Hi Tomasz, Sakari, Thanks for digging into the imperfections. On Mon, 2020-08-31 at 19:06 +0300, Sakari Ailus wrote: > Hi Tomasz, > > Thanks for dressing this into words. > > On Mon, Aug 31, 2020 at 01:44:27PM +0200, Tomasz Figa wrote: > > Hi Dongchun, > > > > On Fri, Jul 10, 2020 at 12:19 PM Dongchun Zhu <dongchun.zhu@xxxxxxxxxxxx> wrote: > > > > > > Add YAML device tree binding for OV02A10 CMOS image sensor, > > > and the relevant MAINTAINERS entries. > > > > > > Reviewed-by: Tomasz Figa <tfiga@xxxxxxxxxxxx> > > > Reviewed-by: Rob Herring <robh@xxxxxxxxxx> > > > Signed-off-by: Dongchun Zhu <dongchun.zhu@xxxxxxxxxxxx> > > > --- > > > .../bindings/media/i2c/ovti,ov02a10.yaml | 172 +++++++++++++++++++++ > > > MAINTAINERS | 7 + > > > 2 files changed, 179 insertions(+) > > > create mode 100644 Documentation/devicetree/bindings/media/i2c/ovti,ov02a10.yaml > > > > > > diff --git a/Documentation/devicetree/bindings/media/i2c/ovti,ov02a10.yaml b/Documentation/devicetree/bindings/media/i2c/ovti,ov02a10.yaml > > > new file mode 100644 > > > index 0000000..3a916cc > > > --- /dev/null > > > +++ b/Documentation/devicetree/bindings/media/i2c/ovti,ov02a10.yaml > > > @@ -0,0 +1,172 @@ > > > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) > > > +# Copyright (c) 2020 MediaTek Inc. > > > +%YAML 1.2 > > > +--- > > > +$id: http://devicetree.org/schemas/media/i2c/ovti,ov02a10.yaml# > > > +$schema: http://devicetree.org/meta-schemas/core.yaml# > > > + > > > +title: Omnivision OV02A10 CMOS Sensor Device Tree Bindings > > > + > > > +maintainers: > > > + - Dongchun Zhu <dongchun.zhu@xxxxxxxxxxxx> > > > + > > > +description: |- > > > + The Omnivision OV02A10 is a low-cost, high performance, 1/5-inch, 2 megapixel > > > + image sensor, which is the latest production derived from Omnivision's CMOS > > > + image sensor technology. Ihis chip supports high frame rate speeds up to 30fps > > > + @ 1600x1200 (UXGA) resolution transferred over a 1-lane MIPI interface. The > > > + sensor output is available via CSI-2 serial data output. > > > + > > > +properties: > > > + compatible: > > > + const: ovti,ov02a10 > > > + > > > + reg: > > > + maxItems: 1 > > > + > > > + clocks: > > > + items: > > > + - description: top mux camtg clock > > > + - description: divider clock > > > + > > > + clock-names: > > > + items: > > > + - const: eclk > > > + - const: freq_mux > > > > Why do we have two clocks here? Looking at the example suggests that > > they may be the clocks of the SoC that the integration was done with. > > However, the binding must only define the aspects of the particular > > device, i.e. this sensor. > > > > I suppose we should only have "eclk" here and it should be described > > as "external clock for the sensor". > > I cannot agree with you more, it would be fixed in next release. > > > + > > > + clock-frequency: > > > + description: > > > + Frequency of the eclk clock in Hertz. > > > > nit: maybe Hz? > > Both shall be okay, let's use Hz instead, which seems to be more simple. > > > + > > > + dovdd-supply: > > > + description: > > > + Definition of the regulator used as Digital I/O voltage supply. > > > + > > > + avdd-supply: > > > + description: > > > + Definition of the regulator used as Analog voltage supply. > > > + > > > + dvdd-supply: > > > + description: > > > + Definition of the regulator used as Digital core voltage supply. > > > + > > > + powerdown-gpios: > > > + description: > > > + Must be the device tree identifier of the GPIO connected to the > > > + PD_PAD pin. This pin is used to place the OV02A10 into standby mode > > > + or shutdown mode. As the line needs to be high for the powerdown mode > > > + to be active, it should be marked GPIO_ACTIVE_HIGH. > > > + maxItems: 1 > > > + > > > + reset-gpios: > > > + description: > > > + Must be the device tree identifier of the GPIO connected to the > > > + RST_PD pin. If specified, it will be asserted during driver probe. > > > + As the line needs to be low for the reset to be active, it should be > > > + marked GPIO_ACTIVE_LOW. > > > + maxItems: 1 > > > + > > > + rotation: > > > + description: > > > + Definition of the sensor's placement. > > > + allOf: > > > + - $ref: "/schemas/types.yaml#/definitions/uint32" > > > + - enum: > > > + - 0 # Sensor Mounted Upright > > > + - 180 # Sensor Mounted Upside Down > > > + default: 0 > > > + > > > + ovti,mipi-tx-speed: > > > + description: > > > + Indication of MIPI transmission speed select, which is to control D-PHY > > > + timing setting by adjusting MIPI clock voltage to improve the clock > > > + driver capability. > > > > The description says that the value adjusts "MIPI clock voltage". > > Should the property be renamed to "ovti,mipi-clock-voltage"? > > Sure, mipi-clock-voltage seems more clear, perfect naming :-) > > > + allOf: > > > + - $ref: "/schemas/types.yaml#/definitions/uint32" > > > + - enum: > > > + - 0 # 20MHz - 30MHz > > > + - 1 # 30MHz - 50MHz > > > + - 2 # 50MHz - 75MHz > > > + - 3 # 75MHz - 100MHz > > > + - 4 # 100MHz - 130MHz > > > + default: 3 > > > + > > > > I've discussed this on IRC with Sakari. It sounds like this works as > > is for us because the driver currently only supports 1 mode, always > > running the link at 390 MHz. This won't scale if one intends to add > > more modes, because DT can't be expected to be updated when the driver > > changes. The two are expected to be separate and backwards compatible. > > > > I think we could model this in DT as an array of <link speed, clock > > voltage> pairs. Similarly to the OPP bindings [1]. An example to have > > all link speeds up to 390 MHz use the value 4: > > > > ovti,mipi-clock-voltages = < > > /* KHz clock voltage unit */ > > 390000 4 > > >; > > > > if one wants to select different voltage for different link, they > > could do so as well. With the example below, the driver should > > configure "3" for link frequencies <= 150 MHz and "4" for > 150 MHz <= > > 390 MHz. Link frequencies > 390 MHz should be disallowed. > > > > ovti,mipi-clock-voltages = < > > /* KHz clock voltage unit */ > > 150000 3 > > 390000 4 > > >; > > > > What do you think? > So now we define the MIPI clock voltage (unit) as one function of link frequency? For current sensor mode (1600x1200, 390MHz link frequency), we then shall always use the value 4 to configure the MIPI transmission speed selection (P1:0xA1). Am I correct in thinking that? > One more note on my proposal: use the index of the link frequency to access > the ovti,mipi-clock-voltages array. That should be more simple for the > driver, as the driver is expected to use only link frequencies listed in DT > bindings anyway. > Good idea! That's exactly what I mean. Just submitted one draft change to handle the new property in DT. @Sakari @Tomasz please help to review it. https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/2387980/1/drivers/media/i2c/ov02a10.c#883
