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

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Message-ID: <37c83a9a-088a-4a96-b6f6-343fa6cdddc6@collabora.com>
Date: Mon, 19 Jan 2026 16:40:59 +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,

On 1/19/26 16:35, Frank Li wrote:
> 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

Since Sakari requested this variant as well, I changed it to as you
suggested in v7.

> 
>>>
>>>> +	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().

Interesting. Which tools to you use?

I hope v7 is accepted as sent earlier today, and this should not be a
blocker. We can add pm_ptr() easily in a follow-up patch.

Thanks and regards,
Michael

> 
> 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
>>>>
>>