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Message-ID: <db2f0c20-ca7e-41c9-be08-67fd1f92c2af@collabora.com>
Date: Mon, 19 Jan 2026 10:49:20 +0100
From: Michael Riesch <michael.riesch@...labora.com>
To: Frank Li <Frank.li@....com>
Cc: Chaoyi Chen <chaoyi.chen@...k-chips.com>,
Kever Yang <kever.yang@...k-chips.com>,
Mehdi Djait <mehdi.djait@...ux.intel.com>,
Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
Laurent Pinchart <laurent.pinchart@...asonboard.com>,
Hans Verkuil <hverkuil@...nel.org>,
Mauro Carvalho Chehab <mchehab@...nel.org>, Rob Herring <robh@...nel.org>,
Krzysztof Kozlowski <krzk+dt@...nel.org>, Conor Dooley
<conor+dt@...nel.org>, Heiko Stuebner <heiko@...ech.de>,
Philipp Zabel <p.zabel@...gutronix.de>,
Sebastian Reichel <sebastian.reichel@...labora.com>,
Nicolas Dufresne <nicolas.dufresne@...labora.com>,
Collabora Kernel Team <kernel@...labora.com>,
Sakari Ailus <sakari.ailus@...ux.intel.com>, linux-media@...r.kernel.org,
devicetree@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 2/3] media: synopsys: add driver for the designware
mipi csi-2 receiver
Hi Frank,
Thanks for your review.
On 1/16/26 17:08, Frank Li wrote:
> 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 <michael.riesch@...fvision.net>
>> Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@...aro.org>
>> Reviewed-by: Mehdi Djait <mehdi.djait@...ux.intel.com>
>> Signed-off-by: Michael Riesch <michael.riesch@...labora.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'.
The __maybe_unused was helpful during development and is not really
required now. It doesn't hurt either, so I left it in. I can remove it
if you wish.
>
>> +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.
Ack.
>
>> +
>> + 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.
Sorry, I don't see the benefit of that.
>
>> + 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.
Indeed, nice catch.
>
>> + 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.
Ack.
>
>> +
>> + 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.
I'll keep that in mind, but here the first thing that fsleep does is to
check whether the parameter is <= 10 and (since this is true) call
udelay. So here I don't see the point really.
>
>> + 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)
Shouldn't make a difference here since this driver depends on CONFIG_PM.
Best regards,
Michael
>
> 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
>>
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