linux-kernel - [PATCH 4/4] DRM: BRIDGE: TFP410: If connected, use I2C for polled HPD status.

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Message-Id: <20230125-tfp410_i2c-v1-4-66a4d4e390b7@criticallink.com>
Date:   Wed, 25 Jan 2023 16:09:12 -0500
From:   Jonathan Cormier <jcormier@...ticallink.com>
To:     Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <robert.foss@...aro.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        Jyri Sarha <jsarha@...com>
Cc:     dri-devel@...ts.freedesktop.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Michael Williamson <michael.williamson@...ticallink.com>,
        Bob Duke <bduke@...ticallink.com>,
        Jonathan Cormier <jcormier@...ticallink.com>
Subject: [PATCH 4/4] DRM: BRIDGE: TFP410: If connected, use I2C for polled HPD status.

From: Michael Williamson <michael.williamson@...ticallink.com>

If the I2C bus is connected on the TFP410, then use the register
status bit to determine connection state.  This is needed, in particular,
for polling the state when the Hot Plug detect is not connected to
a controlling CPU via GPIO/IRQ lane.

Signed-off-by: Michael Williamson <michael.williamson@...ticallink.com>
Signed-off-by: Jonathan Cormier <jcormier@...ticallink.com>
---
 drivers/gpu/drm/bridge/ti-tfp410.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/gpu/drm/bridge/ti-tfp410.c b/drivers/gpu/drm/bridge/ti-tfp410.c
index 837e1f81a0ff..ac216eaec3c8 100644
--- a/drivers/gpu/drm/bridge/ti-tfp410.c
+++ b/drivers/gpu/drm/bridge/ti-tfp410.c
@@ -28,6 +28,9 @@
 #define TFP410_BIT_BSEL BIT(2)
 #define TFP410_BIT_DSEL BIT(3)
 
+#define TFP410_REG_CTL_2_MODE	0x09
+#define TFP410_BIT_HTPLG BIT(1)
+
 static const struct regmap_config tfp410_regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 8,
@@ -105,6 +108,16 @@ static enum drm_connector_status
 tfp410_connector_detect(struct drm_connector *connector, bool force)
 {
 	struct tfp410 *dvi = drm_connector_to_tfp410(connector);
+	u32 val;
+	unsigned int ret;
+
+	if (dvi->i2c) {
+		ret = regmap_test_bits(dvi->regmap, TFP410_REG_CTL_2_MODE, TFP410_BIT_HTPLG);
+		if (ret < 0)
+			dev_err(dvi->dev, "%s failed to read HTPLG bit : %d\n", __func__, ret);
+		else
+			return ret ? connector_status_connected : connector_status_disconnected;
+	}
 
 	return drm_bridge_detect(dvi->next_bridge);
 }

-- 
2.25.1