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Wed, 03 Jun 2020 18:24:16 -0800 Received: from MTKMBS31N2.mediatek.inc (172.27.4.87) by MTKMBS62N2.mediatek.inc (172.29.193.42) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Wed, 3 Jun 2020 19:22:11 -0700 Received: from MTKCAS36.mediatek.inc (172.27.4.186) by MTKMBS31N2.mediatek.inc (172.27.4.87) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Thu, 4 Jun 2020 10:22:06 +0800 Received: from [10.17.3.153] (10.17.3.153) by MTKCAS36.mediatek.inc (172.27.4.170) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Thu, 4 Jun 2020 10:22:06 +0800 Message-ID: <1591237204.8804.550.camel@mhfsdcap03> Subject: Re: [V9, 1/2] media: dt-bindings: media: i2c: Document OV02A10 bindings From: Dongchun Zhu To: Sakari Ailus Date: Thu, 4 Jun 2020 10:20:04 +0800 In-Reply-To: <20200602095654.GD29325@paasikivi.fi.intel.com> References: <1590569355.8804.448.camel@mhfsdcap03> <20200527211628.GT7618@paasikivi.fi.intel.com> <1590636882.8804.474.camel@mhfsdcap03> <20200528072332.GW7618@paasikivi.fi.intel.com> <1590653082.8804.517.camel@mhfsdcap03> <1590978816.8804.523.camel@mhfsdcap03> <1591078501.8804.539.camel@mhfsdcap03> <20200602095654.GD29325@paasikivi.fi.intel.com> X-Mailer: Evolution 3.10.4-0ubuntu2 MIME-Version: 1.0 X-TM-SNTS-SMTP: FC5061473807FB5FAEA43220556C92A855E1739EDF7A0C65A336E13C0824ECB32000:8 X-MTK: N X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200603_192428_323244_2E671219 X-CRM114-Status: GOOD ( 33.36 ) X-BeenThere: linux-mediatek@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Rob Herring , Andy Shevchenko , srv_heupstream , linux-devicetree , Linus Walleij , Shengnan Wang =?UTF-8?Q?=28=E7=8E=8B=E5=9C=A3=E7=94=B7=29?= , Tomasz Figa , Bartosz Golaszewski , Sj Huang , Nicolas Boichat , "moderated list:ARM/Mediatek SoC support" , dongchun.zhu@mediatek.com, Louis Kuo , Matthias Brugger , Cao Bing Bu , Mauro Carvalho Chehab , "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" , Linux Media Mailing List Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-mediatek" Errors-To: linux-mediatek-bounces+linux-mediatek=archiver.kernel.org@lists.infradead.org Hi Sakari, On Tue, 2020-06-02 at 12:56 +0300, Sakari Ailus wrote: > Hi Dongchun, > > On Tue, Jun 02, 2020 at 02:15:01PM +0800, Dongchun Zhu wrote: > > Hi Tomasz, Sakari, > > > > On Mon, 2020-06-01 at 20:18 +0200, Tomasz Figa wrote: > > > On Mon, Jun 1, 2020 at 4:35 AM Dongchun Zhu wrote: > > > > > > > > Hi Tomasz, > > > > > > > > On Fri, 2020-05-29 at 15:43 +0200, Tomasz Figa wrote: > > > > > On Thu, May 28, 2020 at 10:06 AM Dongchun Zhu 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? > > > > > > > > > > > > > The MIPI receiver(RX) shall use > > > > v4l2_async_notifier_add_fwnode_remote_subdev() API to parse the property > > > > "data-lanes" under sensor output port. > > > > > > That's not true. The MIPI receiver driver parses its own port node > > > corresponding to the sensor. Also quoting the documentation [1]: > > > > > > "An endpoint subnode of a device contains all properties needed for > > > _configuration of this device_ for data exchange with other device. In most > > > cases properties at the peer 'endpoint' nodes will be identical, however they > > > might need to be different when there is any signal modifications on the bus > > > between two devices, e.g. there are logic signal inverters on the lines." > > > > > > In this case, there is such a signal modification if the sensor has a > > > 1-lane bus and the receiver more lines, so the data-lanes properties > > > would be different on both sides. > > > > > > [1] https://elixir.bootlin.com/linux/v5.7/source/Documentation/devicetree/bindings/media/video-interfaces.txt > > > > > > > Sorry for the misunderstanding. > > After doing some experiments about the data-lanes property under sensor > > i2c node, we found the API > > v4l2_async_notifier_add_fwnode_remote_subdev() that MIPI receiver driver > > used indeed parses the data-lanes under its own port node. > > > > Sorry make a mistake for the use case of sensor data-lanes previously. > > Now We may encounter one new question for this patch. > > In practice we haven't used the data-lanes under sensor i2c node > > anywhere, if sensor driver itself doesn't parse that. > > > > But there is still one reason to keep the exactly right data-lanes in > > DT. That is, the data-lanes under sensor i2c node could be used as a > > reference for MIPI receiver driver. > > Just as Tomasz said, 'The MIPI receiver driver parses its own port node > > corresponding to the sensor'. > > > > Sakari, Tomasz, what's your opinions about the present of data-lanes > > under sensor node or not? > > The receiver driver doesn't parse the properties in the sensor > (transmitter) device's endpoint. If that property provides no information > to the receiver, as is the case here, it should be omitted. > Understood. Fixed in next release. _______________________________________________ Linux-mediatek mailing list Linux-mediatek@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-mediatek