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Reply-To: kieran.bingham+renesas@ideasonboard.com
Subject: Re: [PATCH v9 2/4] media: i2c: Add MAX9286 driver
To:     Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc:     linux-renesas-soc@vger.kernel.org, linux-media@vger.kernel.org,
        devicetree@vger.kernel.org, linux-kernel@vger.kernel.org,
        Mauro Carvalho Chehab <mchehab@kernel.org>,
        Kieran Bingham <kieran.bingham@ideasonboard.com>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Jacopo Mondi <jacopo@jmondi.org>,
        =?UTF-8?Q?Niklas_S=c3=b6derlund?= <niklas.soderlund@ragnatech.se>,
        sakari.ailus@iki.fi, Hans Verkuil <hverkuil@xs4all.nl>,
        Hyun Kwon <hyunk@xilinx.com>, Rob Herring <robh+dt@kernel.org>,
        Jacopo Mondi <jacopo+renesas@jmondi.org>,
        Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>,
        =?UTF-8?Q?Niklas_S=c3=b6derlund?= 
        <niklas.soderlund+renesas@ragnatech.se>
References: <20200512155105.1068064-1-kieran.bingham+renesas@ideasonboard.com>
 <20200512155105.1068064-3-kieran.bingham+renesas@ideasonboard.com>
 <20200512181706.GA21014@Mani-XPS-13-9360>
 <11aca587-9438-4fba-081c-b82631e96989@ideasonboard.com>
 <20200514101356.GF2877@Mani-XPS-13-9360>
From:   Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
Organization: Ideas on Board
Message-ID: <f46ed5fc-4eb0-8841-25b8-ef6c45e7ac87@ideasonboard.com>
Date:   Thu, 14 May 2020 12:47:35 +0100
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On 14/05/2020 11:13, Manivannan Sadhasivam wrote:
> Hi Kieran,
> 
> On Thu, May 14, 2020 at 11:02:53AM +0100, Kieran Bingham wrote:
>> Hi Mani,
>>
>> On 12/05/2020 19:17, Manivannan Sadhasivam wrote:
>>> On Tue, May 12, 2020 at 04:51:03PM +0100, Kieran Bingham wrote:
>>>> The MAX9286 is a 4-channel GMSL deserializer with coax or STP input and
>>>> CSI-2 output. The device supports multicamera streaming applications,
>>>> and features the ability to synchronise the attached cameras.
>>>>
>>>> CSI-2 output can be configured with 1 to 4 lanes, and a control channel
>>>> is supported over I2C, which implements an I2C mux to facilitate
>>>> communications with connected cameras across the reverse control
>>>> channel.
>>>>
>>>> Signed-off-by: Jacopo Mondi <jacopo+renesas@jmondi.org>
>>>> Signed-off-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
>>>> Signed-off-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
>>>> Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
>>>>
>>>> --
>>>> v2:
>>>>  - Fix MAINTAINERS entry
>>>>
>>>> This posting is released with the following modifications to work
>>>> without Sakari's VC developments:
>>>>  - max9286_g_mbus_config() re-instated
>>>>  - max9286_get_frame_desc() is not bus/csi aware
>>>>  - max9286_{get,set}_routing() removed
>>>>
>>>> v3:
>>>>  - Initialise notifier with v4l2_async_notifier_init
>>>>  - Update for new mbus csi2 format V4L2_MBUS_CSI2_DPHY
>>>>
>>>> v4: - Re-introduce required code to function with the VC series.
>>>>
>>>>  - Implement max9286_get_routing, max9286_set_routing
>>>>  - Remove max9286_g_mbus_config
>>>>
>>>> v5: (internal release)
>>>>  - Fix printk formatting for hex value
>>>>  - max9286->sd.flags |= V4L2_SUBDEV_FL_HAS_DEVNODE (add |)
>>>>  - MEDIA_ENT_F_PROC_VIDEO_PIXEL_FORMATTER -> MEDIA_ENT_F_VID_IF_BRIDGE
>>>>  - Remove 'device is bound' workaround
>>>>
>>>> v6:
>>>>  - v4l2_subdev_krouting instead of v4l2_subdev_routing separated
>>>>    to allow integration without the VC/V4L2-Mux series.
>>>>  - convert sd_to_max9286 to inline function
>>>>  - rename max9286_device to max9286_priv
>>>>  - Cleanup the v4l2_async_notifier
>>>>  - Extend MODULE_AUTHOR
>>>>  - Replace of_graph_get_endpoint_by_regs with fwnode_graph_get_endpoint_by_id
>>>>  - Pass default bus type when parsing fwnode endpoint (Manivannan Sadhasivam)
>>>>  - Use new YAML file reference in MAINTAINERS
>>>>  - Parse new i2c-mux node in max9286_get_i2c_by_id
>>>>    (This could/should be refactored to parse these separately first)
>>>>  - Spelling and calculation fixes in the FSYNC_LOCKED check comments
>>>>  - Identify each enabled i2c-mux channel in a single pass
>>>>  - max9286: Improve mux-state readbility [v2]
>>>>  - Fix frame sync lock durations
>>>>  - Add comment to describe /why/ we must open the mux in s_stream
>>>>  - use -EXDEV as return code for failed link synchronisation.
>>>>  - Fix reference counting of the dt nodeS
>>>>  - Convert to probe_new for I2C
>>>>  - Remove redundant max9286_i2c_mux_state
>>>>  - Provide optional enable-gpio (max9286-pwdn)
>>>>
>>>> v7:
>>>>  [Kieran]
>>>>  - Ensure powerdown lines are optional
>>>>  - Add a 4ms power-up delay
>>>>  - Add max9286_check_config_link() to core
>>>>  - Add GPIO chip controller for GPIO0OUT and GPIO1OUT
>>>>  - Fix GPIO registration
>>>>  - max9286: Split out async registration
>>>>    (fixes regulator -EPROBE_DEFERs failures)
>>>>  - Collect all V4L2 registrations
>>>>  - balance v4l2_async refcnting
>>>>  - Rename max9286_v4l2_async_ => max9286_v4l2_notifier_
>>>>
>>>>  [Jacopo]
>>>>  - Remove redundanct MAXIM_I2C_SPEED macros
>>>>  - Move notifiers operations
>>>>  - Add delay after reverse channel reconfiguration
>>>>  - Move link setup to completion
>>>>  - Fix up max9286_check_config_link() implementation
>>>>  - Remove redundant dual configuration of reverse channel
>>>>
>>>> v8:
>>>>
>>>> [Kieran]
>>>>  - Update the bound_sources mask on unbind
>>>>  - Convert probe kzalloc usage to devm_ variant
>>>>  - Fix up cleanup path from GPIO PowerDown registration
>>>>  - cleanup GPIO device registration fail path
>>>>  - Convert to use devm_regulator_get()
>>>>  - Fit max9286_parse_dt print on one line
>>>>  - Move multi-device workarounds out of upstream driver
>>>>  - Remove I2C mod-table
>>>>  - Lock format changes
>>>>  - Describe pad index usage
>>>>  - Remove poc_enabled workaround
>>>>  - Rename the max9286_gpio to be more explicit on it's actions.
>>>>  - Move max9286_init_format call
>>>>  - Rework probe sequence and simplify error paths.
>>>>  - Simplify i2c comments
>>>>  - Implement Pixelrate control
>>>>  - Disable overlap window
>>>>
>>>> [Jacopo]
>>>>  - Adapt Kconfig to latest upstream changes
>>>>  - Put of node on error
>>>>  - Calculate pixel rate
>>>>  - Simplify overlap window disablement
>>>>
>>>> v9:
>>>>
>>>> [Kieran]
>>>>  - Kconfig: Depend on OF
>>>>  - Re-sort addition to Makefile
>>>> ---
>>>>  MAINTAINERS                 |   10 +
>>>>  drivers/media/i2c/Kconfig   |   13 +
>>>>  drivers/media/i2c/Makefile  |    1 +
>>>>  drivers/media/i2c/max9286.c | 1332 +++++++++++++++++++++++++++++++++++
>>>>  4 files changed, 1356 insertions(+)
>>>>  create mode 100644 drivers/media/i2c/max9286.c
>>>>
>>>> diff --git a/MAINTAINERS b/MAINTAINERS
>>>> index a7bb6e22d5da..99e3bf7760fd 100644
>>>> --- a/MAINTAINERS
>>>> +++ b/MAINTAINERS
>>>> @@ -10274,6 +10274,16 @@ F:	Documentation/hwmon/max6697.rst
>>>>  F:	drivers/hwmon/max6697.c
>>>>  F:	include/linux/platform_data/max6697.h
>>>>  
>>>> +MAX9286 QUAD GMSL DESERIALIZER DRIVER
>>>> +M:	Jacopo Mondi <jacopo+renesas@jmondi.org>
>>>> +M:	Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
>>>> +M:	Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
>>>> +M:	Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
>>>> +L:	linux-media@vger.kernel.org
>>>> +S:	Maintained
>>>> +F:	Documentation/devicetree/bindings/media/i2c/maxim,max9286.yaml
>>>> +F:	drivers/media/i2c/max9286.c
>>>> +
>>>>  MAX9860 MONO AUDIO VOICE CODEC DRIVER
>>>>  M:	Peter Rosin <peda@axentia.se>
>>>>  L:	alsa-devel@alsa-project.org (moderated for non-subscribers)
>>>> diff --git a/drivers/media/i2c/Kconfig b/drivers/media/i2c/Kconfig
>>>> index 3abc80373ec0..2e390f41f6da 100644
>>>> --- a/drivers/media/i2c/Kconfig
>>>> +++ b/drivers/media/i2c/Kconfig
>>>> @@ -464,6 +464,19 @@ config VIDEO_VPX3220
>>>>  	  To compile this driver as a module, choose M here: the
>>>>  	  module will be called vpx3220.
>>>>  
>>>> +config VIDEO_MAX9286
>>>> +	tristate "Maxim MAX9286 GMSL deserializer support"
>>>> +	depends on I2C && I2C_MUX
>>>> +	depends on OF
>>>> +	select V4L2_FWNODE
>>>> +	select VIDEO_V4L2_SUBDEV_API
>>>> +	select MEDIA_CONTROLLER
>>>> +	help
>>>> +	  This driver supports the Maxim MAX9286 GMSL deserializer.
>>>> +
>>>> +	  To compile this driver as a module, choose M here: the
>>>> +	  module will be called max9286.
>>>> +
>>>>  comment "Video and audio decoders"
>>>>  
>>>>  config VIDEO_SAA717X
>>>> diff --git a/drivers/media/i2c/Makefile b/drivers/media/i2c/Makefile
>>>> index 77bf7d0b691f..f0b001ee4b05 100644
>>>> --- a/drivers/media/i2c/Makefile
>>>> +++ b/drivers/media/i2c/Makefile
>>>> @@ -117,6 +117,7 @@ obj-$(CONFIG_VIDEO_IMX274)	+= imx274.o
>>>>  obj-$(CONFIG_VIDEO_IMX290)	+= imx290.o
>>>>  obj-$(CONFIG_VIDEO_IMX319)	+= imx319.o
>>>>  obj-$(CONFIG_VIDEO_IMX355)	+= imx355.o
>>>> +obj-$(CONFIG_VIDEO_MAX9286)	+= max9286.o
>>>>  obj-$(CONFIG_VIDEO_ST_MIPID02) += st-mipid02.o
>>>>  
>>>>  obj-$(CONFIG_SDR_MAX2175) += max2175.o
>>>> diff --git a/drivers/media/i2c/max9286.c b/drivers/media/i2c/max9286.c
>>>> new file mode 100644
>>>> index 000000000000..481d65f2b51d
>>>> --- /dev/null
>>>> +++ b/drivers/media/i2c/max9286.c
>>>> @@ -0,0 +1,1332 @@
>>>> +// SPDX-License-Identifier: GPL-2.0+
>>>> +/*
>>>> + * Maxim MAX9286 GMSL Deserializer Driver
>>>> + *
>>>> + * Copyright (C) 2017-2019 Jacopo Mondi
>>>> + * Copyright (C) 2017-2019 Kieran Bingham
>>>> + * Copyright (C) 2017-2019 Laurent Pinchart
>>>> + * Copyright (C) 2017-2019 Niklas Söderlund
>>>> + * Copyright (C) 2016 Renesas Electronics Corporation
>>>> + * Copyright (C) 2015 Cogent Embedded, Inc.
>>>> + */
>>>> +
>>>> +#include <linux/delay.h>
>>>> +#include <linux/device.h>
>>>> +#include <linux/fwnode.h>
>>>> +#include <linux/gpio/consumer.h>
>>>> +#include <linux/gpio/driver.h>
>>>> +#include <linux/i2c.h>
>>>> +#include <linux/i2c-mux.h>
>>>> +#include <linux/module.h>
>>>> +#include <linux/mutex.h>
>>>> +#include <linux/of_graph.h>
>>>> +#include <linux/regulator/consumer.h>
>>>> +#include <linux/slab.h>
>>>> +
>>>> +#include <media/v4l2-async.h>
>>>> +#include <media/v4l2-ctrls.h>
>>>> +#include <media/v4l2-device.h>
>>>> +#include <media/v4l2-fwnode.h>
>>>> +#include <media/v4l2-subdev.h>
>>>> +
>>>> +/* Register 0x00 */
>>>> +#define MAX9286_MSTLINKSEL_AUTO		(7 << 5)
>>>> +#define MAX9286_MSTLINKSEL(n)		((n) << 5)
>>>> +#define MAX9286_EN_VS_GEN		BIT(4)
>>>> +#define MAX9286_LINKEN(n)		(1 << (n))
>>>> +/* Register 0x01 */
>>>> +#define MAX9286_FSYNCMODE_ECU		(3 << 6)
>>>> +#define MAX9286_FSYNCMODE_EXT		(2 << 6)
>>>> +#define MAX9286_FSYNCMODE_INT_OUT	(1 << 6)
>>>> +#define MAX9286_FSYNCMODE_INT_HIZ	(0 << 6)
>>>> +#define MAX9286_GPIEN			BIT(5)
>>>> +#define MAX9286_ENLMO_RSTFSYNC		BIT(2)
>>>> +#define MAX9286_FSYNCMETH_AUTO		(2 << 0)
>>>> +#define MAX9286_FSYNCMETH_SEMI_AUTO	(1 << 0)
>>>> +#define MAX9286_FSYNCMETH_MANUAL	(0 << 0)
>>>> +#define MAX9286_REG_FSYNC_PERIOD_L	0x06
>>>> +#define MAX9286_REG_FSYNC_PERIOD_M	0x07
>>>> +#define MAX9286_REG_FSYNC_PERIOD_H	0x08
>>>> +/* Register 0x0a */
>>>> +#define MAX9286_FWDCCEN(n)		(1 << ((n) + 4))
>>>> +#define MAX9286_REVCCEN(n)		(1 << (n))
>>>> +/* Register 0x0c */
>>>> +#define MAX9286_HVEN			BIT(7)
>>>> +#define MAX9286_EDC_6BIT_HAMMING	(2 << 5)
>>>> +#define MAX9286_EDC_6BIT_CRC		(1 << 5)
>>>> +#define MAX9286_EDC_1BIT_PARITY		(0 << 5)
>>>> +#define MAX9286_DESEL			BIT(4)
>>>> +#define MAX9286_INVVS			BIT(3)
>>>> +#define MAX9286_INVHS			BIT(2)
>>>> +#define MAX9286_HVSRC_D0		(2 << 0)
>>>> +#define MAX9286_HVSRC_D14		(1 << 0)
>>>> +#define MAX9286_HVSRC_D18		(0 << 0)
>>>> +/* Register 0x0f */
>>>> +#define MAX9286_0X0F_RESERVED		BIT(3)
>>>> +/* Register 0x12 */
>>>> +#define MAX9286_CSILANECNT(n)		(((n) - 1) << 6)
>>>> +#define MAX9286_CSIDBL			BIT(5)
>>>> +#define MAX9286_DBL			BIT(4)
>>>> +#define MAX9286_DATATYPE_USER_8BIT	(11 << 0)
>>>> +#define MAX9286_DATATYPE_USER_YUV_12BIT	(10 << 0)
>>>> +#define MAX9286_DATATYPE_USER_24BIT	(9 << 0)
>>>> +#define MAX9286_DATATYPE_RAW14		(8 << 0)
>>>> +#define MAX9286_DATATYPE_RAW11		(7 << 0)
>>>> +#define MAX9286_DATATYPE_RAW10		(6 << 0)
>>>> +#define MAX9286_DATATYPE_RAW8		(5 << 0)
>>>> +#define MAX9286_DATATYPE_YUV422_10BIT	(4 << 0)
>>>> +#define MAX9286_DATATYPE_YUV422_8BIT	(3 << 0)
>>>> +#define MAX9286_DATATYPE_RGB555		(2 << 0)
>>>> +#define MAX9286_DATATYPE_RGB565		(1 << 0)
>>>> +#define MAX9286_DATATYPE_RGB888		(0 << 0)
>>>> +/* Register 0x15 */
>>>> +#define MAX9286_VC(n)			((n) << 5)
>>>> +#define MAX9286_VCTYPE			BIT(4)
>>>> +#define MAX9286_CSIOUTEN		BIT(3)
>>>> +#define MAX9286_0X15_RESV		(3 << 0)
>>>> +/* Register 0x1b */
>>>> +#define MAX9286_SWITCHIN(n)		(1 << ((n) + 4))
>>>> +#define MAX9286_ENEQ(n)			(1 << (n))
>>>> +/* Register 0x27 */
>>>> +#define MAX9286_LOCKED			BIT(7)
>>>> +/* Register 0x31 */
>>>> +#define MAX9286_FSYNC_LOCKED		BIT(6)
>>>> +/* Register 0x34 */
>>>> +#define MAX9286_I2CLOCACK		BIT(7)
>>>> +#define MAX9286_I2CSLVSH_1046NS_469NS	(3 << 5)
>>>> +#define MAX9286_I2CSLVSH_938NS_352NS	(2 << 5)
>>>> +#define MAX9286_I2CSLVSH_469NS_234NS	(1 << 5)
>>>> +#define MAX9286_I2CSLVSH_352NS_117NS	(0 << 5)
>>>> +#define MAX9286_I2CMSTBT_837KBPS	(7 << 2)
>>>> +#define MAX9286_I2CMSTBT_533KBPS	(6 << 2)
>>>> +#define MAX9286_I2CMSTBT_339KBPS	(5 << 2)
>>>> +#define MAX9286_I2CMSTBT_173KBPS	(4 << 2)
>>>> +#define MAX9286_I2CMSTBT_105KBPS	(3 << 2)
>>>> +#define MAX9286_I2CMSTBT_84KBPS		(2 << 2)
>>>> +#define MAX9286_I2CMSTBT_28KBPS		(1 << 2)
>>>> +#define MAX9286_I2CMSTBT_8KBPS		(0 << 2)
>>>> +#define MAX9286_I2CSLVTO_NONE		(3 << 0)
>>>> +#define MAX9286_I2CSLVTO_1024US		(2 << 0)
>>>> +#define MAX9286_I2CSLVTO_256US		(1 << 0)
>>>> +#define MAX9286_I2CSLVTO_64US		(0 << 0)
>>>> +/* Register 0x3b */
>>>> +#define MAX9286_REV_TRF(n)		((n) << 4)
>>>> +#define MAX9286_REV_AMP(n)		((((n) - 30) / 10) << 1) /* in mV */
>>>> +#define MAX9286_REV_AMP_X		BIT(0)
>>>> +/* Register 0x3f */
>>>> +#define MAX9286_EN_REV_CFG		BIT(6)
>>>> +#define MAX9286_REV_FLEN(n)		((n) - 20)
>>>> +/* Register 0x49 */
>>>> +#define MAX9286_VIDEO_DETECT_MASK	0x0f
>>>> +/* Register 0x69 */
>>>> +#define MAX9286_LFLTBMONMASKED		BIT(7)
>>>> +#define MAX9286_LOCKMONMASKED		BIT(6)
>>>> +#define MAX9286_AUTOCOMBACKEN		BIT(5)
>>>> +#define MAX9286_AUTOMASKEN		BIT(4)
>>>> +#define MAX9286_MASKLINK(n)		((n) << 0)
>>>> +
>>>> +/*
>>>> + * The sink and source pads are created to match the OF graph port numbers so
>>>> + * that their indexes can be used interchangeably.
>>>> + */
>>>> +#define MAX9286_NUM_GMSL		4
>>>> +#define MAX9286_N_SINKS			4
>>>> +#define MAX9286_N_PADS			5
>>>> +#define MAX9286_SRC_PAD			4
>>>> +
>>>> +struct max9286_source {
>>>> +	struct v4l2_async_subdev asd;
>>>> +	struct v4l2_subdev *sd;
>>>> +	struct fwnode_handle *fwnode;
>>>> +};
>>>> +
>>>> +#define asd_to_max9286_source(_asd) \
>>>> +	container_of(_asd, struct max9286_source, asd)
>>>> +
>>>> +struct max9286_priv {
>>>> +	struct i2c_client *client;
>>>> +	struct gpio_desc *gpiod_pwdn;
>>>> +	struct v4l2_subdev sd;
>>>> +	struct media_pad pads[MAX9286_N_PADS];
>>>> +	struct regulator *regulator;
>>>> +
>>>> +	struct gpio_chip gpio;
>>>> +	u8 gpio_state;
>>>> +
>>>> +	struct i2c_mux_core *mux;
>>>> +	unsigned int mux_channel;
>>>> +	bool mux_open;
>>>> +
>>>> +	struct v4l2_ctrl_handler ctrls;
>>>> +	struct v4l2_ctrl *pixelrate;
>>>> +
>>>> +	struct v4l2_mbus_framefmt fmt[MAX9286_N_SINKS];
>>>> +
>>>> +	/* Protects controls and fmt structures */
>>>> +	struct mutex mutex;
>>>> +
>>>> +	unsigned int nsources;
>>>> +	unsigned int source_mask;
>>>> +	unsigned int route_mask;
>>>> +	unsigned int bound_sources;
>>>> +	unsigned int csi2_data_lanes;
>>>> +	struct max9286_source sources[MAX9286_NUM_GMSL];
>>>> +	struct v4l2_async_notifier notifier;
>>>> +};
>>>> +
>>>
>>> [...]
>>>
>>>> +static int max9286_register_gpio(struct max9286_priv *priv)
>>>> +{
>>>> +	struct device *dev = &priv->client->dev;
>>>> +	struct gpio_chip *gpio = &priv->gpio;
>>>> +	int ret;
>>>> +
>>>> +	static const char * const names[] = {
>>>> +		"GPIO0OUT",
>>>> +		"GPIO1OUT",
>>>> +	};
>>>> +
>>>> +	/* Configure the GPIO */
>>>> +	gpio->label = dev_name(dev);
>>>
>>> So if you have more than one MAX9286 in a system, all gpiochips will appear
>>> with the same name. I'd recommend to append the index to distinguish properly.
>>
>> Ah yes, that's a good point, and I think I've even seen that.
>>
>> I'll fix it now.
>>
>>>
>>>> +	gpio->parent = dev;
>>>> +	gpio->owner = THIS_MODULE;
>>>> +	gpio->of_node = dev->of_node;
>>>> +	gpio->ngpio = 2;
>>>> +	gpio->base = -1;
>>>> +	gpio->set = max9286_gpio_set;
>>>> +	gpio->get = max9286_gpio_get;
>>>> +	gpio->can_sleep = true;
>>>> +	gpio->names = names;
>>>> +
>>>> +	/* GPIO values default to high */
>>>> +	priv->gpio_state = BIT(0) | BIT(1);
>>>> +
>>>> +	ret = devm_gpiochip_add_data(dev, gpio, priv);
>>>> +	if (ret)
>>>> +		dev_err(dev, "Unable to create gpio_chip\n");
>>>> +
>>>> +	return ret;
>>>> +}
>>>> +
>>>
>>> [...]
>>>
>>>> +static int max9286_parse_dt(struct max9286_priv *priv)
>>>> +{
>>>> +	struct device *dev = &priv->client->dev;
>>>> +	struct device_node *i2c_mux;
>>>> +	struct device_node *node = NULL;
>>>> +	unsigned int i2c_mux_mask = 0;
>>>> +
>>>> +	of_node_get(dev->of_node);
>>>
>>> Why this is needed?
>>
>> Hrm .. I recall adding it to solve dt reference balancing.
>>
>> I wish I'd added a comment at the time ... as I can't recall the details
>> now.
>>
> 
> I understand that it is for the refcount balancing but I certainly don't see
> a need for it.

I'll go through and try to validate this again now.

>  
>>>> +	i2c_mux = of_find_node_by_name(dev->of_node, "i2c-mux");
>>>> +	if (!i2c_mux) {
>>>> +		dev_err(dev, "Failed to find i2c-mux node\n");
>>>> +		of_node_put(dev->of_node);
>>>> +		return -EINVAL;
>>>> +	}
>>>> +
> [...]
>>>
>>> [...]
>>>
>>>> +static int max9286_remove(struct i2c_client *client)
>>>> +{
>>>> +	struct max9286_priv *priv = i2c_get_clientdata(client);
>>>> +
>>>> +	i2c_mux_del_adapters(priv->mux);
>>>> +
>>>> +	max9286_v4l2_unregister(priv);
>>>> +
>>>> +	regulator_disable(priv->regulator);
>>>> +
>>>> +	gpiod_set_value_cansleep(priv->gpiod_pwdn, 0);
>>>
>>> Usual power down sequence is to pull the power down gpio low and then turn off
>>> the regulators. This helps in clearing up the internal state machine properly.
>>
>> Do you mean usual, among drivers using regulators? or usual for the max9286?
>>
> 
> Usual for devices exposing shutdown gpios and powered by an external regulator.
> 
>> I have a platform which controls the regulators for the cameras
>> (priv->regulator) through one of the GPIOs provided by the MAX9286.
>>
>> If we powerdown the max9286 first, then we will not be able to change
>> the GPIO value on the gpio controlled regulator.
>>
> 
> Hmm, I didn't think of this usecase. Let's keep it as it is.

Aha indeed it's not clear (especially as the variable is just
'regulator'). The regulator being controlled here does not power the
max9286, but the cameras attached to the max9286 which can be powered up
/ down separately to the max9286.

--
Kieran

> 
> Thanks,
> Mani
> 
>> (Currently it doesn't expose as a gpio regulator, but just a gpio-hog -
>> but thats a different matter)
>>
>> --
>> Kieran
>>
>>
>>>
>>> Thanks,
>>> Mani
>>>
>>>> +
>>>> +	max9286_cleanup_dt(priv);
>>>> +
>>>> +	return 0;
>>>> +}
>>>> +
>>>> +static const struct of_device_id max9286_dt_ids[] = {
>>>> +	{ .compatible = "maxim,max9286" },
>>>> +	{},
>>>> +};
>>>> +MODULE_DEVICE_TABLE(of, max9286_dt_ids);
>>>> +
>>>> +static struct i2c_driver max9286_i2c_driver = {
>>>> +	.driver	= {
>>>> +		.name		= "max9286",
>>>> +		.of_match_table	= of_match_ptr(max9286_dt_ids),
>>>> +	},
>>>> +	.probe_new	= max9286_probe,
>>>> +	.remove		= max9286_remove,
>>>> +};
>>>> +
>>>> +module_i2c_driver(max9286_i2c_driver);
>>>> +
>>>> +MODULE_DESCRIPTION("Maxim MAX9286 GMSL Deserializer Driver");
>>>> +MODULE_AUTHOR("Jacopo Mondi, Kieran Bingham, Laurent Pinchart, Niklas Söderlund, Vladimir Barinov");
>>>> +MODULE_LICENSE("GPL");
>>>> -- 
>>>> 2.25.1
>>>>
>>