[PATCH v4 02/17] drm: bridge: dw_hdmi: Only notify connected status on HPD interrupt

[Jonas Karlman <jonas@kwiboo.se>]

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")
Reviewed-by: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
---
v4: Collect r-b tag
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 248454c45d6b..0647ec6632d8 100644
--- a/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
+++ b/drivers/gpu/drm/bridge/synopsys/dw-hdmi.c
@@ -3157,7 +3157,8 @@ 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)))
-- 
2.54.0