessarily mean the link has
been lost and should not trigger a immediate read of the status. RX sense
going high also does not require a detect cycle, as HPD going high is the
right point in time to read the EDID.

Signed-off-by: Lucas Stach <l.stach@...gutronix.de>
Reviewed-by: Neil Armstrong <narmstrong@...libre.com> (v1)
Reviewed-by: Robert Foss <robert.foss@...aro.org>
Signed-off-by: Robert Foss <robert.foss@...aro.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20220826185733.3213248-1-l.stach@pengutronix.de
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/bridge/synopsys/dw-hdmi.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
index 25d58dcfc87e..d3129a3e6ab7 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
@@ -2970,6 +2970,7 @@ static irqreturn_t dw_hdmi_irq(int irq, void *dev_id)
 {
 	struct dw_hdmi *hdmi = dev_id;
 	u8 intr_stat, phy_int_pol, phy_pol_mask, phy_stat;
+	enum drm_connector_status status = connector_status_unknown;
 
 	intr_stat = hdmi_readb(hdmi, HDMI_IH_PHY_STAT0);
 	phy_int_pol = hdmi_readb(hdmi, HDMI_PHY_POL0);
@@ -3008,13 +3009,15 @@ static irqreturn_t dw_hdmi_irq(int irq, void *dev_id)
 			cec_notifier_phys_addr_invalidate(hdmi->cec_notifier);
 			mutex_unlock(&hdmi->cec_notifier_mutex);
 		}
-	}
 
-	if (intr_stat & HDMI_IH_PHY_STAT0_HPD) {
-		enum drm_connector_status status = phy_int_pol & HDMI_PHY_HPD
-						 ? connector_status_connected
-						 : connector_status_disconnected;
+		if (phy_stat & HDMI_PHY_HPD)
+			status = connector_status_connected;
+
+		if (!(phy_stat & (HDMI_PHY_HPD | HDMI_PHY_RX_SENSE)))
+			status = connector_status_disconnected;
+	}
 
+	if (status != connector_status_unknown) {
 		dev_dbg(hdmi->dev, "EVENT=%s\n",
 			status == connector_status_connected ?
 			"plugin" : "plugout");
-- 
2.35.1