Hi Sakari,

On 1/14/26 10:34, Sakari Ailus wrote:

Hi Michael,

Thanks for the set.

Thanks for the review :-)

quoted

[...]

diff --git a/drivers/media/platform/rockchip/rkcsi/rkcsi.c b/drivers/media/platform/rockchip/rkcsi/rkcsi.c
new file mode 100644
index 000000000000..03597f03f08f
--- /dev/null
+++ b/drivers/media/platform/rockchip/rkcsi/rkcsi.c

@@ -0,0 +1,742 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Rockchip MIPI CSI-2 Receiver Driver
+ *
+ * Copyright (C) 2019 Rockchip Electronics Co., Ltd.
+ * Copyright (C) 2025 Michael Riesch <michael.riesch@wolfvision.net>
+ * Copyright (C) 2026 Collabora, Ltd.
+ */
+
+#include <linux/clk.h>
+#include <linux/delay.h>
+#include <linux/io.h>
+#include <linux/module.h>
+#include <linux/of.h>
+#include <linux/of_graph.h>
+#include <linux/of_platform.h>

Are the above two needed?

They are not, apparently. I'll remove them.

quoted

+#include <linux/phy/phy.h>
+#include <linux/platform_device.h>
+#include <linux/pm_runtime.h>

#include <linux/property.h>

Ack.

quoted

+#include <linux/reset.h>
[...]
+
+static const struct rkcsi_format *
+rkcsi_find_format(struct rkcsi_device *csi_dev, u32 mbus_code)
+{
+	const struct rkcsi_format *format;

This can be declared within the loop.

Ack.

quoted

+
+	WARN_ON(csi_dev->formats_num == 0);
+
+	for (int i = 0; i < csi_dev->formats_num; i++) {

unsigned int?

Ack.

quoted

+		format = &csi_dev->formats[i];
+		if (format->code == mbus_code)
+			return format;
+	}
+
+	return NULL;
+}
+
+static int rkcsi_start(struct rkcsi_device *csi_dev)
+{
+	struct media_pad *source_pad =
+		&csi_dev->source_sd->entity.pads[csi_dev->source_pad];
+	enum v4l2_mbus_type bus_type = csi_dev->vep.bus_type;
+	union phy_configure_opts opts;
+	s64 link_freq;
+	u32 lanes = csi_dev->vep.bus.mipi_csi2.num_data_lanes;
+	u32 control = 0;
+	int ret;
+
+	if (lanes < 1 || lanes > 4)
+		return -EINVAL;
+
+	/* set mult and div to 0, thus completely rely on V4L2_CID_LINK_FREQ */
+	link_freq = v4l2_get_link_freq(source_pad, 0, 0);
+	if (link_freq <= 0)
+		return -EINVAL;

Could you return link_freq here?

Ack.

quoted

+
+	if (bus_type == V4L2_MBUS_CSI2_DPHY) {
+		struct phy_configure_opts_mipi_dphy *cfg = &opts.mipi_dphy;
+
+		ret = phy_mipi_dphy_get_default_config_for_hsclk(link_freq * 2,
+								 lanes, cfg);
+		if (ret)
+			return ret;
+
+		ret = phy_set_mode(csi_dev->phy, PHY_MODE_MIPI_DPHY);
+		if (ret)
+			return ret;
+
+		ret = phy_configure(csi_dev->phy, &opts);
+		if (ret)
+			return ret;
+
+		control |= SW_CPHY_EN(0);
+
+	} else if (bus_type == V4L2_MBUS_CSI2_CPHY) {
+		/* TODO: implement CPHY configuration */
+		return -EOPNOTSUPP;

How about a switch()?

Ok!

quoted

+	} else {
+		return -EINVAL;
+	}
+
+	control |= SW_DATATYPE_FS(0x00) | SW_DATATYPE_FE(0x01) |
+		   SW_DATATYPE_LS(0x02) | SW_DATATYPE_LE(0x03);
+
+	rkcsi_write(csi_dev, CSI2HOST_N_LANES, lanes - 1);
+	rkcsi_write(csi_dev, CSI2HOST_CONTROL, control);
+	rkcsi_write(csi_dev, CSI2HOST_CSI2_RESETN, 1);
+
+	ret = phy_power_on(csi_dev->phy);

	return ...;

Ack.

quoted

+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static void rkcsi_stop(struct rkcsi_device *csi_dev)
+{
+	phy_power_off(csi_dev->phy);
+
+	rkcsi_write(csi_dev, CSI2HOST_CSI2_RESETN, 0);
+	rkcsi_write(csi_dev, CSI2HOST_MSK1, ~0);
+	rkcsi_write(csi_dev, CSI2HOST_MSK2, ~0);
+}
+
+static const struct media_entity_operations rkcsi_media_ops = {
+	.link_validate = v4l2_subdev_link_validate,
+};
+
+static int rkcsi_enum_mbus_code(struct v4l2_subdev *sd,
+				struct v4l2_subdev_state *sd_state,
+				struct v4l2_subdev_mbus_code_enum *code)
+{
+	struct rkcsi_device *csi_dev = to_rkcsi(sd);
+
+	if (code->pad == RKCSI_PAD_SRC) {
+		const struct v4l2_mbus_framefmt *sink_fmt;
+
+		if (code->index)
+			return -EINVAL;
+
+		sink_fmt = v4l2_subdev_state_get_format(sd_state,
+							RKCSI_PAD_SINK);
+		code->code = sink_fmt->code;
+
+		return 0;
+	} else if (code->pad == RKCSI_PAD_SINK) {

switch() would be nice here.

Ack.

quoted

+		if (code->index > csi_dev->formats_num)
+			return -EINVAL;
+
+		code->code = csi_dev->formats[code->index].code;
+		return 0;
+	}
+
+	return -EINVAL;
+}
+
+static int rkcsi_set_fmt(struct v4l2_subdev *sd,
+			 struct v4l2_subdev_state *state,
+			 struct v4l2_subdev_format *format)
+{
+	struct rkcsi_device *csi_dev = to_rkcsi(sd);
+	const struct rkcsi_format *fmt;
+	struct v4l2_mbus_framefmt *sink, *src;
+
+	/* the format on the source pad always matches the sink pad */
+	if (format->pad == RKCSI_PAD_SRC)
+		return v4l2_subdev_get_fmt(sd, state, format);
+
+	sink = v4l2_subdev_state_get_format(state, format->pad, format->stream);
+	if (!sink)
+		return -EINVAL;
+
+	fmt = rkcsi_find_format(csi_dev, format->format.code);
+	if (!fmt)
+		format->format = default_format;
+
+	*sink = format->format;
+
+	/* propagate the format to the source pad */
+	src = v4l2_subdev_state_get_opposite_stream_format(state, format->pad,
+							   format->stream);
+	if (!src)
+		return -EINVAL;
+
+	*src = *sink;
+
+	return 0;
+}
+
+static int rkcsi_set_routing(struct v4l2_subdev *sd,
+			     struct v4l2_subdev_state *state,
+			     enum v4l2_subdev_format_whence which,
+			     struct v4l2_subdev_krouting *routing)
+{
+	int ret;
+
+	ret = v4l2_subdev_routing_validate(sd, routing,
+					   V4L2_SUBDEV_ROUTING_ONLY_1_TO_1);
+	if (ret)
+		return ret;
+
+	ret = v4l2_subdev_set_routing_with_fmt(sd, state, routing,
+					       &default_format);

	return ...;

Ack.

quoted

+	if (ret)
+		return ret;
+
+	return 0;
+}
+
+static int rkcsi_enable_streams(struct v4l2_subdev *sd,
+				struct v4l2_subdev_state *state, u32 pad,
+				u64 streams_mask)
+{
+	struct rkcsi_device *csi_dev = to_rkcsi(sd);
+	struct v4l2_subdev *remote_sd;
+	struct media_pad *sink_pad, *remote_pad;
+	struct device *dev = csi_dev->dev;
+	u64 mask;
+	int ret;
+
+	sink_pad = &sd->entity.pads[RKCSI_PAD_SINK];
+	remote_pad = media_pad_remote_pad_first(sink_pad);
+	remote_sd = media_entity_to_v4l2_subdev(remote_pad->entity);
+
+	mask = v4l2_subdev_state_xlate_streams(state, RKCSI_PAD_SINK,
+					       RKCSI_PAD_SRC, &streams_mask);
+
+	ret = pm_runtime_resume_and_get(dev);
+	if (ret)
+		goto err;
+
+	ret = rkcsi_start(csi_dev);
+	if (ret) {
+		dev_err(dev, "failed to enable CSI hardware\n");
+		goto err_pm_runtime_put;
+	}
+
+	ret = v4l2_subdev_enable_streams(remote_sd, remote_pad->index, mask);
+	if (ret)
+		goto err_csi_stop;
+
+	return 0;
+
+err_csi_stop:
+	rkcsi_stop(csi_dev);
+err_pm_runtime_put:
+	pm_runtime_put_sync(dev);
+err:
+	return ret;
+}
+
+static int rkcsi_disable_streams(struct v4l2_subdev *sd,
+				 struct v4l2_subdev_state *state, u32 pad,
+				 u64 streams_mask)
+{
+	struct rkcsi_device *csi_dev = to_rkcsi(sd);
+	struct v4l2_subdev *remote_sd;
+	struct media_pad *sink_pad, *remote_pad;
+	struct device *dev = csi_dev->dev;
+	u64 mask;
+	int ret;
+
+	sink_pad = &sd->entity.pads[RKCSI_PAD_SINK];
+	remote_pad = media_pad_remote_pad_first(sink_pad);
+	remote_sd = media_entity_to_v4l2_subdev(remote_pad->entity);
+
+	mask = v4l2_subdev_state_xlate_streams(state, RKCSI_PAD_SINK,
+					       RKCSI_PAD_SRC, &streams_mask);
+
+	ret = v4l2_subdev_disable_streams(remote_sd, remote_pad->index, mask);
+
+	rkcsi_stop(csi_dev);
+
+	pm_runtime_mark_last_busy(dev);

Redundant, please drop.

Ack.

quoted

+	pm_runtime_put_autosuspend(dev);

The driver doesn't enable autosuspend so the autosuspend variant isn't
useful. Maybe just switch to pm_runtime_put(), as resume probably takes
very little time?

Ack.

quoted

+
+	return ret;
+}
+
+static const struct v4l2_subdev_pad_ops rkcsi_pad_ops = {
+	.enum_mbus_code = rkcsi_enum_mbus_code,
+	.get_fmt = v4l2_subdev_get_fmt,
+	.set_fmt = rkcsi_set_fmt,
+	.set_routing = rkcsi_set_routing,
+	.enable_streams = rkcsi_enable_streams,
+	.disable_streams = rkcsi_disable_streams,
+};
+
+static const struct v4l2_subdev_ops rkcsi_ops = {
+	.pad = &rkcsi_pad_ops,
+};
+
+static int rkcsi_init_state(struct v4l2_subdev *sd,
+			    struct v4l2_subdev_state *state)
+{
+	struct v4l2_subdev_route routes[] = {
+		{
+			.sink_pad = RKCSI_PAD_SINK,
+			.sink_stream = 0,
+			.source_pad = RKCSI_PAD_SRC,
+			.source_stream = 0,
+			.flags = V4L2_SUBDEV_ROUTE_FL_ACTIVE,
+		},
+	};
+	struct v4l2_subdev_krouting routing = {
+		.len_routes = ARRAY_SIZE(routes),
+		.num_routes = ARRAY_SIZE(routes),
+		.routes = routes,
+	};
+	int ret;
+
+	ret = v4l2_subdev_set_routing_with_fmt(sd, state, &routing,
+					       &default_format);

	return ...;

Ack.

quoted

+
+	return ret;
+}
+
+static const struct v4l2_subdev_internal_ops rkcsi_internal_ops = {
+	.init_state = rkcsi_init_state,
+};
+
+static int rkcsi_notifier_bound(struct v4l2_async_notifier *notifier,
+				struct v4l2_subdev *sd,
+				struct v4l2_async_connection *asd)
+{
+	struct rkcsi_device *csi_dev =
+		container_of(notifier, struct rkcsi_device, notifier);
+	int source_pad;
+
+	source_pad = media_entity_get_fwnode_pad(&sd->entity, sd->fwnode,
+						 MEDIA_PAD_FL_SOURCE);

Could you use v4l2_create_fwnode_links_to_pad()?

Ack.

quoted

+	if (source_pad < 0) {
+		dev_err(csi_dev->dev, "failed to find source pad for %s\n",
+			sd->name);
+		return source_pad;
+	}
+
+	csi_dev->source_sd = sd;

I'd just use media_pad_remote_pad_unique() to obtain the remote pad when
needed.

Ack.

quoted

+	csi_dev->source_pad = source_pad;
+
+	return media_create_pad_link(&sd->entity, source_pad,
+				     &csi_dev->sd.entity, RKCSI_PAD_SINK,
+				     MEDIA_LNK_FL_ENABLED);
+}
+
+static const struct v4l2_async_notifier_operations rkcsi_notifier_ops = {
+	.bound = rkcsi_notifier_bound,
+};
+
+static int rkcsi_register_notifier(struct rkcsi_device *csi_dev)
+{
+	struct v4l2_async_connection *asd;
+	struct v4l2_async_notifier *ntf = &csi_dev->notifier;
+	struct v4l2_fwnode_endpoint *vep = &csi_dev->vep;
+	struct v4l2_subdev *sd = &csi_dev->sd;
+	struct device *dev = csi_dev->dev;
+	struct fwnode_handle *ep;
+	int ret = 0;

Redundant initialisation.

Ack.

quoted

+
+	ep = fwnode_graph_get_endpoint_by_id(dev_fwnode(dev), 0, 0, 0);
+	if (!ep)
+		return dev_err_probe(dev, -ENODEV, "failed to get endpoint\n");
+
+	vep->bus_type = V4L2_MBUS_UNKNOWN;

If you only need the number of lanes and PHY type, I'd store them to the
driver's own context struct. struct v4l2_fwnode_endpoint isn't tiny.

Ack.

quoted

+	ret = v4l2_fwnode_endpoint_parse(ep, vep);
+	if (ret) {
+		ret = dev_err_probe(dev, ret, "failed to parse endpoint\n");
+		goto out;
+	}
+
+	if (vep->bus_type != V4L2_MBUS_CSI2_DPHY &&
+	    vep->bus_type != V4L2_MBUS_CSI2_CPHY) {
+		ret = dev_err_probe(dev, -EINVAL,
+				    "invalid bus type of endpoint\n");
+		goto out;
+	}
+
+	v4l2_async_subdev_nf_init(ntf, sd);
+	ntf->ops = &rkcsi_notifier_ops;
+
+	asd = v4l2_async_nf_add_fwnode_remote(ntf, ep,
+					      struct v4l2_async_connection);
+	if (IS_ERR(asd)) {
+		ret = PTR_ERR(asd);
+		goto err_nf_cleanup;
+	}
+
+	ret = v4l2_async_nf_register(ntf);
+	if (ret) {
+		ret = dev_err_probe(dev, ret, "failed to register notifier\n");
+		goto err_nf_cleanup;
+	}
+
+	goto out;
+
+err_nf_cleanup:
+	v4l2_async_nf_cleanup(ntf);
+out:
+	fwnode_handle_put(ep);
+	return ret;
+}
+
+static int rkcsi_register(struct rkcsi_device *csi_dev)
+{
+	struct media_pad *pads = csi_dev->pads;
+	struct v4l2_subdev *sd = &csi_dev->sd;
+	int ret;
+
+	ret = rkcsi_register_notifier(csi_dev);
+	if (ret)
+		goto err;
+
+	v4l2_subdev_init(sd, &rkcsi_ops);
+	sd->dev = csi_dev->dev;
+	sd->entity.ops = &rkcsi_media_ops;
+	sd->entity.function = MEDIA_ENT_F_VID_IF_BRIDGE;
+	sd->flags |= V4L2_SUBDEV_FL_HAS_DEVNODE | V4L2_SUBDEV_FL_STREAMS;
+	sd->internal_ops = &rkcsi_internal_ops;
+	sd->owner = THIS_MODULE;
+	snprintf(sd->name, sizeof(sd->name), "rockchip-mipi-csi %s",
+		 dev_name(csi_dev->dev));

Do you need to give it an explicit name? (v4l2_i2c_subdev_init() already
does that.)

I do, actually. I don't call the _i2c_ variant. This is a platform device.

quoted

+
+	pads[RKCSI_PAD_SINK].flags = MEDIA_PAD_FL_SINK |
+				     MEDIA_PAD_FL_MUST_CONNECT;
+	pads[RKCSI_PAD_SRC].flags = MEDIA_PAD_FL_SOURCE;
+	ret = media_entity_pads_init(&sd->entity, RKCSI_PAD_MAX, pads);
+	if (ret)
+		goto err_notifier_unregister;
+
+	ret = v4l2_subdev_init_finalize(sd);
+	if (ret)
+		goto err_entity_cleanup;
+
+	ret = v4l2_async_register_subdev(sd);
+	if (ret) {
+		dev_err(sd->dev, "failed to register CSI subdev\n");
+		goto err_subdev_cleanup;
+	}
+
+	return 0;
+
+err_subdev_cleanup:
+	v4l2_subdev_cleanup(sd);
+err_entity_cleanup:
+	media_entity_cleanup(&sd->entity);
+err_notifier_unregister:
+	v4l2_async_nf_unregister(&csi_dev->notifier);
+	v4l2_async_nf_cleanup(&csi_dev->notifier);
+err:
+	return ret;
+}
+
+static void rkcsi_unregister(struct rkcsi_device *csi_dev)
+{
+	struct v4l2_subdev *sd = &csi_dev->sd;
+
+	v4l2_async_unregister_subdev(sd);
+	v4l2_subdev_cleanup(sd);
+	media_entity_cleanup(&sd->entity);
+	v4l2_async_nf_unregister(&csi_dev->notifier);
+	v4l2_async_nf_cleanup(&csi_dev->notifier);
+}
+
+static const struct of_device_id rkcsi_of_match[] = {
+	{
+		.compatible = "rockchip,rk3568-mipi-csi",
+	},
+	{}
+};
+MODULE_DEVICE_TABLE(of, rkcsi_of_match);
+
+static int rkcsi_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct rkcsi_device *csi_dev;
+	int ret;
+
+	csi_dev = devm_kzalloc(dev, sizeof(*csi_dev), GFP_KERNEL);
+	if (!csi_dev)
+		return -ENOMEM;
+	csi_dev->dev = dev;
+	dev_set_drvdata(dev, csi_dev);
+
+	csi_dev->base_addr = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(csi_dev->base_addr))
+		return PTR_ERR(csi_dev->base_addr);
+
+	ret = devm_clk_bulk_get_all(dev, &csi_dev->clks);
+	if (ret != RKCSI_CLKS_MAX)
+		return dev_err_probe(dev, -ENODEV, "failed to get clocks\n");
+	csi_dev->clks_num = ret;
+
+	csi_dev->phy = devm_phy_get(dev, NULL);
+	if (IS_ERR(csi_dev->phy))
+		return dev_err_probe(dev, PTR_ERR(csi_dev->phy),
+				     "failed to get MIPI CSI PHY\n");
+
+	csi_dev->reset = devm_reset_control_get_exclusive(dev, NULL);
+	if (IS_ERR(csi_dev->reset))
+		return dev_err_probe(dev, PTR_ERR(csi_dev->reset),
+				     "failed to get reset\n");
+
+	csi_dev->formats = formats;
+	csi_dev->formats_num = ARRAY_SIZE(formats);
+
+	pm_runtime_enable(dev);

You're not resuming the device in probe(). I guess you depend on CONFIG_PM?

I do depend on CONFIG_PM.

I don't think there is need to resume in probe -> resume in
_enable_streams should do the trick, right?

quoted

+
+	ret = phy_init(csi_dev->phy);
+	if (ret) {
+		ret = dev_err_probe(dev, ret,
+				    "failed to initialize MIPI CSI PHY\n");
+		goto err_pm_runtime_disable;
+	}
+
+	ret = rkcsi_register(csi_dev);
+	if (ret)
+		goto err_phy_exit;
+
+	return 0;
+
+err_phy_exit:
+	phy_exit(csi_dev->phy);
+err_pm_runtime_disable:
+	pm_runtime_disable(dev);

A newline would be nice here.

Ack.

quoted

+	return ret;
+}
+
+static void rkcsi_remove(struct platform_device *pdev)
+{
+	struct rkcsi_device *csi_dev = platform_get_drvdata(pdev);
+	struct device *dev = &pdev->dev;
+
+	rkcsi_unregister(csi_dev);
+	phy_exit(csi_dev->phy);
+	pm_runtime_disable(dev);
+}
+
+static int rkcsi_runtime_suspend(struct device *dev)
+{
+	struct rkcsi_device *csi_dev = dev_get_drvdata(dev);
+
+	clk_bulk_disable_unprepare(csi_dev->clks_num, csi_dev->clks);
+
+	return 0;
+}
+
+static int rkcsi_runtime_resume(struct device *dev)
+{
+	struct rkcsi_device *csi_dev = dev_get_drvdata(dev);
+	int ret;
+
+	reset_control_assert(csi_dev->reset);
+	udelay(5);
+	reset_control_deassert(csi_dev->reset);
+
+	ret = clk_bulk_prepare_enable(csi_dev->clks_num, csi_dev->clks);
+	if (ret) {
+		dev_err(dev, "failed to enable clocks\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static const struct dev_pm_ops rkcsi_pm_ops = {
+	.runtime_suspend = rkcsi_runtime_suspend,
+	.runtime_resume = rkcsi_runtime_resume,
+};

Could you use DEFINE_RUNTIME_DEV_PM_OPS() (add static in front)?

Ack.

v4 coming up soon!

Best regards,
Michael

quoted

+
+static struct platform_driver rkcsi_drv = {
+	.driver = {
+		   .name = "rockchip-mipi-csi",
+		   .of_match_table = rkcsi_of_match,
+		   .pm = &rkcsi_pm_ops,
+	},
+	.probe = rkcsi_probe,
+	.remove = rkcsi_remove,
+};
+module_platform_driver(rkcsi_drv);
+
+MODULE_DESCRIPTION("Rockchip MIPI CSI-2 Receiver platform driver");
+MODULE_LICENSE("GPL");