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Message-ID: <6be0e8d2e899bcc9505ec62ba59290f97a07d812.camel@mediatek.com>
Date: Tue, 27 Feb 2024 01:36:19 +0000
From: Zhi Mao (毛智) <zhi.mao@...iatek.com>
To: "sakari.ailus@...ux.intel.com" <sakari.ailus@...ux.intel.com>
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Subject: Re: [PATCH v4 2/2] media: i2c: Add GC08A3 image sensor driver
Hi Sakari,
Thanks for your feedback.
On Wed, 2024-02-21 at 07:43 +0000, sakari.ailus@...ux.intel.com wrote:
>
> External email : Please do not click links or open attachments until
> you have verified the sender or the content.
> Hi Zhi,
>
> On Wed, Feb 21, 2024 at 02:37:27AM +0000, Zhi Mao (毛智) wrote:
> > Hi Laurent & sakari,
> >
> > Thanks for your feedback.
> >
> > On Tue, 2024-02-20 at 07:25 +0000, sakari.ailus@...ux.intel.com
> 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 05:45:54AM +0000, Zhi Mao (毛智) wrote:
> > > > 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.
> > >
> > >
> > > From Documentation/driver-api/gpio/consumer.rst:
> > >
> > > As a consumer should not have to care about the physical line
> > > level, all of the gpiod_set_value_xxx() or
> > > gpiod_set_array_value_xxx() functions operate with the *logical*
> > > value. With this they take the active low property into account.
> > > This means that they check whether the GPIO is configured to be
> > > active low, and if so, they manipulate the passed value before
> the
> > > physical line level is driven.
> > >
> > > I.e. when you want to enable reset, you set the value to 1 in the
> > > driver. I
> > > think you're now setting the value to 0 in that case. The
> opposite
> > > for
> > > disabling it of course.
> > >
> > After checking "Documentation/driver-api/gpio/consumer.rst":
> > To summarize::
> > Function (example) line
> property physical
> > line
> > ...
> > gpiod_set_value(desc, 1); default (active high) high
> > gpiod_set_value(desc, 0); active low high
> > ...
> >
> >
> > From my understanding, it seems that "reset-pin" is using the
> > following(active_high) case in current code:
> > "gpiod_set_value(desc, 1); default (active high) high"
> >
> > Do you mean, we should use the "active_low" case:
> > "gpiod_set_value(desc, 0); active low high"
> > Code should be changed as below:
> > 1. config the "reset-pin" is "active-low" in DTS:
> > - reset-gpios = <&pio 19 GPIO_ACTIVE_LOW>
> > 2. image sensor driver power_on function:
> > - gpiod_set_value_cansleep(gc08a3->reset_gpio, 0); //pull high
> > Is that so?
>
> Correct.
>
fixed in patch:v6
> --
> Regards,
>
> Sakari Ailus
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