Up till now, the OLDI support in tidss was integrated within the tidss dispc.
This was fine till the OLDI was one-to-mapped with the DSS video-port (VP).
The AM62 and AM62P SoCs have 2 OLDI TXes that can support dual-lvds / lvds-clone
modes.

Add OLDI TXes as separate DRM bridge entities to better support the new LVDS
configurations.

Signed-off-by: Aradhya Bhatia <a-bhat...@ti.com>
---
Note:

The OLDI configuration should happen before the video-port configuration takes
place in tidss_crtc_atomic_enable hook. I have posted a patch allowing DRM
bridges to get enabled before the CRTC of that bridge is enabled[0]. This patch
uses the bridge hooks introduced in [0], and hence will not compile without [0].

[0]: Dependency Patch: Introduce early_enable / late_disable drm bridge APIs
https://lore.kernel.org/all/20240511153051.1355825-7-a-bhat...@ti.com/

---
 drivers/gpu/drm/tidss/Makefile      |   3 +-
 drivers/gpu/drm/tidss/tidss_dispc.c |  11 +-
 drivers/gpu/drm/tidss/tidss_dispc.h |   4 +
 drivers/gpu/drm/tidss/tidss_drv.c   |  13 +-
 drivers/gpu/drm/tidss/tidss_drv.h   |   4 +
 drivers/gpu/drm/tidss/tidss_oldi.c  | 568 ++++++++++++++++++++++++++++
 drivers/gpu/drm/tidss/tidss_oldi.h  |  73 ++++
 7 files changed, 673 insertions(+), 3 deletions(-)
 create mode 100644 drivers/gpu/drm/tidss/tidss_oldi.c
 create mode 100644 drivers/gpu/drm/tidss/tidss_oldi.h

diff --git a/drivers/gpu/drm/tidss/Makefile b/drivers/gpu/drm/tidss/Makefile
index 312645271014..b6d6becf1683 100644
--- a/drivers/gpu/drm/tidss/Makefile
+++ b/drivers/gpu/drm/tidss/Makefile
@@ -7,6 +7,7 @@ tidss-y := tidss_crtc.o \
        tidss_irq.o \
        tidss_plane.o \
        tidss_scale_coefs.o \
-       tidss_dispc.o
+       tidss_dispc.o \
+       tidss_oldi.o
 
 obj-$(CONFIG_DRM_TIDSS) += tidss.o
diff --git a/drivers/gpu/drm/tidss/tidss_dispc.c 
b/drivers/gpu/drm/tidss/tidss_dispc.c
index 1ad711f8d2a8..4961da3989c0 100644
--- a/drivers/gpu/drm/tidss/tidss_dispc.c
+++ b/drivers/gpu/drm/tidss/tidss_dispc.c
@@ -466,6 +466,16 @@ static u32 dispc_vp_read(struct dispc_device *dispc, u32 
hw_videoport, u16 reg)
        return ioread32(base + reg);
 }
 
+u32 tidss_get_status(struct tidss_device *tidss)
+{
+       return dispc_read(tidss->dispc, DSS_SYSSTATUS);
+}
+
+void tidss_configure_oldi(struct tidss_device *tidss, u32 hw_videoport, u32 
val)
+{
+       return dispc_vp_write(tidss->dispc, hw_videoport, 
DISPC_VP_DSS_OLDI_CFG, val);
+}
+
 /*
  * TRM gives bitfields as start:end, where start is the higher bit
  * number. For example 7:0
@@ -1310,7 +1320,6 @@ void dispc_vp_disable_clk(struct dispc_device *dispc, u32 
hw_videoport)
  * Calculate the percentage difference between the requested pixel clock rate
  * and the effective rate resulting from calculating the clock divider value.
  */
-static
 unsigned int dispc_pclk_diff(unsigned long rate, unsigned long real_rate)
 {
        int r = rate / 100, rr = real_rate / 100;
diff --git a/drivers/gpu/drm/tidss/tidss_dispc.h 
b/drivers/gpu/drm/tidss/tidss_dispc.h
index 086327d51a90..800a73457aff 100644
--- a/drivers/gpu/drm/tidss/tidss_dispc.h
+++ b/drivers/gpu/drm/tidss/tidss_dispc.h
@@ -94,6 +94,10 @@ extern const struct dispc_features dispc_am62a7_feats;
 extern const struct dispc_features dispc_am65x_feats;
 extern const struct dispc_features dispc_j721e_feats;
 
+u32 tidss_get_status(struct tidss_device *tidss);
+void tidss_configure_oldi(struct tidss_device *tidss, u32 hw_videoport, u32 
val);
+unsigned int dispc_pclk_diff(unsigned long rate, unsigned long real_rate);
+
 void dispc_set_irqenable(struct dispc_device *dispc, dispc_irq_t mask);
 dispc_irq_t dispc_read_and_clear_irqstatus(struct dispc_device *dispc);
 
diff --git a/drivers/gpu/drm/tidss/tidss_drv.c 
b/drivers/gpu/drm/tidss/tidss_drv.c
index d15f836dca95..fd90e8498cc2 100644
--- a/drivers/gpu/drm/tidss/tidss_drv.c
+++ b/drivers/gpu/drm/tidss/tidss_drv.c
@@ -23,6 +23,7 @@
 #include "tidss_drv.h"
 #include "tidss_kms.h"
 #include "tidss_irq.h"
+#include "tidss_oldi.h"
 
 /* Power management */
 
@@ -140,10 +141,17 @@ static int tidss_probe(struct platform_device *pdev)
 
        spin_lock_init(&tidss->wait_lock);
 
+       ret = tidss_oldi_init(tidss);
+       if (ret) {
+               if (ret != -EPROBE_DEFER)
+                       dev_err(dev, "failed to init OLDI (%d)\n", ret);
+               return ret;
+       }
+
        ret = dispc_init(tidss);
        if (ret) {
                dev_err(dev, "failed to initialize dispc: %d\n", ret);
-               return ret;
+               goto err_oldi_deinit;
        }
 
        pm_runtime_enable(dev);
@@ -202,6 +210,9 @@ static int tidss_probe(struct platform_device *pdev)
        pm_runtime_dont_use_autosuspend(dev);
        pm_runtime_disable(dev);
 
+err_oldi_deinit:
+       tidss_oldi_deinit(tidss);
+
        return ret;
 }
 
diff --git a/drivers/gpu/drm/tidss/tidss_drv.h 
b/drivers/gpu/drm/tidss/tidss_drv.h
index d7f27b0b0315..4ccdc177d171 100644
--- a/drivers/gpu/drm/tidss/tidss_drv.h
+++ b/drivers/gpu/drm/tidss/tidss_drv.h
@@ -11,6 +11,7 @@
 
 #define TIDSS_MAX_PORTS 4
 #define TIDSS_MAX_PLANES 4
+#define TIDSS_MAX_OLDI_TXES 2
 
 typedef u32 dispc_irq_t;
 
@@ -27,6 +28,9 @@ struct tidss_device {
        unsigned int num_planes;
        struct drm_plane *planes[TIDSS_MAX_PLANES];
 
+       unsigned int num_oldis;
+       struct tidss_oldi *oldis[TIDSS_MAX_OLDI_TXES];
+
        unsigned int irq;
 
        spinlock_t wait_lock;   /* protects the irq masks */
diff --git a/drivers/gpu/drm/tidss/tidss_oldi.c 
b/drivers/gpu/drm/tidss/tidss_oldi.c
new file mode 100644
index 000000000000..fd96ca815542
--- /dev/null
+++ b/drivers/gpu/drm/tidss/tidss_oldi.c
@@ -0,0 +1,568 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2023 - Texas Instruments Incorporated
+ *
+ * Aradhya Bhatia <a-bha...@ti.com>
+ */
+
+#include <linux/clk.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/of_graph.h>
+#include <linux/mfd/syscon.h>
+#include <linux/media-bus-format.h>
+#include <linux/regmap.h>
+
+#include <drm/drm_atomic_helper.h>
+#include <drm/drm_bridge.h>
+#include <drm/drm_panel.h>
+#include <drm/drm_of.h>
+#include <drm/drm_crtc.h>
+#include <drm/drm_probe_helper.h>
+
+#include "tidss_drv.h"
+#include "tidss_oldi.h"
+
+struct tidss_oldi {
+       struct tidss_device     *tidss;
+       struct device           *dev;
+
+       struct drm_bridge       bridge;
+       struct drm_bridge       *next_bridge;
+
+       struct drm_panel *panel;
+
+       enum tidss_oldi_link_type link_type;
+       const struct oldi_bus_format *bus_format;
+       u32 oldi_instance;
+       u32 parent_vp;
+
+       struct clk *s_clk;
+       struct regmap *io_ctrl;
+};
+
+static const struct oldi_bus_format oldi_bus_formats[] = {
+       { MEDIA_BUS_FMT_RGB666_1X7X3_SPWG,      18, SPWG_18,    
MEDIA_BUS_FMT_RGB666_1X18 },
+       { MEDIA_BUS_FMT_RGB888_1X7X4_SPWG,      24, SPWG_24,    
MEDIA_BUS_FMT_RGB888_1X24 },
+       { MEDIA_BUS_FMT_RGB888_1X7X4_JEIDA,     24, JEIDA_24,   
MEDIA_BUS_FMT_RGB888_1X24 },
+};
+
+static inline struct tidss_oldi *
+drm_bridge_to_tidss_oldi(struct drm_bridge *bridge)
+{
+       return container_of(bridge, struct tidss_oldi, bridge);
+}
+
+static int tidss_oldi_bridge_attach(struct drm_bridge *bridge,
+                                   enum drm_bridge_attach_flags flags)
+{
+       struct tidss_oldi *oldi = drm_bridge_to_tidss_oldi(bridge);
+
+       if (!oldi->next_bridge) {
+               dev_err(oldi->dev,
+                       "%s: OLDI%d Failure attach next bridge\n",
+                       __func__, oldi->oldi_instance);
+               return -ENODEV;
+       }
+
+       if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR)) {
+               dev_err(oldi->dev,
+                       "%s: OLDI%d DRM_BRIDGE_ATTACH_NO_CONNECTOR is 
mandatory.\n",
+                       __func__, oldi->oldi_instance);
+               return -EINVAL;
+       }
+
+       return drm_bridge_attach(bridge->encoder, oldi->next_bridge,
+                                bridge, flags);
+}
+
+static int
+oldi_set_serial_clk(struct tidss_oldi *oldi, unsigned long rate)
+{
+       unsigned long new_rate;
+       int ret;
+
+       ret = clk_set_rate(oldi->s_clk, rate);
+       if (ret) {
+               dev_err(oldi->dev,
+                       "OLDI%d: failed to set serial clk rate to %lu Hz\n",
+                        oldi->oldi_instance, rate);
+               return ret;
+       }
+
+       new_rate = clk_get_rate(oldi->s_clk);
+
+       if (dispc_pclk_diff(rate, new_rate) > 5)
+               dev_warn(oldi->dev,
+                        "OLDI%d Clock rate %lu differs over 5%% from requested 
%lu\n",
+                        oldi->oldi_instance, new_rate, rate);
+
+       dev_dbg(oldi->dev, "OLDI%d: new rate %lu Hz (requested %lu Hz)\n",
+               oldi->oldi_instance, clk_get_rate(oldi->s_clk), rate);
+
+       return 0;
+}
+
+static void tidss_oldi_tx_power(struct tidss_oldi *oldi, bool power)
+{
+       u32 val = 0, mask;
+
+       if (WARN_ON(!oldi->io_ctrl))
+               return;
+
+       /*
+        * The power control bits are Active Low, and remain powered off by
+        * default. That is, the bits are set to 1. To power on the OLDI TXes,
+        * the bits must be cleared to 0. Since there are cases where not all
+        * OLDI TXes are being used, the power logic selectively powers them
+        * on.
+        * Setting the variable 'val' to particular bit masks, makes sure that
+        * the unrequired OLDI TXes remain powered off.
+        */
+
+       if (power) {
+               val = 0;
+               switch (oldi->link_type) {
+               case OLDI_MODE_SINGLE_LINK:
+                       if (oldi->oldi_instance == OLDI(0))
+                               mask = OLDI_PWRDN_TX(0) | OLDI_PWRDN_BG;
+                       else if (oldi->oldi_instance == OLDI(1))
+                               mask = OLDI_PWRDN_TX(1) | OLDI_PWRDN_BG;
+
+                       break;
+               case OLDI_MODE_CLONE_SINGLE_LINK:
+               case OLDI_MODE_DUAL_LINK:
+                       mask = OLDI_PWRDN_TX(0) | OLDI_PWRDN_TX(1) | 
OLDI_PWRDN_BG;
+                       break;
+               default:
+                       if (oldi->oldi_instance == OLDI(0))
+                               mask = OLDI_PWRDN_TX(0);
+                       else if (oldi->oldi_instance == OLDI(1))
+                               mask = OLDI_PWRDN_TX(1);
+
+                       val = mask;
+                       break;
+               }
+       } else {
+               switch (oldi->link_type) {
+               case OLDI_MODE_CLONE_SINGLE_LINK:
+               case OLDI_MODE_DUAL_LINK:
+                       mask = OLDI_PWRDN_TX(0) | OLDI_PWRDN_TX(1) | 
OLDI_PWRDN_BG;
+                       break;
+               case OLDI_MODE_SINGLE_LINK:
+               default:
+                       if (oldi->oldi_instance == OLDI(0))
+                               mask = OLDI_PWRDN_TX(0);
+                       else if (oldi->oldi_instance == OLDI(1))
+                               mask = OLDI_PWRDN_TX(1);
+
+                       break;
+               }
+               val = mask;
+       }
+
+       regmap_update_bits(oldi->io_ctrl, OLDI_PD_CTRL, mask, val);
+}
+
+static int tidss_oldi_config(struct tidss_oldi *oldi)
+{
+       const struct oldi_bus_format *bus_fmt = NULL;
+       u32 oldi_reset_bit = BIT(5);
+       int count = 0;
+       u32 oldi_cfg = 0;
+
+       bus_fmt = oldi->bus_format;
+
+       /*
+        * MASTERSLAVE and SRC bits of OLDI Config are always set to 0.
+        */
+
+       if (bus_fmt->data_width == 24)
+               oldi_cfg |= OLDI_MSB;
+       else if (bus_fmt->data_width != 18)
+               dev_warn(oldi->dev,
+                        "OLDI%d: DSS port width %d not supported\n",
+                        oldi->oldi_instance, bus_fmt->data_width);
+
+       oldi_cfg |= OLDI_DEPOL;
+
+       oldi_cfg = (oldi_cfg & (~OLDI_MAP)) | (bus_fmt->oldi_mode_reg_val << 1);
+
+       oldi_cfg |= OLDI_SOFTRST;
+
+       oldi_cfg |= OLDI_ENABLE;
+
+       switch (oldi->link_type) {
+       case OLDI_MODE_SINGLE_LINK:
+               /* All configuration is done for this mode.  */
+               break;
+
+       case OLDI_MODE_CLONE_SINGLE_LINK:
+               oldi_cfg |= OLDI_CLONE_MODE;
+               break;
+
+       case OLDI_MODE_DUAL_LINK:
+               /* data-mapping field also indicates dual-link mode */
+               oldi_cfg |= BIT(3);
+               oldi_cfg |= OLDI_DUALMODESYNC;
+               break;
+
+       default:
+               dev_err(oldi->dev, "OLDI%d: Unsupported mode.\n",
+                       oldi->oldi_instance);
+               return -EINVAL;
+       }
+
+       tidss_configure_oldi(oldi->tidss, oldi->parent_vp, oldi_cfg);
+       while (!(oldi_reset_bit & tidss_get_status(oldi->tidss)) &&
+              count < 10000)
+               count++;
+
+       if (!(oldi_reset_bit & tidss_get_status(oldi->tidss)))
+               dev_warn(oldi->dev, "%s: OLDI%d timeout waiting OLDI reset 
done\n",
+                        __func__, oldi->oldi_instance);
+
+       return 0;
+}
+
+static void tidss_oldi_atomic_early_enable(struct drm_bridge *bridge,
+                                          struct drm_bridge_state 
*old_bridge_state)
+{
+       struct tidss_oldi *oldi = drm_bridge_to_tidss_oldi(bridge);
+       struct drm_atomic_state *state = old_bridge_state->base.state;
+       struct drm_connector *connector;
+       struct drm_connector_state *conn_state;
+       struct drm_crtc_state *crtc_state;
+       struct drm_display_mode *mode;
+
+       connector = drm_atomic_get_new_connector_for_encoder(state,
+                                                            bridge->encoder);
+       if (WARN_ON(!connector))
+               return;
+
+       conn_state = drm_atomic_get_new_connector_state(state, connector);
+       if (WARN_ON(!conn_state))
+               return;
+
+       crtc_state = drm_atomic_get_new_crtc_state(state, conn_state->crtc);
+       if (WARN_ON(!crtc_state))
+               return;
+
+       mode = &crtc_state->adjusted_mode;
+
+       /* Configure the OLDI params*/
+       tidss_oldi_config(oldi);
+
+       /* Enable the OLDI serial clock (7 times the pixel clock) */
+       oldi_set_serial_clk(oldi, mode->clock * 7 * 1000);
+
+       /* Enable OLDI IO power */
+       tidss_oldi_tx_power(oldi, true);
+}
+
+static void tidss_oldi_atomic_late_disable(struct drm_bridge *bridge,
+                                          struct drm_bridge_state 
*old_bridge_state)
+{
+       struct tidss_oldi *oldi = drm_bridge_to_tidss_oldi(bridge);
+
+       /* Disable OLDI IO power */
+       tidss_oldi_tx_power(oldi, false);
+
+       /* Disable OLDI clock by setting IDLE Frequency */
+       oldi_set_serial_clk(oldi, OLDI_IDLE_CLK_HZ);
+
+       /* Clear OLDI Config */
+       tidss_configure_oldi(oldi->tidss, oldi->parent_vp, 0);
+}
+
+#define MAX_INPUT_SEL_FORMATS  1
+
+static u32 *tidss_oldi_atomic_get_input_bus_fmts(struct drm_bridge *bridge,
+                                                struct drm_bridge_state 
*bridge_state,
+                                                struct drm_crtc_state 
*crtc_state,
+                                                struct drm_connector_state 
*conn_state,
+                                                u32 output_fmt,
+                                                unsigned int *num_input_fmts)
+{
+       struct tidss_oldi *oldi = drm_bridge_to_tidss_oldi(bridge);
+       u32 *input_fmts;
+       int i;
+
+       *num_input_fmts = 0;
+
+       for (i = 0; i < ARRAY_SIZE(oldi_bus_formats); i++)
+               if (oldi_bus_formats[i].bus_fmt == output_fmt)
+                       break;
+
+       if (i == ARRAY_SIZE(oldi_bus_formats))
+               return NULL;
+
+       input_fmts = kcalloc(MAX_INPUT_SEL_FORMATS, sizeof(*input_fmts),
+                            GFP_KERNEL);
+       if (!input_fmts)
+               return NULL;
+
+       *num_input_fmts = 1;
+       input_fmts[0] = oldi_bus_formats[i].input_bus_fmt;
+       oldi->bus_format = &oldi_bus_formats[i];
+
+       return input_fmts;
+}
+
+static int tidss_oldi_atomic_check(struct drm_bridge *bridge,
+                                  struct drm_bridge_state *bridge_state,
+                                  struct drm_crtc_state *crtc_state,
+                                  struct drm_connector_state *conn_state)
+{
+       /*
+        * There might be flags negotiation supported in future but
+        * set the bus flags in atomic_check statically for now.
+        */
+
+       /* Not sure what this is required for, at the moment */
+       bridge_state->input_bus_cfg.flags = bridge->timings->input_bus_flags;
+
+       return 0;
+}
+
+static const struct drm_bridge_funcs tidss_oldi_bridge_funcs = {
+       .attach         = tidss_oldi_bridge_attach,
+       .atomic_check   = tidss_oldi_atomic_check,
+       .atomic_early_enable = tidss_oldi_atomic_early_enable,
+       .atomic_late_disable = tidss_oldi_atomic_late_disable,
+       .atomic_get_input_bus_fmts = tidss_oldi_atomic_get_input_bus_fmts,
+       .atomic_duplicate_state = drm_atomic_helper_bridge_duplicate_state,
+       .atomic_destroy_state = drm_atomic_helper_bridge_destroy_state,
+       .atomic_reset = drm_atomic_helper_bridge_reset,
+};
+
+static int get_oldi_mode(struct device_node *oldi_tx)
+{
+       struct device_node *companion;
+       struct device_node *port0, *port1;
+       int pixel_order;
+
+       /*
+        * Find if the OLDI is paired with another OLDI for combined OLDI
+        * operation (dual-lvds or clone).
+        */
+       companion = of_parse_phandle(oldi_tx, "ti,companion-oldi", 0);
+       if (!companion) {
+               if (of_property_read_bool(oldi_tx, "ti,secondary-oldi"))
+                       return OLDI_MODE_SECONDARY;
+
+               /*
+                * The OLDI TX does not have a companion, nor is it a
+                * secondary OLDI. It will operate independently.
+                */
+               return OLDI_MODE_SINGLE_LINK;
+       }
+
+       /*
+        * We need to work out if the sink is expecting us to function in
+        * dual-link mode. We do this by looking at the DT port nodes we are
+        * connected to, if they are marked as expecting even pixels and
+        * odd pixels than we need to enable vertical stripe output.
+        */
+       port0 = of_graph_get_port_by_id(oldi_tx, 1);
+       port1 = of_graph_get_port_by_id(companion, 1);
+       pixel_order = drm_of_lvds_get_dual_link_pixel_order(port0, port1);
+       of_node_put(port0);
+       of_node_put(port1);
+       of_node_put(companion);
+
+       switch (pixel_order) {
+       case -EINVAL:
+               /*
+                * The dual link properties were not found in at least
+                * one of the sink nodes. Since 2 OLDI ports are present
+                * in the DT, it can be safely assumed that the required
+                * configuration is Clone Mode.
+                */
+               return OLDI_MODE_CLONE_SINGLE_LINK;
+
+       case DRM_LVDS_DUAL_LINK_ODD_EVEN_PIXELS:
+               return OLDI_MODE_DUAL_LINK;
+
+       /* Unsupported OLDI Modes */
+       case DRM_LVDS_DUAL_LINK_EVEN_ODD_PIXELS:
+       default:
+               return OLDI_MODE_UNSUPPORTED;
+       }
+}
+
+static u32 get_parent_dss_vp(struct device_node *oldi_tx, u32 *parent_vp)
+{
+       struct device_node *ep, *dss_port;
+       int ret = 0;
+
+       ep = of_graph_get_endpoint_by_regs(oldi_tx, OLDI_INPUT_PORT, -1);
+       if (ep) {
+               dss_port = of_graph_get_remote_port(ep);
+               if (!dss_port) {
+                       ret = -ENODEV;
+                       goto err_return_ep_port;
+               }
+
+               ret = of_property_read_u32(dss_port, "reg", parent_vp);
+
+               of_node_put(dss_port);
+err_return_ep_port:
+               of_node_put(ep);
+               return ret;
+       }
+
+       return -ENODEV;
+}
+
+static const struct drm_bridge_timings default_tidss_oldi_timings = {
+       .input_bus_flags = DRM_BUS_FLAG_SYNC_SAMPLE_NEGEDGE
+                        | DRM_BUS_FLAG_DE_HIGH,
+};
+
+void tidss_oldi_deinit(struct tidss_device *tidss)
+{
+       for (int i = 0; i < tidss->num_oldis; i++) {
+               if (tidss->oldis[i]) {
+                       drm_bridge_remove(&tidss->oldis[i]->bridge);
+                       tidss->oldis[i] = NULL;
+               }
+       }
+}
+
+int tidss_oldi_init(struct tidss_device *tidss)
+{
+       struct tidss_oldi *oldi;
+       struct device_node *child;
+       struct drm_bridge *bridge;
+       struct drm_panel *panel;
+       u32 parent_vp, oldi_instance;
+       enum tidss_oldi_link_type link_type = OLDI_MODE_UNSUPPORTED;
+       struct device_node *oldi_parent;
+       int ret = 0;
+
+       tidss->num_oldis = 0;
+
+       oldi_parent = of_get_child_by_name(tidss->dev->of_node, "oldi-txes");
+       if (!oldi_parent)
+               /* Return gracefully */
+               return 0;
+
+       for_each_child_of_node(oldi_parent, child) {
+               ret = get_parent_dss_vp(child, &parent_vp);
+               if (ret) {
+                       if (ret == -ENODEV) {
+                               /*
+                                * ENODEV means that this particular OLDI node
+                                * is not connected with the DSS, which is not
+                                * a harmful case. There could be another OLDI
+                                * which may still be connected.
+                                * Continue to search for that.
+                                */
+                               ret = 0;
+                               continue;
+                       }
+                       goto err_put_node;
+               }
+
+               ret = of_property_read_u32(child, "reg", &oldi_instance);
+               if (ret)
+                       goto err_put_node;
+
+               /*
+                * Now that its confirmed that OLDI is connected with DSS, let's
+                * continue getting the OLDI sinks ahead and other OLDI
+                * properties.
+                */
+               ret = drm_of_find_panel_or_bridge(child, OLDI_OURPUT_PORT, -1,
+                                                 &panel, &bridge);
+               if (ret) {
+                       /*
+                        * Either there was no OLDI sink in the devicetree, or
+                        * the OLDI sink has not been added yet. In any case,
+                        * return.
+                        * We don't want to have an OLDI node connected to DSS
+                        * but not to any sink.
+                        */
+                       if (ret != -EPROBE_DEFER)
+                               dev_err(tidss->dev,
+                                       "no panel/bridge for OLDI%d. Error 
%d\n",
+                                       oldi_instance, ret);
+                       goto err_put_node;
+               }
+
+               if (panel) {
+                       bridge = devm_drm_panel_bridge_add(tidss->dev, panel);
+                       if (IS_ERR(bridge)) {
+                               ret = PTR_ERR(bridge);
+                               goto err_put_node;
+                       }
+               }
+
+               link_type = get_oldi_mode(child);
+               if (link_type == OLDI_MODE_UNSUPPORTED) {
+                       dev_err(tidss->dev,
+                               "OLDI%d: Unsupported OLDI connection.\n",
+                               oldi_instance);
+                       ret = -EINVAL;
+                       goto err_put_node;
+               } else if (link_type == OLDI_MODE_SECONDARY) {
+                       /*
+                        * This is the secondary OLDI node, which serves as a
+                        * companinon to the primary OLDI, when it is configured
+                        * for the dual-lvds mode. Since the primary OLDI will
+                        * be a part of bridge chain, no need to put this one
+                        * too. Continue onto the next OLDI node.
+                        */
+                       continue;
+               }
+
+               oldi = devm_kzalloc(tidss->dev, sizeof(*oldi), GFP_KERNEL);
+               if (!oldi) {
+                       ret = -ENOMEM;
+                       goto err_put_node;
+               }
+
+               oldi->link_type = link_type;
+               oldi->oldi_instance = oldi_instance;
+               oldi->dev = tidss->dev;
+               oldi->next_bridge = bridge;
+               oldi->panel = panel;
+
+               oldi->io_ctrl = syscon_regmap_lookup_by_phandle(child,
+                                                               
"ti,oldi-io-ctrl");
+               if (IS_ERR(oldi->io_ctrl)) {
+                       dev_err(oldi->dev,
+                               "%s: oldi%d syscon_regmap_lookup_by_phandle 
failed %ld\n",
+                              __func__, oldi_instance, PTR_ERR(oldi->io_ctrl));
+                       ret = PTR_ERR(oldi->io_ctrl);
+                       goto err_put_node;
+               }
+
+               oldi->s_clk = of_clk_get_by_name(child, "s_clk");
+               if (IS_ERR(oldi->s_clk)) {
+                       dev_err(oldi->dev,
+                               "%s: oldi%d Failed to get s_clk: %ld\n",
+                               __func__, oldi_instance, PTR_ERR(oldi->s_clk));
+                       ret = PTR_ERR(oldi->s_clk);
+                       goto err_put_node;
+               }
+
+               /* Register the bridge. */
+               oldi->bridge.of_node = child;
+               oldi->bridge.driver_private = oldi;
+               oldi->bridge.funcs = &tidss_oldi_bridge_funcs;
+               oldi->bridge.timings = &default_tidss_oldi_timings;
+
+               tidss->oldis[tidss->num_oldis++] = oldi;
+               oldi->tidss = tidss;
+
+               drm_bridge_add(&oldi->bridge);
+       }
+
+err_put_node:
+       of_node_put(child);
+       of_node_put(oldi_parent);
+       return ret;
+}
diff --git a/drivers/gpu/drm/tidss/tidss_oldi.h 
b/drivers/gpu/drm/tidss/tidss_oldi.h
new file mode 100644
index 000000000000..5ad02ddea11a
--- /dev/null
+++ b/drivers/gpu/drm/tidss/tidss_oldi.h
@@ -0,0 +1,73 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * Copyright (C) 2023 - Texas Instruments Incorporated
+ *
+ * Aradhya Bhatia <a-bha...@ti.com>
+ */
+
+#ifndef __TIDSS_OLDI_H__
+#define __TIDSS_OLDI_H__
+
+#include <linux/media-bus-format.h>
+
+#include "tidss_drv.h"
+#include "tidss_dispc.h"
+
+struct tidss_oldi;
+
+/* OLDI Instances */
+#define OLDI(n)                n
+
+/* OLDI PORTS */
+#define OLDI_INPUT_PORT                0
+#define OLDI_OURPUT_PORT       1
+
+/* OLDI Config Bits */
+#define OLDI_ENABLE            BIT(0)
+#define OLDI_MAP               (BIT(1) | BIT(2) | BIT(3))
+#define OLDI_SRC               BIT(4)
+#define OLDI_CLONE_MODE                BIT(5)
+#define OLDI_MASTERSLAVE       BIT(6)
+#define OLDI_DEPOL             BIT(7)
+#define OLDI_MSB               BIT(8)
+#define OLDI_LBEN              BIT(9)
+#define OLDI_LBDATA            BIT(10)
+#define OLDI_DUALMODESYNC      BIT(11)
+#define OLDI_SOFTRST           BIT(12)
+#define OLDI_TPATCFG           BIT(13)
+
+/* Control MMR Register */
+
+/* Register offsets */
+#define OLDI_PD_CTRL            0x100
+#define OLDI_LB_CTRL            0x104
+
+/* Power control bits */
+#define OLDI_PWRDN_TX(n)       BIT(n)
+
+/* LVDS Bandgap reference Enable/Disable */
+#define OLDI_PWRDN_BG          BIT(8)
+
+#define OLDI_IDLE_CLK_HZ       25000000 /*25 MHz */
+
+enum tidss_oldi_link_type {
+       OLDI_MODE_UNSUPPORTED,
+       OLDI_MODE_SINGLE_LINK,
+       OLDI_MODE_CLONE_SINGLE_LINK,
+       OLDI_MODE_DUAL_LINK,
+       OLDI_MODE_SECONDARY,
+};
+
+enum oldi_mode_reg_val { SPWG_18 = 0, JEIDA_24 = 1, SPWG_24 = 2 };
+
+struct oldi_bus_format {
+       u32 bus_fmt;
+       u32 data_width;
+       enum oldi_mode_reg_val oldi_mode_reg_val;
+       u32 input_bus_fmt;
+};
+
+int tidss_oldi_init(struct tidss_device *tidss);
+void tidss_oldi_deinit(struct tidss_device *tidss);
+
+#endif /* __TIDSS_OLDI_H__ */
-- 
2.34.1

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