drm/bridge: lt9611: Add support for single Port B input

The LT9611 has two DSI input ports. The driver currently assumes Port A
is always used for single-port configurations. However, some boards
connect DSI to Port B only.

Update the driver to detect which ports are populated from devicetree
and configure the hardware accordingly:

- If only port@1 (Port B) is populated, configure port swap (0x8303
  bit 6) and byte_clk source (0x8250 bit 3:2) for Port B operation
- If both ports are populated, use dual-port mode (Port A + B)
- If only port@0 (Port A) is populated, use single Port A (existing
  behavior)

Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>
Signed-off-by: Hongyang Zhao <hongyang.zhao@thundersoft.com>
Reviewed-by: Roger Shimizu <rosh@debian.org>
Tested-by: Roger Shimizu <rosh@debian.org>
Link: https://patch.msgid.link/20260207-rubikpi-next-20260116-v3-2-23b9aa189a3a@thundersoft.com
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@oss.qualcomm.com>

diff --git a/drivers/gpu/drm/bridge/lontium-lt9611.c b/drivers/gpu/drm/bridge/lontium-lt9611.c
index 0628d8e737abbfa5290e747490da2fa23b0cd317..4517aee83332a1deef84a039da7199002944c945 100644 (file)
--- a/drivers/gpu/drm/bridge/lontium-lt9611.c
+++ b/drivers/gpu/drm/bridge/lontium-lt9611.c
@@ -116,12 +116,25 @@ static int lt9611_mipi_input_digital(struct lt9611 *lt9611,
                { 0x830a, 0x00 },
                { 0x824f, 0x80 },
                { 0x8250, 0x10 },
+               { 0x8303, 0x00 },
                { 0x8302, 0x0a },
                { 0x8306, 0x0a },
        };
 
-       if (lt9611->dsi1_node)
-               reg_cfg[1].def = 0x03;
+       if (lt9611->dsi1_node) {
+               if (lt9611->dsi0_node) {
+                       /* Dual port (Port A + B) */
+                       reg_cfg[1].def = 0x03;
+               } else {
+                       /*
+                        * Single port B:
+                        * - 0x8303 bit 6: port swap (1=PortB as primary)
+                        * - 0x8250 bit 3:2: byte_clk source (01=PortB)
+                        */
+                       reg_cfg[3].def = 0x14;
+                       reg_cfg[4].def = 0x40;
+               }
+       }
 
        return regmap_multi_reg_write(lt9611->regmap, reg_cfg, ARRAY_SIZE(reg_cfg));
 }
@@ -202,7 +215,9 @@ static void lt9611_pcr_setup(struct lt9611 *lt9611, const struct drm_display_mod
        regmap_write(lt9611->regmap, 0x831d, pol);
 
        regmap_multi_reg_write(lt9611->regmap, reg_cfg, ARRAY_SIZE(reg_cfg));
-       if (lt9611->dsi1_node) {
+
+       /* dual port: configure hact for combining two DSI inputs */
+       if (lt9611->dsi0_node && lt9611->dsi1_node) {
                unsigned int hact = mode->hdisplay;
 
                hact >>= 2;
@@ -759,7 +774,8 @@ static enum drm_mode_status lt9611_bridge_mode_valid(struct drm_bridge *bridge,
        if (mode->hdisplay > 3840)
                return MODE_BAD_HVALUE;
 
-       if (mode->hdisplay > 2000 && !lt9611->dsi1_node)
+       /* high resolution requires dual port (Port A + B) */
+       if (mode->hdisplay > 2000 && !(lt9611->dsi0_node && lt9611->dsi1_node))
                return MODE_PANEL;
 
        return MODE_OK;
@@ -1033,13 +1049,13 @@ static int lt9611_parse_dt(struct device *dev,
                           struct lt9611 *lt9611)
 {
        lt9611->dsi0_node = of_graph_get_remote_node(dev->of_node, 0, -1);
-       if (!lt9611->dsi0_node) {
-               dev_err(lt9611->dev, "failed to get remote node for primary dsi\n");
+       lt9611->dsi1_node = of_graph_get_remote_node(dev->of_node, 1, -1);
+
+       if (!lt9611->dsi0_node && !lt9611->dsi1_node) {
+               dev_err(lt9611->dev, "failed to get remote node for dsi\n");
                return -ENODEV;
        }
 
-       lt9611->dsi1_node = of_graph_get_remote_node(dev->of_node, 1, -1);
-
        lt9611->ac_mode = of_property_read_bool(dev->of_node, "lt,ac-mode");
 
        return drm_of_find_panel_or_bridge(dev->of_node, 2, -1, NULL, &lt9611->next_bridge);
@@ -1161,14 +1177,16 @@ static int lt9611_probe(struct i2c_client *client)
 
        drm_bridge_add(&lt9611->bridge);
 
-       /* Attach primary DSI */
-       lt9611->dsi0 = lt9611_attach_dsi(lt9611, lt9611->dsi0_node);
-       if (IS_ERR(lt9611->dsi0)) {
-               ret = PTR_ERR(lt9611->dsi0);
-               goto err_remove_bridge;
+       /* Attach primary DSI (directly drives or Port A in dual-port mode) */
+       if (lt9611->dsi0_node) {
+               lt9611->dsi0 = lt9611_attach_dsi(lt9611, lt9611->dsi0_node);
+               if (IS_ERR(lt9611->dsi0)) {
+                       ret = PTR_ERR(lt9611->dsi0);
+                       goto err_remove_bridge;
+               }
        }
 
-       /* Attach secondary DSI, if specified */
+       /* Attach secondary DSI (Port B in single or dual-port mode) */
        if (lt9611->dsi1_node) {
                lt9611->dsi1 = lt9611_attach_dsi(lt9611, lt9611->dsi1_node);
                if (IS_ERR(lt9611->dsi1)) {