linux-kernel - [PATCH] drm/vc4: Fix oops dereferencing DPI's connector since panel

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Message-Id: <20180309233256.1667-1-eric@anholt.net>
Date:   Fri,  9 Mar 2018 15:32:56 -0800
From:   Eric Anholt <eric@...olt.net>
To:     dri-devel@...ts.freedesktop.org
Cc:     linux-kernel@...r.kernel.org, Eric Anholt <eric@...olt.net>,
        Boris Brezillon <boris.brezillon@...tlin.com>
Subject: [PATCH] drm/vc4: Fix oops dereferencing DPI's connector since panel_bridge.

In the cleanup, I didn't notice that we needed to dereference the
connector for the bus_format.  Fix the regression by looking up the
first (and only) connector attached to us, and assume that its
bus_format is what we want.  Some day it would be good to have that
part of display_info attached to the bridge, instead.

Signed-off-by: Eric Anholt <eric@...olt.net>
Fixes: 7b1298e05310 ("drm/vc4: Switch DPI to using the panel-bridge helper.")
Cc: Boris Brezillon <boris.brezillon@...tlin.com>
---
 drivers/gpu/drm/vc4/vc4_dpi.c | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/vc4/vc4_dpi.c b/drivers/gpu/drm/vc4/vc4_dpi.c
index 72c9dbd81d7f..88783e143cc2 100644
--- a/drivers/gpu/drm/vc4/vc4_dpi.c
+++ b/drivers/gpu/drm/vc4/vc4_dpi.c
@@ -96,7 +96,6 @@ struct vc4_dpi {
 	struct platform_device *pdev;
 
 	struct drm_encoder *encoder;
-	struct drm_connector *connector;
 
 	void __iomem *regs;
 
@@ -164,14 +163,31 @@ static void vc4_dpi_encoder_disable(struct drm_encoder *encoder)
 
 static void vc4_dpi_encoder_enable(struct drm_encoder *encoder)
 {
+	struct drm_device *dev = encoder->dev;
 	struct drm_display_mode *mode = &encoder->crtc->mode;
 	struct vc4_dpi_encoder *vc4_encoder = to_vc4_dpi_encoder(encoder);
 	struct vc4_dpi *dpi = vc4_encoder->dpi;
+	struct drm_connector_list_iter conn_iter;
+	struct drm_connector *connector = NULL, *connector_scan;
 	u32 dpi_c = DPI_ENABLE | DPI_OUTPUT_ENABLE_MODE;
 	int ret;
 
-	if (dpi->connector->display_info.num_bus_formats) {
-		u32 bus_format = dpi->connector->display_info.bus_formats[0];
+	/* Look up the connector attached to DPI so we can get the
+	 * bus_format.  Ideally the bridge would tell us the
+	 * bus_format we want, but it doesn't yet, so assume that it's
+	 * uniform throughout the bridge chain.
+	 */
+	drm_connector_list_iter_begin(dev, &conn_iter);
+	drm_for_each_connector_iter(connector_scan, &conn_iter) {
+		if (connector_scan->encoder == encoder) {
+			connector = connector_scan;
+			break;
+		}
+	}
+	drm_connector_list_iter_end(&conn_iter);
+
+	if (connector && connector->display_info.num_bus_formats) {
+		u32 bus_format = connector->display_info.bus_formats[0];
 
 		switch (bus_format) {
 		case MEDIA_BUS_FMT_RGB888_1X24:
@@ -199,6 +215,9 @@ static void vc4_dpi_encoder_enable(struct drm_encoder *encoder)
 			DRM_ERROR("Unknown media bus format %d\n", bus_format);
 			break;
 		}
+	} else {
+		/* Default to 24bit if no connector found. */
+		dpi_c |= VC4_SET_FIELD(DPI_FORMAT_24BIT_888_RGB, DPI_FORMAT);
 	}
 
 	if (mode->flags & DRM_MODE_FLAG_NHSYNC)
@@ -264,7 +283,7 @@ static int vc4_dpi_init_bridge(struct vc4_dpi *dpi)
 			return ret;
 	}
 
-	if (panel)
+	if (panel) 
 		bridge = drm_panel_bridge_add(panel, DRM_MODE_CONNECTOR_DPI);
 
 	return drm_bridge_attach(dpi->encoder, bridge, NULL);
-- 
2.16.2