linux-kernel - Re: [PATCH v2 3/3] media: i2c: ak7375: Add regulator management

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Message-ID: <20220720105842.00006db4@arducam.com>
Date:   Wed, 20 Jul 2022 10:58:42 +0800
From:   Lee Jackson <info@...ucam.com>
To:     jacopo@...ndi.org
Cc:     bingbu.cao@...el.com, devicetree@...r.kernel.org, info@...ucam.com,
        krzysztof.kozlowski+dt@...aro.org, linux-kernel@...r.kernel.org,
        linux-media@...r.kernel.org, mchehab@...nel.org,
        robh+dt@...nel.org, tian.shu.qiu@...el.com,
        y.oudjana@...tonmail.com, yassine.oudjana@...il.com
Subject: Re: [PATCH v2 3/3] media: i2c: ak7375: Add regulator management

Hello All,

This is Lee Jackson from Arducam, please check the reply following.

On Thu, 14 Jul 2022 17:58:31 +0200
Jacopo Mondi <jacopo@...ndi.org> wrote:

> Hello Yassine
> 
> On Thu, Jul 14, 2022 at 06:06:32PM +0400, Yassine Oudjana wrote:
> >
> > On Wed, Jul 13 2022 at 09:39:51 +0200, Jacopo Mondi
> > <jacopo@...ndi.org> wrote:  
> > > Hi Yassine
> > >
> > > On Mon, Jul 11, 2022 at 06:40:39PM +0400, Yassine Oudjana wrote:  
> > > >  From: Yassine Oudjana <y.oudjana@...tonmail.com>
> > > >
> > > >  Make the driver get needed regulators on probe and
> > > > enable/disable them on runtime PM callbacks.
> > > >
> > > >  Signed-off-by: Yassine Oudjana <y.oudjana@...tonmail.com>  
> > >
> > > Have you seen this ?
> > > https://github.com/ArduCAM/IMX519_AK7375/blob/main/AK7375/0002-media-i2c-ak7375-driver-add-optional-regulator-suppo.patch#L172
> > >
> > > It claims
> > > +	* Initialisation delay between VDD low->high and the
> > > moment
> > > +	* when the i2c command is available.
> > > +	* From the datasheet, it should be 10ms + 2ms (max power
> > > +	* up sequence duration)
> > >
> > > 10ms seems like a long time, it would be nice to have the
> > > datasheet to cross-check.  
> >
> > It does seem quite long. I couldn't find a datasheet anywhere
> > so the value I discovered is the best I have. I've added the
> > author of that patch to CC; maybe they have some info to
> > contribute.
> >  
> 
> I have now tested these patches with an Arducam IMX519 camera.
> Using a 3msec delay I get failures in the establishing i2c
> communications (I only tested 2 times though).
> 
> With 10milliseconds (which I concur is a lot) I get stable results.
> Let's see if we can get more info from who has the manual.
> 
> Thanks
>   j
> 

We have the datasheet for the ak7371 and as far as we know they are not
much different, here is the power up sequence for the ak7371:
https://www.arducam.com/wp-content/uploads/2022/07/ak7371-power-sequence.png
(We're not very familiar with working on the linux kernel mailing list
yet, that's one reason we didn't submit ak7375patch, please let me know
if I'm doing something wrong.)

> > >
> > > Thanks
> > >    j
> > >  
> > > >  ---
> > > >  Changes since v1:
> > > >    - Reorganize variable declaration
> > > >    - Change the power-on delay range to 3000-3500 microseconds.
> > > >
> > > >   drivers/media/i2c/ak7375.c | 39
> > > > ++++++++++++++++++++++++++++++++++++++
> > > >   1 file changed, 39 insertions(+)
> > > >
> > > >  diff --git a/drivers/media/i2c/ak7375.c
> > > > b/drivers/media/i2c/ak7375.c index 40b1a4aa846c..c2b2542a0056
> > > > 100644 --- a/drivers/media/i2c/ak7375.c
> > > >  +++ b/drivers/media/i2c/ak7375.c
> > > >  @@ -6,6 +6,7 @@
> > > >   #include <linux/i2c.h>
> > > >   #include <linux/module.h>
> > > >   #include <linux/pm_runtime.h>
> > > >  +#include <linux/regulator/consumer.h>
> > > >   #include <media/v4l2-ctrls.h>
> > > >   #include <media/v4l2-device.h>
> > > >
> > > >  @@ -23,17 +24,32 @@
> > > >    */
> > > >   #define AK7375_CTRL_STEPS	64
> > > >   #define AK7375_CTRL_DELAY_US	1000
> > > >  +/*
> > > >  + * The vcm takes around 3 ms to power on and start taking
> > > >  + * I2C messages. This value was found experimentally due to
> > > >  + * lack of documentation.
> > > >  + */
> > > >  +#define AK7375_POWER_DELAY_US	3000
> > > >
> > > >   #define AK7375_REG_POSITION	0x0
> > > >   #define AK7375_REG_CONT		0x2
> > > >   #define AK7375_MODE_ACTIVE	0x0
> > > >   #define AK7375_MODE_STANDBY	0x40
> > > >
> > > >  +static const char * const ak7375_supply_names[] = {
> > > >  +	"vdd",
> > > >  +	"vio",
> > > >  +};
> > > >  +
> > > >  +#define AK7375_NUM_SUPPLIES ARRAY_SIZE(ak7375_supply_names)
> > > >  +
> > > >   /* ak7375 device structure */
> > > >   struct ak7375_device {
> > > >   	struct v4l2_ctrl_handler ctrls_vcm;
> > > >   	struct v4l2_subdev sd;
> > > >   	struct v4l2_ctrl *focus;
> > > >  +	struct regulator_bulk_data
> > > > supplies[AK7375_NUM_SUPPLIES]; +
> > > >   	/* active or standby mode */
> > > >   	bool active;
> > > >   };
> > > >  @@ -133,12 +149,24 @@ static int ak7375_probe(struct i2c_client
> > > > *client)
> > > >   {
> > > >   	struct ak7375_device *ak7375_dev;
> > > >   	int ret;
> > > >  +	int i;
> > > >
> > > >   	ak7375_dev = devm_kzalloc(&client->dev,
> > > > sizeof(*ak7375_dev), GFP_KERNEL);
> > > >   	if (!ak7375_dev)
> > > >   		return -ENOMEM;
> > > >
> > > >  +	for (i = 0; i < AK7375_NUM_SUPPLIES; i++)
> > > >  +		ak7375_dev->supplies[i].supply =
> > > > ak7375_supply_names[i]; +
> > > >  +	ret = devm_regulator_bulk_get(&client->dev,
> > > > AK7375_NUM_SUPPLIES,
> > > >  +				      ak7375_dev->supplies);
> > > >  +	if (ret) {
> > > >  +		dev_err(&client->dev, "Failed to get
> > > > regulators: %pe",
> > > >  +			ERR_PTR(ret));
> > > >  +		return ret;
> > > >  +	}
> > > >  +
> > > >   	v4l2_i2c_subdev_init(&ak7375_dev->sd, client,
> > > > &ak7375_ops); ak7375_dev->sd.flags |=
> > > > V4L2_SUBDEV_FL_HAS_DEVNODE; ak7375_dev->sd.internal_ops =
> > > > &ak7375_int_ops; @@ -210,6 +238,10 @@ static int __maybe_unused
> > > > ak7375_vcm_suspend(struct device *dev)
> > > >   	if (ret)
> > > >   		dev_err(dev, "%s I2C failure: %d\n",
> > > > __func__, ret);
> > > >
> > > >  +	ret = regulator_bulk_disable(AK7375_NUM_SUPPLIES,
> > > > ak7375_dev->supplies);
> > > >  +	if (ret)
> > > >  +		return ret;
> > > >  +
> > > >   	ak7375_dev->active = false;
> > > >
> > > >   	return 0;
> > > >  @@ -230,6 +262,13 @@ static int __maybe_unused
> > > > ak7375_vcm_resume(struct device *dev)
> > > >   	if (ak7375_dev->active)
> > > >   		return 0;
> > > >
> > > >  +	ret = regulator_bulk_enable(AK7375_NUM_SUPPLIES,
> > > > ak7375_dev->supplies);
> > > >  +	if (ret)
> > > >  +		return ret;
> > > >  +
> > > >  +	/* Wait for vcm to become ready */
> > > >  +	usleep_range(AK7375_POWER_DELAY_US,
> > > > AK7375_POWER_DELAY_US + 500); +
> > > >   	ret = ak7375_i2c_write(ak7375_dev, AK7375_REG_CONT,
> > > >   		AK7375_MODE_ACTIVE, 1);
> > > >   	if (ret) {
> > > >  --
> > > >  2.37.0
> > > >  
> >
> >