[PATCH v2 3/4] drm/sun4i: tcon: Support the LVDS Dual-Link on the A20

[Maxime Ripard <maxime@cerno.tech>]

The A20 can use its second TCON as the secondary LVDS link in a dual-link
setup, with the TCON0 being the main link. Extend a bit the parsing code to
leverage the DRM dual-link code, register only the LVDS output on the
primary TCON, and add the needed bits to setup the TCON properly.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
---
 drivers/gpu/drm/sun4i/sun4i_tcon.c | 36 +++++++++++++++++++++++++++++++-
 drivers/gpu/drm/sun4i/sun4i_tcon.h |  4 +++-
 2 files changed, 40 insertions(+)

diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.c b/drivers/gpu/drm/sun4i/sun4i_tcon.c
index d03ad75f9900..ed2abf6eb18b 100644
--- a/drivers/gpu/drm/sun4i/sun4i_tcon.c
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.c
@@ -487,6 +487,9 @@ static void sun4i_tcon0_mode_set_lvds(struct sun4i_tcon *tcon,
 	else
 		reg |= SUN4I_TCON0_LVDS_IF_DATA_POL_NORMAL;
 
+	if (tcon->lvds_dual_link)
+		reg |= SUN4I_TCON0_LVDS_IF_DUAL_LINK;
+
 	if (sun4i_tcon_get_pixel_depth(encoder) == 24)
 		reg |= SUN4I_TCON0_LVDS_IF_BITWIDTH_24BITS;
 	else
@@ -896,6 +899,16 @@ static int sun4i_tcon_register_panel(struct drm_device *drm,
 		return sun4i_rgb_init(drm, tcon);
 
 	/*
+	 * Only the TCON0 will be relevant for the LVDS output, so if
+	 * our ID is something else, let's prevent our TCON from
+	 * registering its own LVDS output
+	 */
+	if (tcon->id) {
+		dev_info(dev, "Secondary TCON, disabling panel output");
+		return 0;
+	}
+
+	/*
 	 * This can only be made optional since we've had DT
 	 * nodes without the LVDS reset properties.
 	 *
@@ -941,6 +954,28 @@ static int sun4i_tcon_register_panel(struct drm_device *drm,
 		return -ENODEV;
 	}
 
+	/*
+	 * If we don't have a second TCON, we will never be able to do
+	 * dual-link LVDS, so we don't have much more to do.
+	 */
+	companion = of_parse_phandle(dev->of_node, "allwinner,lvds-companion", 0);
+	if (!companion)
+		return 0;
+
+	/*
+	 * Let's do a sanity check on the dual-link setup to make sure
+	 * everything is properly described.
+	 */
+	ret = drm_of_lvds_get_dual_link_pixel_order(dev->of_node, 1, 0,
+						    companion, 1, 0);
+	if (ret < 0) {
+		dev_err(dev, "Invalid Dual-Link Configuration.\n");
+		return ret;
+	}
+
+	dev_info(dev, "Primary TCON, enabling LVDS Dual-Link");
+	tcon->lvds_dual_link = true;
+
 	return sun4i_lvds_init(drm, tcon);
 }
 
@@ -1500,6 +1535,7 @@ static const struct sun4i_tcon_quirks sun7i_a20_tcon0_quirks = {
 };
 
 static const struct sun4i_tcon_quirks sun7i_a20_quirks = {
+	.supports_lvds		= true,
 	.has_channel_0		= true,
 	.has_channel_1		= true,
 	.dclk_min_div		= 4,
diff --git a/drivers/gpu/drm/sun4i/sun4i_tcon.h b/drivers/gpu/drm/sun4i/sun4i_tcon.h
index cfbf4e6c1679..51c4e09cdd13 100644
--- a/drivers/gpu/drm/sun4i/sun4i_tcon.h
+++ b/drivers/gpu/drm/sun4i/sun4i_tcon.h
@@ -98,6 +98,7 @@
 
 #define SUN4I_TCON0_LVDS_IF_REG			0x84
 #define SUN4I_TCON0_LVDS_IF_EN				BIT(31)
+#define SUN4I_TCON0_LVDS_IF_DUAL_LINK			BIT(30)
 #define SUN4I_TCON0_LVDS_IF_BITWIDTH_MASK		BIT(26)
 #define SUN4I_TCON0_LVDS_IF_BITWIDTH_18BITS		(1 << 26)
 #define SUN4I_TCON0_LVDS_IF_BITWIDTH_24BITS		(0 << 26)
@@ -274,6 +275,9 @@ struct sun4i_tcon {
 	/* Associated crtc */
 	struct sun4i_crtc		*crtc;
 
+	/* Is the LVDS link a dual-channel link? */
+	bool				lvds_dual_link;
+
 	int				id;
 
 	/* TCON list management */
-- 
git-series 0.9.1