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Date:   Tue, 17 Nov 2020 12:59:02 +0100
From:   Jacopo Mondi <jacopo@jmondi.org>
To:     Eugen Hristev <eugen.hristev@microchip.com>
Cc:     linux-kernel@vger.kernel.org, linux-media@vger.kernel.org,
        devicetree@vger.kernel.org, robh+dt@kernel.org,
        sakari.ailus@iki.fi, laurent.pinchart@ideasonboard.com
Subject: Re: [PATCH v5 2/3] media: atmel: introduce microchip csi2dc driver
Message-ID: <20201117115902.unnrnccoj3s4gtam@uno.localdomain>
References: <20201112133437.372475-1-eugen.hristev@microchip.com>
 <20201112133437.372475-2-eugen.hristev@microchip.com>
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In-Reply-To: <20201112133437.372475-2-eugen.hristev@microchip.com>
Precedence: bulk

Hi Eugen,

On Thu, Nov 12, 2020 at 03:34:36PM +0200, Eugen Hristev wrote:
> Microchip CSI2DC (CSI2 Demultiplexer Controller) is a misc bridge device
> that converts a byte stream in IDI Synopsys format (coming from a CSI2HOST)
> to a pixel stream that can be captured by a sensor controller.
>
> Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
> ---
> Hello,
>
> There still are some open questions regarding the last reviews on the ML.
>
> Regarding the format list which is not const, I cannot have it const because
> I reference elements from this list into a dynamic list which is non-const.
>
> Regarding the presence of the v4l2_dev, without this I cannot add a notifier
> for this device to have it async completed , when the underlying subdevice
> finishes probing.
>

I see you have a discussion with Sakari on-going on this, and I have
the very same comment he had.

Should a sub-notifier be used and this driver should not register any
v4l2_dev but integrate in the media graph of the receiver ?

For reference, rcar-csi2 uses sub-notifiers and register in the
rcar-vin media graph, it doesn't need to set up a v4l2_dev.

rcar-vin (the DMA engine driver) that register video nodes and the v4l2-dev
also registers the device nodes for all the connected subdevices.

> Regarding the callbacks for set frame interval, set frame size, etc, I cannot
> remove them because losing functionality to the underlying subdevice, as
> explained in :
> https://lkml.org/lkml/2020/10/12/427
>

Using the frame sizes as in the example you reported, if this device has
limitations on the supported sizes, (a min and a max most
probably) that's the only thing that should be exposed from this
driver subdevice. The sensor subdevice instead will report the
available discrete sizes and userspace configures the sensor's source
pad and the bridge's sink pad with the same sizes to properly set up the
capture pipeline. video0 should not report the sizes exposed by the sensor
nor any information that depends on what's connected to it.

I know what your next question is: what about existing application
that only know about video0 and want to setup everything from there. I
understand vendors not wanting to wrap gstreamer or what is used in
the wild in custom scripts that sets up the pipeline opportunely
before streaming, and I'm pretty sure you know what is the solution I
would propose for this :)

I've just gone through the same path with RPi's Unicam, that does the
same thing as your one does: it's an MC driver, but wants to control
the sensor through the v4l2-subdev kAPI to support legacy use cases
not covered by libcamera. The fact is that we're stuck in this limbo
where MC pipeline tries to decouple components one from each other and
delegate their configuration to userspace, but at the same time
vendors want to be able to use the simple plain video node centric
interface because of their existing user base, so I understand your
discomfort, but the 'simple plain' approach is what's preventing Linux
platforms to be in-par with proprietary and custom solutions for any
use case that is not a simple frame capture, so I think it's fair for
mainline to push for this evolution to happen. Just my2c of course.

Some more comments on the implementation below

> Changes in v5:
> - only in bindings
>
> Changes in v4:
> - now using get_mbus_config ops to get data from the subdevice, like the
> virtual channel id, and the clock type.
> - now having possibility to select any of the RAW10 data modes
> - at completion time, select which formats are also available in the subdevice,
> and move to the dynamic list accordingly
> - changed the pipeline integration, do not advertise subdev ready at probe time.
> wait until completion is done, and then start a workqueue that will register
> this device as a subdevice for the next element in pipeline.
> - moved the s_power code into a different function called now csi2dc_power
> that is called with CONFIG_PM functions. This is also called at completion,
> to have the device ready in case CONFIG_PM is not selected on the platform.
> - merged try_fmt into set_fmt
> - driver cleanup, wrapped lines over 80 characters
>
> Changes in v2:
> - moved driver to platform/atmel
> - fixed minor things as per Sakari's review
> - still some things from v2 review are not yet addressed, to be followed up
>
>  drivers/media/platform/atmel/Kconfig          |  13 +
>  drivers/media/platform/atmel/Makefile         |   1 +
>  .../media/platform/atmel/microchip-csi2dc.c   | 785 ++++++++++++++++++
>  3 files changed, 799 insertions(+)
>  create mode 100644 drivers/media/platform/atmel/microchip-csi2dc.c
>
> diff --git a/drivers/media/platform/atmel/Kconfig b/drivers/media/platform/atmel/Kconfig
> index 99b51213f871..147e1c14129b 100644
> --- a/drivers/media/platform/atmel/Kconfig
> +++ b/drivers/media/platform/atmel/Kconfig
> @@ -32,3 +32,16 @@ config VIDEO_ATMEL_ISI
>  	help
>  	  This module makes the ATMEL Image Sensor Interface available
>  	  as a v4l2 device.
> +
> +config VIDEO_MICROCHIP_CSI2DC
> +	tristate "Microchip CSI2 Demux Controller"
> +	depends on VIDEO_V4L2 && COMMON_CLK && OF
> +	depends on ARCH_AT91 || COMPILE_TEST
> +	select MEDIA_CONTROLLER
> +	select VIDEO_V4L2_SUBDEV_API
> +	select V4L2_FWNODE
> +	help
> +	  CSI2 Demux Controller driver. CSI2DC is a helper chip
> +	  that converts IDI interface byte stream to a parallel pixel stream.
> +	  It supports various RAW formats as input.
> +	  Performs clock domain crossing between hardware blocks.

Is the last phrase necessary ? Also missing the usual

	  To compile this driver as a module, choose M here: the
	  module will be called ...

> diff --git a/drivers/media/platform/atmel/Makefile b/drivers/media/platform/atmel/Makefile
> index c5c01556c653..8e80af500bf5 100644
> --- a/drivers/media/platform/atmel/Makefile
> +++ b/drivers/media/platform/atmel/Makefile
> @@ -5,3 +5,4 @@ atmel-xisc-objs = atmel-sama7g5-isc.o atmel-isc-base.o
>  obj-$(CONFIG_VIDEO_ATMEL_ISI) += atmel-isi.o
>  obj-$(CONFIG_VIDEO_ATMEL_ISC) += atmel-isc.o
>  obj-$(CONFIG_VIDEO_ATMEL_XISC) += atmel-xisc.o
> +obj-$(CONFIG_VIDEO_MICROCHIP_CSI2DC) += microchip-csi2dc.o
> diff --git a/drivers/media/platform/atmel/microchip-csi2dc.c b/drivers/media/platform/atmel/microchip-csi2dc.c
> new file mode 100644
> index 000000000000..fda1d5882dbb
> --- /dev/null
> +++ b/drivers/media/platform/atmel/microchip-csi2dc.c
> @@ -0,0 +1,785 @@
> +// SPDX-License-Identifier: GPL-2.0

Nit: I see GPL-2.0 listed as deprecated by spdx.org
Should you use one of:
        	GPL-2.0-only
               	GPL-2.0-or-later

> +/*
> + * Microchip CSI2 Demux Controller (CSI2DC) driver
> + *
> + * Copyright (C) 2018-2020 Microchip Technology, Inc.
> + *
> + * Author: Eugen Hristev <eugen.hristev@microchip.com>
> + *
> + */
> +
> +#include <linux/clk.h>
> +#include <linux/module.h>
> +#include <linux/of.h>
> +#include <linux/of_graph.h>
> +#include <linux/platform_device.h>
> +#include <linux/pm_runtime.h>
> +#include <linux/videodev2.h>
> +
> +#include <media/v4l2-device.h>
> +#include <media/v4l2-fwnode.h>
> +#include <media/v4l2-subdev.h>
> +#include <media/videobuf2-dma-contig.h>
> +
> +/* Global configuration register */
> +#define CSI2DC_GCFG			0x0
> +
> +/* MIPI sensor pixel clock is free running */
> +#define CSI2DC_GCFG_MIPIFRN		BIT(0)
> +/* Output waveform inter-line minimum delay */
> +#define CSI2DC_GCFG_HLC(v)		((v) << 4)
> +#define CSI2DC_GCFG_HLC_MASK		GENMASK(7, 4)
> +/* SAMA7G5 requires a HLC delay of 15 */
> +#define SAMA7G5_HLC			(15)
> +
> +/* Global control register */
> +#define CSI2DC_GCTLR			0x04
> +#define CSI2DC_GCTLR_SWRST		BIT(0)
> +
> +/* Global status register */
> +#define CSI2DC_GS			0x08
> +
> +/* SSP interrupt status register */
> +#define CSI2DC_SSPIS			0x28
> +/* Pipe update register */
> +#define CSI2DC_PU			0xC0
> +/* Video pipe attributes update */
> +#define CSI2DC_PU_VP			BIT(0)
> +
> +/* Pipe update status register */
> +#define CSI2DC_PUS			0xC4
> +
> +/* Video pipeline enable register */
> +#define CSI2DC_VPE			0xF8
> +#define CSI2DC_VPE_ENABLE		BIT(0)
> +
> +/* Video pipeline configuration register */
> +#define CSI2DC_VPCFG			0xFC
> +/* Data type */
> +#define CSI2DC_VPCFG_DT(v)		((v) << 0)
> +#define CSI2DC_VPCFG_DT_MASK		GENMASK(5, 0)
> +/* Virtual channel identifier */
> +#define CSI2DC_VPCFG_VC(v)		((v) << 6)
> +#define CSI2DC_VPCFG_VC_MASK		GENMASK(7, 6)
> +/* Decompression enable */
> +#define CSI2DC_VPCFG_DE			BIT(8)
> +/* Decoder mode */
> +#define CSI2DC_VPCFG_DM(v)		((v) << 9)
> +#define CSI2DC_VPCFG_DM_DECODER8TO12	0
> +/* Decoder predictor 2 selection */
> +#define CSI2DC_VPCFG_DP2		BIT(12)
> +/* Recommended memory storage */
> +#define CSI2DC_VPCFG_RMS		BIT(13)
> +/* Post adjustment */
> +#define CSI2DC_VPCFG_PA			BIT(14)
> +
> +/* Video pipeline column register */
> +#define CSI2DC_VPCOL			0x100
> +/* Column number */
> +#define CSI2DC_VPCOL_COL(v)		((v) << 0)
> +#define CSI2DC_VPCOL_COL_MASK		GENMASK(15, 0)
> +
> +/* Video pipeline row register */
> +#define CSI2DC_VPROW			0x104
> +/* Row number */
> +#define CSI2DC_VPROW_ROW(v)		((v) << 0)
> +#define CSI2DC_VPROW_ROW_MASK		GENMASK(15, 0)
> +
> +/* Version register */
> +#define CSI2DC_VERSION			0x1FC
> +
> +/* register read/write helpers */
> +#define csi2dc_readl(st, reg)		readl_relaxed((st)->base + (reg))
> +#define csi2dc_writel(st, reg, val)	writel_relaxed((val), \
> +					(st)->base + (reg))
> +
> +/* supported RAW data types */
> +#define CSI2DC_DT_RAW6			0x28
> +#define CSI2DC_DT_RAW7			0x29
> +#define CSI2DC_DT_RAW8			0x2A
> +#define CSI2DC_DT_RAW10			0x2B
> +#define CSI2DC_DT_RAW12			0x2C
> +#define CSI2DC_DT_RAW14			0x2D
> +
> +struct csi2dc_format {
> +	u32				mbus_code;
> +	u32				dt;
> +};
> +
> +static struct csi2dc_format csi2dc_formats_list[] = {
> +	{
> +		.mbus_code =		MEDIA_BUS_FMT_SRGGB10_1X10,
> +		.dt =			CSI2DC_DT_RAW10,
> +	}, {
> +		.mbus_code =		MEDIA_BUS_FMT_SBGGR10_1X10,
> +		.dt =			CSI2DC_DT_RAW10,
> +	}, {
> +		.mbus_code =		MEDIA_BUS_FMT_SGRBG10_1X10,
> +		.dt =			CSI2DC_DT_RAW10,
> +	}, {
> +		.mbus_code =		MEDIA_BUS_FMT_SGBRG10_1X10,
> +		.dt =			CSI2DC_DT_RAW10,
> +	},
> +};
> +
> +enum mipi_csi_pads {
> +	CSI2DC_PAD_SINK			= 0,
> +	CSI2DC_PAD_SOURCE		= 1,
> +	CSI2DC_PADS_NUM			= 2,
> +};
> +
> +struct csi2dc_device {
> +	void __iomem			*base;
> +	struct v4l2_subdev		csi2dc_sd;
> +	struct device			*dev;
> +	struct v4l2_device		v4l2_dev;
> +	struct clk			*pclk;
> +	struct clk			*scck;
> +
> +	bool				video_pipe;
> +
> +	u32				num_fmts;
> +	struct csi2dc_format		**formats;
> +
> +	struct csi2dc_format		*cur_fmt;
> +	struct csi2dc_format		*try_fmt;
> +
> +	struct media_pad		pads[CSI2DC_PADS_NUM];
> +
> +	bool				clk_gated;
> +	u32				vc;
> +
> +	struct v4l2_async_subdev	*asd;
> +	struct v4l2_async_notifier	notifier;
> +
> +	struct v4l2_subdev		*input_sd;
> +
> +	u32				remote_pad;
> +
> +	bool				completed;
> +	bool				powered_on;
> +
> +	struct work_struct		workq;
> +};
> +
> +static void csi2dc_vp_update(struct csi2dc_device *csi2dc)
> +{
> +	u32 vp;
> +
> +	vp = CSI2DC_VPCFG_DT(csi2dc->cur_fmt->dt) & CSI2DC_VPCFG_DT_MASK;
> +	vp |= CSI2DC_VPCFG_VC(csi2dc->vc) & CSI2DC_VPCFG_VC_MASK;
> +	vp &= ~CSI2DC_VPCFG_DE;
> +	vp |= CSI2DC_VPCFG_DM(CSI2DC_VPCFG_DM_DECODER8TO12);
> +	vp &= ~CSI2DC_VPCFG_DP2;
> +	vp &= ~CSI2DC_VPCFG_RMS;
> +	vp |= CSI2DC_VPCFG_PA;
> +
> +	csi2dc_writel(csi2dc, CSI2DC_VPCFG, vp);
> +	csi2dc_writel(csi2dc, CSI2DC_VPE, CSI2DC_VPE_ENABLE);
> +	csi2dc_writel(csi2dc, CSI2DC_PU, CSI2DC_PU_VP);
> +}
> +
> +static inline struct csi2dc_device *
> +csi2dc_sd_to_csi2dc_device(struct v4l2_subdev *csi2dc_sd)
> +{
> +	return container_of(csi2dc_sd, struct csi2dc_device, csi2dc_sd);
> +}
> +
> +static int csi2dc_enum_mbus_code(struct v4l2_subdev *csi2dc_sd,
> +				 struct v4l2_subdev_pad_config *cfg,
> +				 struct v4l2_subdev_mbus_code_enum *code)
> +{
> +	struct csi2dc_device *csi2dc = csi2dc_sd_to_csi2dc_device(csi2dc_sd);
> +
> +	if (code->index >= csi2dc->num_fmts)
> +		return -EINVAL;
> +
> +	code->code = csi2dc->formats[code->index]->mbus_code;
> +	return 0;
> +}
> +
> +static int csi2dc_set_fmt(struct v4l2_subdev *csi2dc_sd,
> +			  struct v4l2_subdev_pad_config *cfg,
> +			  struct v4l2_subdev_format *req_fmt)
> +{
> +	struct csi2dc_device *csi2dc = csi2dc_sd_to_csi2dc_device(csi2dc_sd);
> +	struct csi2dc_format *fmt;
> +	int ret, i;
> +
> +	if (!csi2dc->completed) {
> +		dev_dbg((csi2dc)->dev, "subdev not registered yet\n");
> +		return 0;
> +	}
> +
> +	for (fmt = csi2dc->formats[0], i = 0; i < csi2dc->num_fmts; fmt++, i++)
> +		if (req_fmt->format.code == fmt->mbus_code)
> +			csi2dc->try_fmt = fmt;
> +
> +	/* in case we could not find the desired format, default to something */
> +	if (!csi2dc->try_fmt  ||
> +	    req_fmt->format.code != csi2dc->try_fmt->mbus_code) {
> +		csi2dc->try_fmt = csi2dc->formats[0];
> +
> +		dev_dbg(csi2dc->dev,
> +			"CSI2DC unsupported format 0x%x, defaulting to 0x%x\n",
> +			req_fmt->format.code, csi2dc->formats[0]->mbus_code);
> +
> +		req_fmt->format.code = csi2dc->formats[0]->mbus_code;
> +	}
> +
> +	/* if we are just trying, we are done */
> +	if (req_fmt->which == V4L2_SUBDEV_FORMAT_TRY)
> +		return 0;
> +
> +	ret = v4l2_subdev_call(csi2dc->input_sd, pad, set_fmt, cfg, req_fmt);
> +	if (ret) {
> +		dev_err(csi2dc->dev, "input subdev failed %d\n", ret);
> +		return ret;
> +	}
> +
> +	csi2dc->cur_fmt = csi2dc->try_fmt;
> +	/* update video pipe */
> +	csi2dc_vp_update(csi2dc);
> +
> +	dev_dbg(csi2dc->dev, "CSI2DC new format: 0x%x\n", req_fmt->format.code);
> +	return 0;
> +}
> +
> +static int csi2dc_formats_init(struct csi2dc_device *csi2dc)
> +{
> +	struct csi2dc_format *fmt;
> +	struct v4l2_subdev *subdev = csi2dc->input_sd;
> +	unsigned int num_fmts, i;
> +
> +	struct v4l2_subdev_mbus_code_enum mbus_code = {
> +		.which = V4L2_SUBDEV_FORMAT_ACTIVE,
> +		.index = 0,
> +	};
> +
> +	num_fmts = 0;
> +
> +	csi2dc->formats = devm_kcalloc(csi2dc->dev,
> +				       ARRAY_SIZE(csi2dc_formats_list),
> +				       sizeof(*csi2dc->formats), GFP_KERNEL);
> +	if (!csi2dc->formats)
> +		return -ENOMEM;
> +
> +	while (!v4l2_subdev_call(subdev, pad, enum_mbus_code, NULL,
> +	       &mbus_code)) {
> +		mbus_code.index++;
> +		for (fmt = &csi2dc_formats_list[0], i = 0;
> +		     i < ARRAY_SIZE(csi2dc_formats_list); i++, fmt++)
> +			if (fmt->mbus_code == mbus_code.code) {
> +				csi2dc->formats[num_fmts] = fmt;
> +				num_fmts++;
> +			}
> +	}

For the reasons explained above and by Sakari, I think this should be dropped

> +
> +	if (!num_fmts)
> +		return -ENXIO;
> +
> +	csi2dc->num_fmts = num_fmts;
> +
> +	return 0;
> +}
> +
> +static int csi2dc_power(struct csi2dc_device *csi2dc, int on)
> +{
> +	int ret = 0;
> +
> +	if (!csi2dc->completed) {
> +		dev_dbg((csi2dc)->dev, "subdev not registered yet\n");
> +		return 0;
> +	}

Can this happen ?

> +
> +	if (csi2dc->powered_on == on)
> +		return 0;

Same question

> +
> +	if (on)
> +		ret = clk_prepare_enable(csi2dc->scck);
> +	else
> +		clk_disable_unprepare(csi2dc->scck);
> +	if (ret)
> +		dev_err(csi2dc->dev, "failed to enable scck: %d\n", ret);
> +
> +	/* if powering up, deassert reset line */
> +	if (on)
> +		csi2dc_writel(csi2dc, CSI2DC_GCTLR, CSI2DC_GCTLR_SWRST);
> +
> +	/* if powering down, assert reset line */
> +	if (!on)
> +		csi2dc_writel(csi2dc, CSI2DC_GCTLR, !CSI2DC_GCTLR_SWRST);
> +	if (!ret)
> +		csi2dc->powered_on = on;

Wouldn't this be better coded as

        if (on) {
                clk_prepare_enable
                csi2dc_writel(SWRST)
                powered_on = true
        } else {
                clk_disable_unrepare
                csi2dc_writel(!SWRST)
                powered_on = false
        }
> +
> +	return ret;
> +}
> +
> +static int csi2dc_s_stream(struct v4l2_subdev *csi2dc_sd, int enable)
> +{
> +	struct csi2dc_device *csi2dc = csi2dc_sd_to_csi2dc_device(csi2dc_sd);
> +
> +	if (!csi2dc->completed) {
> +		dev_dbg((csi2dc)->dev, "subdev not registered yet\n");
> +		return 0;
> +	}
> +
> +	return v4l2_subdev_call(csi2dc->input_sd, video, s_stream, enable);
> +}
> +
> +static int csi2dc_g_frame_interval(struct v4l2_subdev *csi2dc_sd,
> +				   struct v4l2_subdev_frame_interval *interval)
> +{
> +	struct csi2dc_device *csi2dc = csi2dc_sd_to_csi2dc_device(csi2dc_sd);
> +
> +	if (!csi2dc->completed) {
> +		dev_dbg((csi2dc)->dev, "subdev not registered yet\n");
> +		return 0;
> +	}
> +
> +	return v4l2_subdev_call(csi2dc->input_sd, video, g_frame_interval,
> +				interval);
> +}
> +
> +static int csi2dc_s_frame_interval(struct v4l2_subdev *csi2dc_sd,
> +				   struct v4l2_subdev_frame_interval *interval)
> +{
> +	struct csi2dc_device *csi2dc = csi2dc_sd_to_csi2dc_device(csi2dc_sd);
> +
> +	if (!csi2dc->completed) {
> +		dev_dbg((csi2dc)->dev, "subdev not registered yet\n");
> +		return 0;
> +	}
> +
> +	return v4l2_subdev_call(csi2dc->input_sd, video, s_frame_interval,
> +				interval);
> +}
> +
> +static int csi2dc_enum_frame_size(struct v4l2_subdev *csi2dc_sd,
> +				  struct v4l2_subdev_pad_config *cfg,
> +				  struct v4l2_subdev_frame_size_enum *fse)
> +{
> +	struct csi2dc_device *csi2dc = csi2dc_sd_to_csi2dc_device(csi2dc_sd);
> +
> +	if (!csi2dc->completed) {
> +		dev_dbg((csi2dc)->dev, "subdev not registered yet\n");
> +		return 0;
> +	}
> +
> +	return v4l2_subdev_call(csi2dc->input_sd, pad, enum_frame_size, cfg,
> +				fse);
> +}
> +
> +static int csi2dc_enum_frame_interval(struct v4l2_subdev *csi2dc_sd,
> +			      struct v4l2_subdev_pad_config *cfg,
> +			      struct v4l2_subdev_frame_interval_enum *fie)
> +{
> +	struct csi2dc_device *csi2dc = csi2dc_sd_to_csi2dc_device(csi2dc_sd);
> +
> +	if (!csi2dc->completed) {
> +		dev_dbg((csi2dc)->dev, "subdev not registered yet\n");
> +		return 0;
> +	}
> +
> +	return v4l2_subdev_call(csi2dc->input_sd, pad, enum_frame_interval, cfg,
> +				fie);
> +}
> +
> +static const struct v4l2_subdev_pad_ops csi2dc_pad_ops = {
> +	.enum_mbus_code = csi2dc_enum_mbus_code,
> +	.set_fmt = csi2dc_set_fmt,
> +	.enum_frame_size = csi2dc_enum_frame_size,
> +	.enum_frame_interval = csi2dc_enum_frame_interval,
> +};
> +
> +static const struct v4l2_subdev_video_ops csi2dc_video_ops = {
> +	.s_stream = csi2dc_s_stream,
> +	.g_frame_interval = csi2dc_g_frame_interval,
> +	.s_frame_interval = csi2dc_s_frame_interval,
> +};
> +
> +static const struct v4l2_subdev_ops csi2dc_subdev_ops = {
> +	.pad = &csi2dc_pad_ops,
> +	.video = &csi2dc_video_ops,
> +};
> +
> +static int csi2dc_get_mbus_config(struct csi2dc_device *csi2dc)
> +{
> +	struct v4l2_mbus_config mbus_config = { 0 };
> +	int ret;
> +
> +	ret = v4l2_subdev_call(csi2dc->input_sd, pad, get_mbus_config,
> +			       csi2dc->remote_pad, &mbus_config);
> +	if (ret == -ENOIOCTLCMD) {
> +		dev_dbg(csi2dc->dev,
> +			"no remote mbus configuration available\n");
> +		goto csi2dc_get_mbus_config_defaults;
> +	}
> +
> +	if (ret) {
> +		dev_err(csi2dc->dev,
> +			"failed to get remote mbus configuration\n");
> +		goto csi2dc_get_mbus_config_defaults;

This should probably be an error reported to the caller. But this
function return value is not checked, so it's probably fine.

> +	}
> +
> +	if (mbus_config.flags & V4L2_MBUS_CSI2_CHANNEL_0)
> +		csi2dc->vc = 0;
> +	else if (mbus_config.flags & V4L2_MBUS_CSI2_CHANNEL_1)
> +		csi2dc->vc = 1;
> +	else if (mbus_config.flags & V4L2_MBUS_CSI2_CHANNEL_2)
> +		csi2dc->vc = 2;
> +	else if (mbus_config.flags & V4L2_MBUS_CSI2_CHANNEL_3)
> +		csi2dc->vc = 3;
> +
> +	dev_dbg(csi2dc->dev, "subdev sending on channel %d\n", csi2dc->vc);
> +
> +	csi2dc->clk_gated = mbus_config.flags &
> +			    V4L2_MBUS_CSI2_NONCONTINUOUS_CLOCK;
> +
> +	dev_dbg(csi2dc->dev, "%s clock\n",
> +		csi2dc->clk_gated ? "gated" : "free running");
> +
> +	return 0;
> +
> +csi2dc_get_mbus_config_defaults:
> +	csi2dc->vc = 0; /* Virtual ID 0 by default */
> +	csi2dc->clk_gated = false; /* Free running clock by default */
> +
> +	return 0;
> +}
> +
> +static int csi2dc_async_bound(struct v4l2_async_notifier *notifier,
> +			      struct v4l2_subdev *subdev,
> +			      struct v4l2_async_subdev *asd)
> +{
> +	struct csi2dc_device *csi2dc = container_of(notifier->v4l2_dev,
> +					struct csi2dc_device, v4l2_dev);
> +	int pad;
> +
> +	csi2dc->input_sd = subdev;
> +
> +	pad = media_entity_get_fwnode_pad(&subdev->entity,
> +					  asd->match.fwnode,
> +					  MEDIA_PAD_FL_SOURCE);
> +	if (pad < 0) {
> +		dev_err(csi2dc->dev, "Failed to find pad for %s\n",
> +			subdev->name);
> +		return pad;
> +	}
> +
> +	csi2dc->remote_pad = pad;
> +
> +	csi2dc_get_mbus_config(csi2dc);

The closer to s_stream you call get_mbus_config, the less the chances
of receiving a stale configuration, if this can happen.

> +
> +	return 0;
> +}
> +
> +static int csi2dc_async_complete(struct v4l2_async_notifier *notifier)
> +{
> +	struct csi2dc_device *csi2dc =
> +		container_of(notifier->v4l2_dev, struct csi2dc_device,
> +			     v4l2_dev);
> +	int ret;
> +
> +	ret = csi2dc_formats_init(csi2dc);
> +	if (ret)
> +		return ret;
> +
> +	ret = v4l2_device_register_subdev_nodes(&csi2dc->v4l2_dev);
> +	if (ret < 0) {
> +		v4l2_err(&csi2dc->v4l2_dev,
> +			 "failed to register subdev nodes\n");
> +		return ret;
> +	}
> +
> +	csi2dc->completed = true;
> +
> +	csi2dc_writel(csi2dc, CSI2DC_GCFG,
> +		      (SAMA7G5_HLC & CSI2DC_GCFG_HLC_MASK) |
> +		      (csi2dc->clk_gated ? 0 : CSI2DC_GCFG_MIPIFRN));
> +
> +	csi2dc_writel(csi2dc, CSI2DC_VPCOL,
> +		      CSI2DC_VPCOL_COL(0xFFF) & CSI2DC_VPCOL_COL_MASK);
> +	csi2dc_writel(csi2dc, CSI2DC_VPROW,
> +		      CSI2DC_VPROW_ROW(0xFFF) & CSI2DC_VPROW_ROW_MASK);
> +
> +	/* once we are completed, we can register ourselves in the pipeline */
> +	schedule_work(&csi2dc->workq);
> +
> +	return ret;
> +}
> +
> +static const struct v4l2_async_notifier_operations csi2dc_async_ops = {
> +	.bound = csi2dc_async_bound,
> +	.complete = csi2dc_async_complete,
> +};
> +
> +static void csi2dc_cleanup_notifier(struct csi2dc_device *csi2dc)
> +{
> +	v4l2_async_notifier_unregister(&csi2dc->notifier);
> +	v4l2_async_notifier_cleanup(&csi2dc->notifier);
> +}
> +
> +static int csi2dc_prepare_notifier(struct csi2dc_device *csi2dc,
> +				   struct device_node *input_parent)
> +{
> +	int ret;
> +
> +	v4l2_async_notifier_init(&csi2dc->notifier);
> +
> +	csi2dc->asd = kzalloc(sizeof(*csi2dc->asd), GFP_KERNEL);
> +	if (!csi2dc->asd)
> +		return -ENOMEM;
> +
> +	csi2dc->asd->match_type = V4L2_ASYNC_MATCH_FWNODE;
> +	csi2dc->asd->match.fwnode = of_fwnode_handle(input_parent);

If you use v4l2_async_notifier_add_fwnode_subdev() the framework does
this for you.

> +
> +	ret = v4l2_async_notifier_add_subdev(&csi2dc->notifier, csi2dc->asd);
> +	if (ret) {
> +		dev_err(csi2dc->dev, "failed to add async notifier.\n");
> +		v4l2_async_notifier_cleanup(&csi2dc->notifier);
> +		goto csi2dc_prepare_notifier_err;
> +	}
> +
> +	csi2dc->notifier.ops = &csi2dc_async_ops;
> +
> +	ret = v4l2_async_notifier_register(&csi2dc->v4l2_dev,
> +					   &csi2dc->notifier);
> +
> +	if (ret) {
> +		dev_err(csi2dc->dev, "fail to register async notifier.\n");

Shouldn't you cleanup the notifier if registration fails ?

> +		goto csi2dc_prepare_notifier_err;
> +	}
> +
> +csi2dc_prepare_notifier_err:
> +	of_node_put(input_parent);
> +
> +	return ret;
> +}
> +
> +static int csi2dc_of_parse(struct csi2dc_device *csi2dc,
> +			   struct device_node *of_node)
> +{
> +	struct device_node *input_node, *sink_node, *input_parent;
> +	struct v4l2_fwnode_endpoint input_endpoint = { 0 },
> +				    sink_endpoint = { 0 };
> +	int ret;
> +
> +	input_node = of_graph_get_next_endpoint(of_node, NULL);
> +
> +	if (!input_node) {
> +		dev_err(csi2dc->dev,
> +			"missing port node at %s, input node is mandatory.\n",

Please use %pOF to print the node name
Also, input_node should be put in the error path

> +			of_node->full_name);
> +		return -EINVAL;
> +	}
> +
> +	ret = v4l2_fwnode_endpoint_parse(of_fwnode_handle(input_node),
> +					 &input_endpoint);

Please set input_endpoint.bus_type if you know what kind of bus you're
dealing with (not having the bindings of the IDI transmitter I'm not
sure. Is this V4L2_MBUS_CSI2_DPHY ?)

> +
> +	if (ret) {
> +		dev_err(csi2dc->dev, "endpoint not defined at %s\n",
> +			of_node->full_name);
> +		return ret;
> +	}
> +
> +	input_parent = of_graph_get_remote_port_parent(input_node);
> +	if (!input_parent) {

Missing of_node_put(input_node)

> +		dev_err(csi2dc->dev,
> +			"could not get input node's parent node.\n");
> +		return -EINVAL;
> +	}
> +
> +	sink_node = of_graph_get_next_endpoint(of_node, input_node);
> +
> +	if (sink_node)
> +		ret = v4l2_fwnode_endpoint_parse(of_fwnode_handle(sink_node),
> +						 &sink_endpoint);

Same, set sink_endpoint.bus_type if you know it's MBUS_PARALLEL

> +
> +	if (!sink_node || ret) {

If parsing fail you don't return an error but continue registering the
notifier and potentially end up registering the async subdev for this
entity even if the endpoint parsing failed.

> +		dev_info(csi2dc->dev,
> +			 "missing sink node at %s, data pipe available only.\n",
> +			 of_node->full_name);
> +	} else {
> +		csi2dc->video_pipe = true;

video_pipe is unused it seems

> +
> +		dev_dbg(csi2dc->dev, "block %s %d.%d->%d.%d video pipeline\n",
> +			of_node->full_name, input_endpoint.base.port,
> +			input_endpoint.base.id,	sink_endpoint.base.port,
> +			sink_endpoint.base.id);
> +	}
> +
> +	of_node_put(sink_node);
> +	of_node_put(input_node);
> +
> +	/* prepare async notifier for subdevice completion */
> +	return csi2dc_prepare_notifier(csi2dc, input_parent);
> +}
> +
> +static void csi2dc_workq_handler(struct work_struct *workq)
> +{
> +	struct csi2dc_device *csi2dc = container_of(workq,
> +					struct csi2dc_device, workq);
> +	int ret;
> +
> +	if (v4l2_async_register_subdev(&csi2dc->csi2dc_sd))
> +		dev_dbg(csi2dc->dev, "failed to register the subdevice\n");

That's peculiar, why do you have to schedule this to a workqueue
instead of doing this in the complete() callback ?

> +
> +	ret = csi2dc_power(csi2dc, true);
> +	if (ret < 0)
> +		v4l2_err(&csi2dc->v4l2_dev, "failed to power on\n");

Should the device be powered on at s_stream time ? Possibly with a
pm_runtime_get_sync() call ? I see you register pm_runtime operations,
but never call get_sync() or _put().

What if CONFIG_PM not selected ? Should this driver select it ? Do you
have use cases where that's not possible ?

> +}
> +
> +static int csi2dc_probe(struct platform_device *pdev)
> +{
> +	struct device *dev = &pdev->dev;
> +	struct csi2dc_device *csi2dc;
> +	struct resource *res = NULL;
> +	int ret = 0;
> +
> +	csi2dc = devm_kzalloc(dev, sizeof(*csi2dc), GFP_KERNEL);
> +	if (!csi2dc)
> +		return -ENOMEM;
> +
> +	csi2dc->dev = dev;
> +
> +	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
> +	if (!res)
> +		return -EINVAL;

devm_ioremap_resource() checks for the validity of 'res' so you can
drop the previous two lines

> +
> +	csi2dc->base = devm_ioremap_resource(dev, res);
> +

Is the empy line intentional, sometimes you have one, sometimes you
don't ?

> +	if (IS_ERR(csi2dc->base)) {
> +		dev_err(dev, "base address not set\n");


> +		return PTR_ERR(csi2dc->base);
> +	}
> +
> +	csi2dc->pclk = devm_clk_get(dev, "pclk");
> +	if (IS_ERR(csi2dc->pclk)) {
> +		ret = PTR_ERR(csi2dc->pclk);
> +		dev_err(dev, "failed to get pclk: %d\n", ret);
> +		return ret;

Just return PTR_ERR instead of assigning to ret

> +	}
> +
> +	ret = clk_prepare_enable(csi2dc->pclk);
> +	if (ret) {
> +		dev_err(dev, "failed to enable pclk: %d\n", ret);
> +		return ret;
> +	}

Has this clock to be enabled here or can it be done in the
pm_runtime callback ?

> +
> +	csi2dc->scck = devm_clk_get(dev, "scck");
> +	if (IS_ERR(csi2dc->scck)) {
> +		ret = PTR_ERR(csi2dc->scck);
> +		dev_err(dev, "failed to get scck: %d\n", ret);
> +		goto csi2dc_clk_fail;
> +	}
> +
> +	ret = v4l2_device_register(dev, &csi2dc->v4l2_dev);
> +	if (ret) {
> +		dev_err(dev, "unable to register v4l2 device.\n");
> +		goto csi2dc_clk_fail;
> +	}
> +
> +	v4l2_subdev_init(&csi2dc->csi2dc_sd, &csi2dc_subdev_ops);
> +
> +	csi2dc->csi2dc_sd.owner = THIS_MODULE;
> +	csi2dc->csi2dc_sd.dev = dev;
> +	snprintf(csi2dc->csi2dc_sd.name, sizeof(csi2dc->csi2dc_sd.name),
> +		 "CSI2DC.0");
> +
> +	csi2dc->csi2dc_sd.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE;
> +	csi2dc->csi2dc_sd.entity.function = MEDIA_ENT_F_VID_IF_BRIDGE;
> +	csi2dc->pads[CSI2DC_PAD_SINK].flags = MEDIA_PAD_FL_SINK;
> +	csi2dc->pads[CSI2DC_PAD_SOURCE].flags = MEDIA_PAD_FL_SOURCE;

Isn't the source pad presence conditional to the presence of
port@1 ?

> +
> +	ret = media_entity_pads_init(&csi2dc->csi2dc_sd.entity, CSI2DC_PADS_NUM,
> +				     csi2dc->pads);
> +	if (ret < 0) {
> +		dev_err(dev, "media entity init failed\n");
> +		goto csi2dc_probe_entity_err;
> +	}
> +
> +	v4l2_set_subdevdata(&csi2dc->csi2dc_sd, pdev);
> +
> +	platform_set_drvdata(pdev, &csi2dc->csi2dc_sd);
> +
> +	INIT_WORK(&csi2dc->workq, csi2dc_workq_handler);
> +
> +	ret = csi2dc_of_parse(csi2dc, dev->of_node);
> +	if (ret)
> +		goto csi2dc_probe_entity_err;
> +
> +	dev_info(dev, "Microchip CSI2DC version %x\n",
> +		 csi2dc_readl(csi2dc, CSI2DC_VERSION));
> +
> +	pm_runtime_set_active(dev);
> +	pm_runtime_enable(dev);
> +	pm_request_idle(dev);
> +
> +	return 0;
> +
> +csi2dc_probe_entity_err:
> +	media_entity_cleanup(&csi2dc->csi2dc_sd.entity);
> +	v4l2_device_unregister(&csi2dc->v4l2_dev);
> +csi2dc_clk_fail:
> +	clk_disable_unprepare(csi2dc->pclk);
> +	return ret;
> +}
> +
> +static int csi2dc_remove(struct platform_device *pdev)
> +{
> +	struct v4l2_subdev *csi2dc_sd = platform_get_drvdata(pdev);
> +	struct csi2dc_device *csi2dc = csi2dc_sd_to_csi2dc_device(csi2dc_sd);
> +
> +	pm_runtime_disable(&pdev->dev);
> +
> +	v4l2_async_unregister_subdev(&csi2dc->csi2dc_sd);
> +	csi2dc_cleanup_notifier(csi2dc);
> +	media_entity_cleanup(&csi2dc->csi2dc_sd.entity);
> +	v4l2_device_unregister(&csi2dc->v4l2_dev);
> +	clk_disable_unprepare(csi2dc->pclk);
> +
> +	return 0;
> +}
> +
> +static int __maybe_unused csi2dc_runtime_suspend(struct device *dev)
> +{
> +	struct csi2dc_device *csi2dc = dev_get_drvdata(dev);
> +
> +	return csi2dc_power(csi2dc, false);
> +}
> +
> +static int __maybe_unused csi2dc_runtime_resume(struct device *dev)
> +{
> +	struct csi2dc_device *csi2dc = dev_get_drvdata(dev);
> +
> +	return csi2dc_power(csi2dc, true);
> +}
> +
> +static const struct dev_pm_ops csi2dc_dev_pm_ops = {
> +	SET_RUNTIME_PM_OPS(csi2dc_runtime_suspend, csi2dc_runtime_resume, NULL)
> +};
> +
> +static const struct of_device_id csi2dc_of_match[] = {
> +	{ .compatible = "microchip,sama7g5-csi2dc" },
> +	{ }
> +};
> +
> +MODULE_DEVICE_TABLE(of, csi2dc_of_match);
> +
> +static struct platform_driver csi2dc_driver = {
> +	.probe	= csi2dc_probe,
> +	.remove	= csi2dc_remove,
> +	.driver	= {
> +		.name		= "microchip-csi2dc",
> +		.pm		= &csi2dc_dev_pm_ops,
> +		.of_match_table = of_match_ptr(csi2dc_of_match),
> +	},
> +};
> +
> +module_platform_driver(csi2dc_driver);
> +
> +MODULE_AUTHOR("Eugen Hristev <eugen.hristev@microchip.com>");
> +MODULE_DESCRIPTION("Microchip CSI2 Demux Controller driver");
> +MODULE_LICENSE("GPL v2");
> +MODULE_SUPPORTED_DEVICE("video");

For my education, what's MODULE_SUPPORTED_DEVICE for ?

Thanks
  j

> --
> 2.25.1
>