Re: [PATCH v2 5/9] dt-bindings: display: bridge: Add ITE IT6263 LVDS to HDMI converter

[Dmitry Baryshkov]

On Mon, Oct 14, 2024 at 08:09:44AM +0000, Biju Das wrote:
> Hi Dmitry,
> 
> > -----Original Message-----
> > From: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> > Sent: Monday, October 14, 2024 9:04 AM
> > Subject: Re: [PATCH v2 5/9] dt-bindings: display: bridge: Add ITE IT6263 LVDS to HDMI converter
> > 
> > On Mon, Oct 14, 2024 at 07:39:16AM +0000, Biju Das wrote:
> > > Hi Liu and Dmitry,
> > >
> > > > -----Original Message-----
> > > > From: Liu Ying <victor.liu@xxxxxxx>
> > > > Sent: Monday, October 14, 2024 6:34 AM
> > > > Subject: Re: [PATCH v2 5/9] dt-bindings: display: bridge: Add ITE
> > > > IT6263 LVDS to HDMI converter
> > > >
> > > > On 10/14/2024, Dmitry Baryshkov wrote:
> > > > > On Sat, Oct 12, 2024 at 05:14:13PM +0800, Liu Ying wrote:
> > > > >> On 10/12/2024, Dmitry Baryshkov wrote:
> > > > >>> On Sat, Oct 12, 2024 at 03:35:39PM +0800, Liu Ying wrote:
> > > > >>>> Document ITE IT6263 LVDS to HDMI converter.
> > > > >>>>
> > > > >>>> Product link:
> > > > >>>> https://www.ite.com.tw/en/product/cate1/IT6263
> > > > >>>>
> > > > >>>> Signed-off-by: Liu Ying <victor.liu@xxxxxxx>
> > > > >>>> ---
> > > > >>>> v2:
> > > > >>>> * Document number of LVDS link data lanes.  (Biju)
> > > > >>>> * Simplify ports property by dropping "oneOf".  (Rob)
> > > > >>>>
> > > > >>>>  .../bindings/display/bridge/ite,it6263.yaml   | 276 ++++++++++++++++++
> > > > >>>>  1 file changed, 276 insertions(+)  create mode 100644
> > > > >>>> Documentation/devicetree/bindings/display/bridge/ite,it6263.yam
> > > > >>>> l
> > > > >>>>
> > > > >>>> diff --git
> > > > >>>> a/Documentation/devicetree/bindings/display/bridge/ite,it6263.y
> > > > >>>> aml
> > > > >>>> b/Documentation/devicetree/bindings/display/bridge/ite,it6263.y
> > > > >>>> aml
> > > > >>>> new file mode 100644
> > > > >>>> index 000000000000..bc2bbec07623
> > > > >>>> --- /dev/null
> > > > >>>> +++ b/Documentation/devicetree/bindings/display/bridge/ite,it62
> > > > >>>> +++ 63.y
> > > > >>>> +++ aml
> > > > >>>> @@ -0,0 +1,276 @@
> > > > >>>> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > > > >>>> +%YAML
> > > > >>>> +1.2
> > > > >>>> +---
> > > > >>>> +$id:
> > > > >>>> +http://devicetree.org/schemas/display/bridge/ite,it6263.yaml#
> > > > >>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > > >>>> +
> > > > >>>> +title: ITE IT6263 LVDS to HDMI converter
> > > > >>>> +
> > > > >>>> +maintainers:
> > > > >>>> +  - Liu Ying <victor.liu@xxxxxxx>
> > > > >>>> +
> > > > >>>> +description: |
> > > > >>>> +  The IT6263 is a high-performance single-chip
> > > > >>>> +De-SSC(De-Spread
> > > > >>>> +Spectrum) LVDS
> > > > >>>> +  to HDMI converter.  Combined with LVDS receiver and HDMI
> > > > >>>> +1.4a transmitter,
> > > > >>>> +  the IT6263 supports LVDS input and HDMI 1.4 output by conversion function.
> > > > >>>> +  The built-in LVDS receiver can support single-link and
> > > > >>>> +dual-link LVDS inputs,
> > > > >>>> +  and the built-in HDMI transmitter is fully compliant with
> > > > >>>> +HDMI 1.4a/3D, HDCP
> > > > >>>> +  1.2 and backward compatible with DVI 1.0 specification.
> > > > >>>> +
> > > > >>>> +  The IT6263 also encodes and transmits up to 8 channels of
> > > > >>>> + I2S digital audio,  with sampling rate up to 192KHz and
> > > > >>>> + sample size up to 24 bits. In addition,  an S/PDIF input port
> > > > >>>> + takes in compressed audio of up to 192KHz
> > > > frame rate.
> > > > >>>> +
> > > > >>>> +  The newly supported High-Bit Rate(HBR) audio by HDMI
> > > > >>>> + specifications v1.3 is  provided by the IT6263 in two interfaces:
> > > > >>>> + the four I2S input ports or the  S/PDIF input port.  With
> > > > >>>> + both interfaces the highest possible HBR frame rate  is supported at up to 768KHz.
> > > > >>>> +
> > > > >>>> +properties:
> > > > >>>
> > > > >>> No LVDS data-mapping support?
> > > > >>
> > > > >> It is enough to document number of LVDS link data lanes because
> > > > >> OS should be able to determine the data-mapping by looking at the
> > > > >> number and the data-mapping capability of the other side of the LVDS link.
> > > > >
> > > > > From what I can see, data-mapping is specified on the consumer
> > > > > sink side of the LVDS link. This means it should go to the bridge's device node.
> > > >
> > > > Then, I won't define data-lanes, because data-mapping implies it,
> > > > e.g., jeida-24 implies data lanes 0/1/2/3, see lvds-data-mapping.yaml.
> > > >
> > > > Please let me know which one you prefer.
> > >
> > > Assume a top level use case where a user changes the format from JEDAI
> > > to VESA using On screen display or modetest(if some one adds support
> > > for lvds-mapping) then setting of the lvds data mapping should be dynamic.
> > >
> > > Maybe for initial version hardcode with JEDAI or VESA as default and
> > > provide a way to override the host driver and bridge with requested lvds-data mapping dynamically
> > later??
> > 
> > The ite,lvds-link-num-data-lanes property should be removed, it is not standard. I foresee two ways to
> > specify the number of lanes used: either the data-lanes property or the data-mapping property. Granted
> > that data-mapping replaces the data-lanes functionality for LVDS links, I think it's better to use it
> > from the start.
> > 
> > Frankly speaking, what is the usecase for specifying the data mapping dynamically? What kind of uAPI
> > do you have in mind and what is the usecase for it?
> 
> It simple just want to change from VESA to JEDAI, how do you change it with existing DRM framework?

Why do you want to change it on the fly?

> Currently I see LVDS panel driver use drm_of_lvds_get_data_mapping(bus_node) to get this info.
> IT6263 bridge device can use that API to get that info.
> 
> Some vendors use VESA as default LVDS data mapping whereas some others use JEDAI.

I think this is logical. Bus format is set by the system design
constraints. In theory one can use buf format negotiation for the same
purpose.

> 
> Cheers,
> Biju

-- 
With best wishes
Dmitry