linux-kernel - [PATCH AUTOSEL 6.0 12/44] drm: bridge: dw_hdmi: only trigger hotplug event on link change

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Date:   Sun,  9 Oct 2022 19:49:00 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Lucas Stach <l.stach@...gutronix.de>,
        Neil Armstrong <narmstrong@...libre.com>,
        Robert Foss <robert.foss@...aro.org>,
        Sasha Levin <sashal@...nel.org>, andrzej.hajda@...el.com,
        neil.armstrong@...aro.org, airlied@...il.com, daniel@...ll.ch,
        Sandor.yu@....com, ville.syrjala@...ux.intel.com,
        tzimmermann@...e.de, maxime@...no.tech,
        dri-devel@...ts.freedesktop.org
Subject: [PATCH AUTOSEL 6.0 12/44] 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 25a60eb4d67c..40d8ca37f5bc 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
@@ -3096,6 +3096,7 @@ 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);
@@ -3134,13 +3135,15 @@ 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