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Date:   Thu, 14 Jul 2022 17:56:41 +0200
From:   Jacopo Mondi <jacopo@jmondi.org>
To:     Yassine Oudjana <yassine.oudjana@gmail.com>
Cc:     Mauro Carvalho Chehab <mchehab@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Tianshu Qiu <tian.shu.qiu@intel.com>,
        Bingbu Cao <bingbu.cao@intel.com>,
        Yassine Oudjana <y.oudjana@protonmail.com>,
        linux-media@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2 3/3] media: i2c: ak7375: Add regulator management
Message-ID: <20220714155641.evcukqkdffipfnbk@uno.localdomain>
References: <20220711144039.232196-1-y.oudjana@protonmail.com>
 <20220711144039.232196-4-y.oudjana@protonmail.com>
 <20220711173123.55abjsli3tmqgegj@uno.localdomain>
 <52K0FR.YCGQA83H5U3W@gmail.com>
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Hi Yassine,

On Thu, Jul 14, 2022 at 05:56:29PM +0400, Yassine Oudjana wrote:
>
> On Mon, Jul 11 2022 at 19:31:23 +0200, Jacopo Mondi <jacopo@jmondi.org>
> wrote:
> > Hi Yassine,
> >
> > On Mon, Jul 11, 2022 at 06:40:39PM +0400, Yassine Oudjana wrote:
> > >  From: Yassine Oudjana <y.oudjana@protonmail.com>
> > >
> > >  Make the driver get needed regulators on probe and enable/disable
> > >  them on runtime PM callbacks.
> > >
> > >  Signed-off-by: Yassine Oudjana <y.oudjana@protonmail.com>
> > >  ---
> > >  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));
> >
> > Why are you using %pe here ? Your return value is not a pointer
>
> In order to have it print a symbolic error name instead of a value
> with CONFIG_SYMBOLIC_ERRNAME=y. There is no format code for an
> error integer (or at least I couldn't find one mentioned anywhere
> in the docs), so instead I use %pe then wrap `ret` in ERR_PTR().
>

Ah nice, sorry I didn't realize. I grepped around in drivers/media and
saw it only used with pointer values, but I actually missed two
drivers that wrap ret in ERR_PTR() like you're doing here.

> > (Also, missing \n at the end of the string)
>
> That wasn't intentional. I'll fix it.
>

That's indeed minor.
Let me reply to the other email about delays..


> >
> > From Documentation/core-api/printk-formats.rst:
> > 	%pe	-ENOSPC
> >
> > For printing error pointers (i.e. a pointer for which IS_ERR() is true)
> > as a symbolic error name. Error values for which no symbolic name is
> > known are printed in decimal, while a non-ERR_PTR passed as the
> > argument to %pe gets treated as ordinary %p.
> >
> > >  +		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
> > >
>
>