On Fri, Jan 16, 2026 at 02:02:47PM +0100, Michael Riesch wrote:

The Synopsys DesignWare MIPI CSI-2 Receiver is a CSI-2 bridge with
one input port and one output port. It receives the data with the
help of an external MIPI PHY (C-PHY or D-PHY) and passes it to e.g.,
the Rockchip Video Capture (VICAP) block on recent Rockchip SoCs.

Add a V4L2 subdevice driver for this unit.

Signed-off-by: Michael Riesch <redacted>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Reviewed-by: Mehdi Djait <mehdi.djait@linux.intel.com>
Signed-off-by: Michael Riesch <michael.riesch@collabora.com>
---

...

+
+static inline struct dw_mipi_csi2_device *to_csi2(struct v4l2_subdev *sd)
+{
+	return container_of(sd, struct dw_mipi_csi2_device, sd);
+}
+
+static inline __maybe_unused void

why need '__maybe_unused', needn't inline. compiler can auto decide and
report unused function if no 'inline'.

+dw_mipi_csi2_write(struct dw_mipi_csi2_device *csi2, unsigned int addr, u32 val)
+{
+	writel(val, csi2->base_addr + addr);
+}
+
+static inline __maybe_unused u32
+dw_mipi_csi2_read(struct dw_mipi_csi2_device *csi2, unsigned int addr)
+{
+	return readl(csi2->base_addr + addr);
+}
+
+static const struct dw_mipi_csi2_format *
+dw_mipi_csi2_find_format(struct dw_mipi_csi2_device *csi2, u32 mbus_code)
+{
+	WARN_ON(csi2->formats_num == 0);
+
+	for (unsigned int i = 0; i < csi2->formats_num; i++) {
+		const struct dw_mipi_csi2_format *format = &csi2->formats[i];
+
+		if (format->code == mbus_code)
+			return format;
+	}
+
+	return NULL;
+}
+
+static int dw_mipi_csi2_start(struct dw_mipi_csi2_device *csi2)
+{
+	struct media_pad *source_pad;
+	union phy_configure_opts opts;
+	s64 link_freq;
+	u32 control = 0;
+	u32 lanes = csi2->lanes_num;
+	int ret;

try keep reverise christmas tree order.

+
+	if (lanes < 1 || lanes > 4)
+		return -EINVAL;
+

...

+
+static int dw_mipi_csi2_register_notifier(struct dw_mipi_csi2_device *csi2)
+{
+	struct v4l2_async_connection *asd;
+	struct v4l2_async_notifier *ntf = &csi2->notifier;
+	struct v4l2_fwnode_endpoint vep;
+	struct v4l2_subdev *sd = &csi2->sd;
+	struct device *dev = csi2->dev;
+	struct fwnode_handle *ep;
+	int ret;
+
+	ep = fwnode_graph_get_endpoint_by_id(dev_fwnode(dev), 0, 0, 0);

use  struct fwnode_handle *ep __free(fwnode_handle) can simplify err
handler.

+	if (!ep)
+		return dev_err_probe(dev, -ENODEV, "failed to get endpoint\n");
+

...

+{
+	struct media_pad *pads = csi2->pads;
+	struct v4l2_subdev *sd = &csi2->sd;
+	int ret;
+
+	ret = dw_mipi_csi2_register_notifier(csi2);
+	if (ret)
+		goto err;
+
+	v4l2_subdev_init(sd, &dw_mipi_csi2_ops);
+	sd->dev = csi2->dev;
+	sd->entity.ops = &dw_mipi_csi2_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 = &dw_mipi_csi2_internal_ops;
+	sd->owner = THIS_MODULE;

I remeber needn't set owner, v4l2_async_register_subdev() do it for you.

+	snprintf(sd->name, sizeof(sd->name), "dw-mipi-csi2 %s",
+		 dev_name(csi2->dev));
+

...

+
+static int dw_mipi_csi2_probe(struct platform_device *pdev)
+{
+	struct device *dev = &pdev->dev;
+	struct dw_mipi_csi2_device *csi2;
+	int ret;
+
+	csi2 = devm_kzalloc(dev, sizeof(*csi2), GFP_KERNEL);
+	if (!csi2)
+		return -ENOMEM;
+	csi2->dev = dev;
+	dev_set_drvdata(dev, csi2);
+
+	csi2->base_addr = devm_platform_ioremap_resource(pdev, 0);
+	if (IS_ERR(csi2->base_addr))
+		return PTR_ERR(csi2->base_addr);
+
+	ret = devm_clk_bulk_get_all(dev, &csi2->clks);
+	if (ret != DW_MIPI_CSI2_CLKS_MAX)
+		return dev_err_probe(dev, -ENODEV, "failed to get clocks\n");
+	csi2->clks_num = ret;
+
+	csi2->phy = devm_phy_get(dev, NULL);
+	if (IS_ERR(csi2->phy))
+		return dev_err_probe(dev, PTR_ERR(csi2->phy),
+				     "failed to get MIPI CSI-2 PHY\n");
+
+	csi2->reset = devm_reset_control_get_exclusive(dev, NULL);
+	if (IS_ERR(csi2->reset))
+		return dev_err_probe(dev, PTR_ERR(csi2->reset),
+				     "failed to get reset\n");
+
+	csi2->formats = formats;
+	csi2->formats_num = ARRAY_SIZE(formats);
+
+	pm_runtime_enable(dev);

devm_pm_runtime_enable() will simple error handle.

+
+	ret = phy_init(csi2->phy);
+	if (ret) {
+		ret = dev_err_probe(dev, ret,
+				    "failed to initialize MIPI CSI-2 PHY\n");
+		goto err_pm_runtime_disable;
+	}
+

...

+
+static int dw_mipi_csi2_runtime_resume(struct device *dev)
+{
+	struct dw_mipi_csi2_device *csi2 = dev_get_drvdata(dev);
+	int ret;
+
+	reset_control_assert(csi2->reset);
+	udelay(5);

Now prefer use fsleep(), which auto choose difference sleep function
according to delay number.

+	reset_control_deassert(csi2->reset);
+
+	ret = clk_bulk_prepare_enable(csi2->clks_num, csi2->clks);
+	if (ret) {
+		dev_err(dev, "failed to enable clocks\n");
+		return ret;
+	}
+
+	return 0;
+}
+
+static DEFINE_RUNTIME_DEV_PM_OPS(dw_mipi_csi2_pm_ops,
+				 dw_mipi_csi2_runtime_suspend,
+				 dw_mipi_csi2_runtime_resume, NULL);
+
+static struct platform_driver dw_mipi_csi2_drv = {
+	.driver = {
+		.name = "dw-mipi-csi2",
+		.of_match_table = dw_mipi_csi2_of_match,
+		.pm = &dw_mipi_csi2_pm_ops,

pm_ptr( &dw_mipi_csi2_pm_ops)

Frank

+	},
+	.probe = dw_mipi_csi2_probe,
+	.remove = dw_mipi_csi2_remove,
+};
+module_platform_driver(dw_mipi_csi2_drv);
+
+MODULE_DESCRIPTION("Synopsys DesignWare MIPI CSI-2 Receiver platform driver");
+MODULE_LICENSE("GPL");

--
2.39.5