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 <redacted>
---
 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