drm/imx: add internal bridge handling display-timings DT node

i.MX DRM DT bindings allow using either a proper panel / bridge graph to
provide information about connected panels, or just a display-timings DT
node, describing just the timings and the flags. Add helper bridge
driver supporting the latter usecase. It will be used by both LDB and
parallel-display drivers.

Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Tested-by: Chris Healy <cphealy@gmail.com>
Tested-by: Philipp Zabel <p.zabel@pengutronix.de> # on imx6q-nitrogen6x
Link: https://patchwork.freedesktop.org/patch/msgid/20240602-drm-imx-cleanup-v3-9-e549e2a43100@linaro.org
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>

drivers/gpu/drm/bridge/imx/Kconfig

@@ -3,6 +3,16 @@ if ARCH_MXC || COMPILE_TEST
 config DRM_IMX_LDB_HELPER
 	tristate
 
+config DRM_IMX_LEGACY_BRIDGE
+	tristate
+	depends on DRM_IMX
+	help
+	  This is a DRM bridge implementation for the DRM i.MX IPUv3 driver,
+	  that uses of_get_drm_display_mode to acquire display mode.
+
+	  Newer designs should not use this bridge and should use proper panel
+	  driver instead.
+
 config DRM_IMX8MP_DW_HDMI_BRIDGE
 	tristate "Freescale i.MX8MP HDMI-TX bridge support"
 	depends on OF

drivers/gpu/drm/bridge/imx/Makefile

@@ -1,4 +1,5 @@
 obj-$(CONFIG_DRM_IMX_LDB_HELPER) += imx-ldb-helper.o
+obj-$(CONFIG_DRM_IMX_LEGACY_BRIDGE) += imx-legacy-bridge.o
 obj-$(CONFIG_DRM_IMX8MP_DW_HDMI_BRIDGE) += imx8mp-hdmi-tx.o
 obj-$(CONFIG_DRM_IMX8MP_HDMI_PVI) += imx8mp-hdmi-pvi.o
 obj-$(CONFIG_DRM_IMX8QM_LDB) += imx8qm-ldb.o

drivers/gpu/drm/bridge/imx/imx-legacy-bridge.c

@@ -0,0 +1,87 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Freescale i.MX drm driver
+ *
+ * bridge driver for legacy DT bindings, utilizing display-timings node
+ */
+
+#include <drm/drm_bridge.h>
+#include <drm/drm_modes.h>
+#include <drm/drm_probe_helper.h>
+#include <drm/bridge/imx.h>
+
+#include <video/of_display_timing.h>
+#include <video/of_videomode.h>
+
+struct imx_legacy_bridge {
+	struct drm_bridge base;
+
+	struct drm_display_mode mode;
+	u32 bus_flags;
+};
+
+#define to_imx_legacy_bridge(bridge)	container_of(bridge, struct imx_legacy_bridge, base)
+
+static int imx_legacy_bridge_attach(struct drm_bridge *bridge,
+				   enum drm_bridge_attach_flags flags)
+{
+	if (!(flags & DRM_BRIDGE_ATTACH_NO_CONNECTOR))
+		return -EINVAL;
+
+	return 0;
+}
+
+static int imx_legacy_bridge_get_modes(struct drm_bridge *bridge,
+				       struct drm_connector *connector)
+{
+	struct imx_legacy_bridge *imx_bridge = to_imx_legacy_bridge(bridge);
+	int ret;
+
+	ret = drm_connector_helper_get_modes_fixed(connector, &imx_bridge->mode);
+	if (ret)
+		return ret;
+
+	connector->display_info.bus_flags = imx_bridge->bus_flags;
+
+	return 0;
+}
+
+struct drm_bridge_funcs imx_legacy_bridge_funcs = {
+	.attach = imx_legacy_bridge_attach,
+	.get_modes = imx_legacy_bridge_get_modes,
+};
+
+struct drm_bridge *devm_imx_drm_legacy_bridge(struct device *dev,
+					      struct device_node *np,
+					      int type)
+{
+	struct imx_legacy_bridge *imx_bridge;
+	int ret;
+
+	imx_bridge = devm_kzalloc(dev, sizeof(*imx_bridge), GFP_KERNEL);
+	if (!imx_bridge)
+		return ERR_PTR(-ENOMEM);
+
+	ret = of_get_drm_display_mode(np,
+				      &imx_bridge->mode,
+				      &imx_bridge->bus_flags,
+				      OF_USE_NATIVE_MODE);
+	if (ret)
+		return ERR_PTR(ret);
+
+	imx_bridge->mode.type |= DRM_MODE_TYPE_DRIVER;
+
+	imx_bridge->base.funcs = &imx_legacy_bridge_funcs;
+	imx_bridge->base.of_node = np;
+	imx_bridge->base.ops = DRM_BRIDGE_OP_MODES;
+	imx_bridge->base.type = type;
+
+       ret = devm_drm_bridge_add(dev, &imx_bridge->base);
+       if (ret)
+               return ERR_PTR(ret);
+
+	return &imx_bridge->base;
+}
+EXPORT_SYMBOL_GPL(devm_imx_drm_legacy_bridge);
+
+MODULE_LICENSE("GPL");

include/drm/bridge/imx.h

@@ -0,0 +1,13 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2012 Sascha Hauer, Pengutronix
+ */
+
+#ifndef DRM_IMX_BRIDGE_H
+#define DRM_IMX_BRIDGE_H
+
+struct drm_bridge *devm_imx_drm_legacy_bridge(struct device *dev,
+					      struct device_node *np,
+					      int type);
+
+#endif