linux-kernel - Re: [PATCH v5 2/3] media: synopsys: add driver for the designware mipi csi-2 receiver

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Message-ID: <aW5PLIv2w+OY7xJD@lizhi-Precision-Tower-5810>
Date: Mon, 19 Jan 2026 10:35:08 -0500
From: Frank Li <Frank.li@....com>
To: Michael Riesch <michael.riesch@...labora.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

On Mon, Jan 19, 2026 at 10:49:20AM +0100, Michael Riesch wrote:
> 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.
>
> >
> >> +
> >> +	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.
>

I remember reduce one goto

> >
> >> +	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;
> >> +
> >> +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.

Thank.

>
> >
> >> +	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.
>

Avoid some static scan tools to report the problem, no harmful to add
pm_ptr().

Frank

> 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
> >>
>