Date: Sun, 12 May 2024 01:00:55 +0530
From: Aradhya Bhatia <a-bhatia1@...com>
To: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>,
        Jyri Sarha
	<jyri.sarha@....fi>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Laurent Pinchart
	<Laurent.pinchart@...asonboard.com>,
        David Airlie <airlied@...il.com>, Daniel
 Vetter <daniel@...ll.ch>,
        Rob Herring <robh@...nel.org>,
        Krzysztof Kozlowski
	<krzk+dt@...nel.org>,
        Conor Dooley <conor+dt@...nel.org>
CC: DRI Development List <dri-devel@...ts.freedesktop.org>,
        Devicetree List
	<devicetree@...r.kernel.org>,
        Linux Kernel List
	<linux-kernel@...r.kernel.org>,
        Nishanth Menon <nm@...com>, Vignesh
 Raghavendra <vigneshr@...com>,
        Praneeth Bajjuri <praneeth@...com>, Udit Kumar
	<u-kumar1@...com>,
        Francesco Dolcini <francesco@...cini.it>,
        Alexander
 Sverdlin <alexander.sverdlin@...mens.com>,
        Randolph Sapp <rs@...com>, Devarsh
 Thakkar <devarsht@...com>,
        Jayesh Choudhary <j-choudhary@...com>, Jai Luthra
	<j-luthra@...com>,
        Aradhya Bhatia <a-bhatia1@...com>
Subject: [PATCH 4/4] drm/tidss: Add OLDI bridge support

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-bhatia1@...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-bhatia1@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-bhati1@...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-bhati1@...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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