linux-kernel - Re: [PATCH v4 2/2] media: i2c: Add GC08A3 image sensor driver

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Message-ID: <115698c0c549e747026cc8841a3bd571533f8e6f.camel@mediatek.com>
Date: Tue, 20 Feb 2024 05:45:54 +0000
From: Zhi Mao (毛智) <zhi.mao@...iatek.com>
To: "laurent.pinchart@...asonboard.com" <laurent.pinchart@...asonboard.com>
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Subject: Re: [PATCH v4 2/2] media: i2c: Add GC08A3 image sensor driver

Hi Laurent,

Thanks for you reply.
I'd like to ask for advice about how to contrl "reset-pin", please
check the below comments.

On Tue, 2024-02-20 at 05:01 +0200, Laurent Pinchart wrote:
>  	 
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
>  Hi Zhi,
> 
> On Tue, Feb 20, 2024 at 02:12:26AM +0000, Zhi Mao (毛智) wrote:
> > On Tue, 2024-02-06 at 20:45 +0200, Laurent Pinchart wrote:
> > > On Sun, Feb 04, 2024 at 02:15:38PM +0800, Zhi Mao wrote:
> > > > Add a V4L2 sub-device driver for Galaxycore GC08A3 image
> sensor.
> > > >
> > > > Signed-off-by: Zhi Mao <zhi.mao@...iatek.com>
> > > > ---
> > > >  drivers/media/i2c/Kconfig  |   10 +
> > > >  drivers/media/i2c/Makefile |    1 +
> > > >  drivers/media/i2c/gc08a3.c | 1448
> ++++++++++++++++++++++++++++++++++++
> > > >  3 files changed, 1459 insertions(+)
> > > >  create mode 100644 drivers/media/i2c/gc08a3.c
> 
> [snip]
> 
> > > > diff --git a/drivers/media/i2c/gc08a3.c
> b/drivers/media/i2c/gc08a3.c
> > > > new file mode 100644
> > > > index 000000000000..3fc7fffb815c
> > > > --- /dev/null
> > > > +++ b/drivers/media/i2c/gc08a3.c
> > > > @@ -0,0 +1,1448 @@
> 
> [snip]
> 
> > > > +static int gc08a3_power_on(struct device *dev)
> > > > +{
> > > > +struct i2c_client *client = to_i2c_client(dev);
> > > > +struct v4l2_subdev *sd = i2c_get_clientdata(client);
> > > > +struct gc08a3 *gc08a3 = to_gc08a3(sd);
> > > > +int ret;
> > > > +
> > > > +ret = regulator_bulk_enable(ARRAY_SIZE(gc08a3_supply_name),
> > > > +    gc08a3->supplies);
> > > > +if (ret < 0) {
> > > > +dev_err(gc08a3->dev, "failed to enable regulators: %d\n",
> ret);
> > > > +return ret;
> > > > +}
> > > > +
> > > > +ret = clk_prepare_enable(gc08a3->xclk);
> > > > +if (ret < 0) {
> > > > +regulator_bulk_disable(ARRAY_SIZE(gc08a3_supply_name),
> > > > +       gc08a3->supplies);
> > > > +dev_err(gc08a3->dev, "clk prepare enable failed\n");
> > > > +return ret;
> > > > +}
> > > > +
> > > > +usleep_range(GC08A3_MIN_SLEEP_US, GC08A3_MAX_SLEEP_US);
> > > > +
> > > > +gpiod_set_value_cansleep(gc08a3->reset_gpio, 1);
> > >
> > > Are you asserting reset when powering on ? That sounds wrong, you
> should
> > > de-assert reset here (and acquire the reset gpio in probe() with
> > > GPIOD_OUT_HIGH). Drivers should use logical levels for GPIOs,
> setting a
> > > GPIO named "reset" to 1 should assert the reset signal, even if
> the
> > > physical signal is active low. You may have the wrong polarity in
> the
> > > device tree.
> >
> > According to the sensor power sequence sepc, "reset" pin should be
> pull
> > from low to high after "dovdd/dvdd/avdd" power on, so I follow this
> > power sequece to pull "reset" pin high in software flow.
> 
> From a hardware point of view that's right, but the Linux kernel
> handles
> logical level of GPIOs. If a GPIO is named "reset", it is expected
> that
> calling
> 
> gpiod_set_value_cansleep(gc08a3->reset_gpio, 1);
> 
> will "assert" the reset signal, setting it to a logical "reset =
> true"
> level. This maps to the hardware 0V output level, as the signal is
> active-low. To achieve this, define the reset GPIO as active low in
> DT,
> and the GPIO framework will invert the signal for you. You should
> then
> call
> 
> gpiod_set_value_cansleep(gc08a3->reset_gpio, 1);
> 
> in the driver when you want to assert reset (set it to 0V), and
> 
> gpiod_set_value_cansleep(gc08a3->reset_gpio, 0);
> 
> when you want to deassert it (set it to 3.3V, or whatever the I/O
> voltage for the signal is).
> 
> This way all driver use logical states, and the inversion is handled
> in
> DT.
> 

Sensor power sequence as below:
                      ------------------
                     | | |
                     | | | 
dvdd/avdd/dovdd  --------
                               ---------
                              |
                              |
reset-pin        -------------

In order to match this power sequece, "reset-pin" contrl flow is below:
1. config the "reset-pin" is "active-high" in DTS:
    reset-gpios = <&pio 19 GPIO_ACTIVE_HIGH>;

2. image sensor driver probe function:
gc08a3->reset_gpio = devm_gpiod_get(dev, "reset",
GPIOD_OUT_LOW);  //init "reset-pin" is low

3. image sensor driver power_on function:
gpiod_set_value_cansleep(gc08a3->reset_gpio, 1); //pull "reset-pin"
high 

so, the expect state of "reset-pin" is from low to high.
If I am wrong, please correct me.

> > > > +usleep_range(GC08A3_MIN_SLEEP_US, GC08A3_MAX_SLEEP_US);
> > > > +
> > > > +return 0;
> > > > +}
> 
> [snip]
> 
> -- 
> Regards,
> 
> Laurent Pinchart