From: Tomasz Figa <tfiga@chromium.org>
To: Dongchun Zhu <dongchun.zhu@mediatek.com>
Cc: "Sakari Ailus" <sakari.ailus@linux.intel.com>,
"Rob Herring" <robh@kernel.org>,
"Linus Walleij" <linus.walleij@linaro.org>,
"Bartosz Golaszewski" <bgolaszewski@baylibre.com>,
"Mauro Carvalho Chehab" <mchehab@kernel.org>,
"Andy Shevchenko" <andriy.shevchenko@linux.intel.com>,
"Mark Rutland" <mark.rutland@arm.com>,
"Nicolas Boichat" <drinkcat@chromium.org>,
"Matthias Brugger" <matthias.bgg@gmail.com>,
"Cao Bing Bu" <bingbu.cao@intel.com>,
srv_heupstream <srv_heupstream@mediatek.com>,
"moderated list:ARM/Mediatek SoC support"
<linux-mediatek@lists.infradead.org>,
"moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE"
<linux-arm-kernel@lists.infradead.org>,
"Sj Huang" <sj.huang@mediatek.com>,
"Linux Media Mailing List" <linux-media@vger.kernel.org>,
linux-devicetree <devicetree@vger.kernel.org>,
"Louis Kuo" <louis.kuo@mediatek.com>,
"Shengnan Wang (王圣男)" <shengnan.wang@mediatek.com>
Subject: Re: [V9, 1/2] media: dt-bindings: media: i2c: Document OV02A10 bindings
Date: Fri, 29 May 2020 15:43:30 +0200 [thread overview]
Message-ID: <CAAFQd5AuHDpQN8xZsWgnAt6m2reAYJbs9nBp0+mBo7_FS81LbQ@mail.gmail.com> (raw)
In-Reply-To: <1590653082.8804.517.camel@mhfsdcap03>
On Thu, May 28, 2020 at 10:06 AM Dongchun Zhu <dongchun.zhu@mediatek.com> wrote:
>
> Hi Sakari,
>
> On Thu, 2020-05-28 at 10:23 +0300, Sakari Ailus wrote:
> > Hi Dongchun,
> >
> > On Thu, May 28, 2020 at 11:34:42AM +0800, Dongchun Zhu wrote:
> > > Hi Sakari, Rob,
> > >
> > > On Thu, 2020-05-28 at 00:16 +0300, Sakari Ailus wrote:
> > > > Hi Rob, Dongchun,
> > > >
> > > > On Wed, May 27, 2020 at 09:27:22AM -0600, Rob Herring wrote:
> > > > > > > > + properties:
> > > > > > > > + endpoint:
> > > > > > > > + type: object
> > > > > > > > + additionalProperties: false
> > > > > > > > +
> > > > > > > > + properties:
> > > > > >
> > > > > > Actually I wonder whether we need to declare 'clock-lanes' here?
> > > > >
> > > > > Yes, if you are using it.
> > > >
> > > > Dongchun, can you confirm the chip has a single data and a single clock
> > > > lane and that it does not support lane reordering?
> > > >
> > >
> > > From the datasheet, 'MIPI inside the OV02A10 provides one single
> > > uni-directional clock lane and one bi-directional data lane solution for
> > > communication links between components inside a mobile device.
> > > The data lane has full support for HS(uni-directional) and
> > > LP(bi-directional) data transfer mode.'
> > >
> > > The sensor doesn't support lane reordering, so 'clock-lanes' property
> > > would not be added in next release.
> > >
> > > > So if there's nothing to convey to the driver, also the data-lanes should
> > > > be removed IMO.
> > > >
> > >
> > > However, 'data-lanes' property may still be required.
> > > It is known that either data-lanes or clock-lanes is an array of
> > > physical data lane indexes. Position of an entry determines the logical
> > > lane number, while the value of an entry indicates physical lane, e.g.,
> > > for 1-lane MIPI CSI-2 bus we could have "data-lanes = <1>;", assuming
> > > the clock lane is on hardware lane 0.
> > >
> > > As mentioned earlier, the OV02A10 sensor supports only 1C1D and does not
> > > support lane reordering, so here we shall use 'data-lanes = <1>' as
> > > there is only a clock lane for OV02A10.
> > >
> > > Reminder:
> > > If 'data-lanes' property is not present, the driver would assume
> > > four-lane operation. This means for one-lane or two-lane operation, this
> > > property must be present and set to the right physical lane indexes.
> > > If the hardware does not support lane reordering, monotonically
> > > incremented values shall be used from 0 or 1 onwards, depending on
> > > whether or not there is also a clock lane.
> >
> > How can the driver use four lanes, considering the device only supports a
> > single lane??
> >
>
> I understood your meaning.
> If we omit the property 'data-lanes', the sensor should work still.
> But then what's the meaning of the existence of 'data-lanes'?
> If this property 'data-lanes' is always optional, then why dt-bindings
> provide the interface?
>
> In the meantime, if omitting 'data-lanes' for one sensor(transmitter)
> that has only one physical data lane, MIPI receiver(e.g., MIPI CSI-2)
> shall enable four-lane configuration, which may increase consumption of
> both power and resource in the process of IIC communication.
Wouldn't the receiver still have the data-lanes property under its
endpoint node, telling it how many lanes and in which order should be
used?
Best regards,
Tomasz
next prev parent reply other threads:[~2020-05-29 13:52 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-23 8:41 [V9, 0/2] media: i2c: Add support for OV02A10 sensor Dongchun Zhu
2020-05-23 8:41 ` [V9, 1/2] media: dt-bindings: media: i2c: Document OV02A10 bindings Dongchun Zhu
2020-05-26 18:28 ` Rob Herring
2020-05-27 8:49 ` Dongchun Zhu
2020-05-27 15:27 ` Rob Herring
2020-05-27 21:16 ` Sakari Ailus
2020-05-28 3:34 ` Dongchun Zhu
2020-05-28 7:23 ` Sakari Ailus
2020-05-28 8:04 ` Dongchun Zhu
2020-05-29 13:43 ` Tomasz Figa [this message]
2020-06-01 2:33 ` Dongchun Zhu
2020-06-01 18:18 ` Tomasz Figa
2020-06-02 6:15 ` Dongchun Zhu
2020-06-02 9:56 ` Sakari Ailus
2020-06-04 2:20 ` Dongchun Zhu
2020-06-02 9:53 ` Sakari Ailus
2020-05-28 5:53 ` Dongchun Zhu
2020-05-23 8:41 ` [V9, 2/2] media: i2c: ov02a10: Add OV02A10 image sensor driver Dongchun Zhu
2020-06-04 2:14 ` Dongchun Zhu
2020-06-04 9:26 ` Sakari Ailus
2020-06-04 18:05 ` Tomasz Figa
2020-06-05 3:19 ` Dongchun Zhu
2020-06-10 19:44 ` Tomasz Figa
2020-06-11 9:53 ` Sakari Ailus
2020-06-11 9:57 ` Tomasz Figa
2020-06-11 10:03 ` Sakari Ailus
2020-06-12 11:01 ` Dongchun Zhu
2020-06-12 10:46 ` Dongchun Zhu
2020-06-12 18:39 ` Tomasz Figa
2020-06-15 5:54 ` Dongchun Zhu
2020-06-15 12:44 ` Tomasz Figa
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