linux-kernel - [RFC] dcss: fix attaching to sn56dsi86 bridge

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Message-Id: <20201124171956.981307-1-lukas@mntre.com>
Date:   Tue, 24 Nov 2020 18:19:57 +0100
From:   "Lukas F. Hartmann" <lukas@...re.com>
To:     lukas@...re.com
Cc:     agx@...xcpu.org, laurentiu.palcu@....com,
        Laurentiu Palcu <laurentiu.palcu@....nxp.com>,
        Lucas Stach <l.stach@...gutronix.de>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        dri-devel@...ts.freedesktop.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: [RFC] dcss: fix attaching to sn56dsi86 bridge

The sn56dsi86 DSI to eDP bridge driver does not support attaching
without a drm connector. This patch makes the attachment work. Required
for the display chain in MNT Reform 2.0 (DCSS->NWL DSI->SN56DSI86->EDP).

Signed-off-by: Lukas F. Hartmann <lukas@...re.com>
---
 drivers/gpu/drm/imx/dcss/dcss-kms.c | 15 ++++++++-------
 1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/imx/dcss/dcss-kms.c b/drivers/gpu/drm/imx/dcss/dcss-kms.c
index 135a62366..4967f828b 100644
--- a/drivers/gpu/drm/imx/dcss/dcss-kms.c
+++ b/drivers/gpu/drm/imx/dcss/dcss-kms.c
@@ -82,6 +82,7 @@ static int dcss_kms_bridge_connector_init(struct dcss_kms_dev *kms)
 	struct drm_crtc *crtc = (struct drm_crtc *)&kms->crtc;
 	struct drm_panel *panel;
 	struct drm_bridge *bridge;
+	struct drm_connector_list_iter iter;
 	int ret;

 	ret = drm_of_find_panel_or_bridge(ddev->dev->of_node, 0, 0,
@@ -104,19 +105,19 @@ static int dcss_kms_bridge_connector_init(struct dcss_kms_dev *kms)
 		return ret;
 	}

-	ret = drm_bridge_attach(encoder, bridge, NULL,
-				DRM_BRIDGE_ATTACH_NO_CONNECTOR);
+	ret = drm_bridge_attach(encoder, bridge, NULL, 0);
 	if (ret < 0) {
 		dev_err(ddev->dev, "Unable to attach bridge %pOF\n",
 			bridge->of_node);
 		return ret;
 	}

-	kms->connector = drm_bridge_connector_init(ddev, encoder);
-	if (IS_ERR(kms->connector)) {
-		dev_err(ddev->dev, "Unable to create bridge connector.\n");
-		return PTR_ERR(kms->connector);
-	}
+	/*
+	 * This hack to look up the connector is copied from mxsfb.
+	 */
+	drm_connector_list_iter_begin(ddev, &iter);
+	kms->connector = drm_connector_list_iter_next(&iter);
+	drm_connector_list_iter_end(&iter);

 	drm_connector_attach_encoder(kms->connector, encoder);

--
2.28.0