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

[Dmitry Baryshkov]

On Mon, Oct 14, 2024 at 11:25:00AM +0000, Biju Das wrote:
> Hi Dmitry,
> 
> > -----Original Message-----
> > From: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>
> > Sent: Monday, October 14, 2024 12:16 PM
> > Subject: Re: [PATCH v2 5/9] dt-bindings: display: bridge: Add ITE IT6263 LVDS to HDMI converter
> > 
> > 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,it62
> > > > > > >>>> 63.y
> > > > > > >>>> aml
> > > > > > >>>> b/Documentation/devicetree/bindings/display/bridge/ite,it62
> > > > > > >>>> 63.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
> > > > > > >>>> +---
> > > > > > >>>> +$id:
> > > > > > >>>> +http://devicetree.org/schemas/display/bridge/ite,it6263.ya
> > > > > > >>>> +ml#
> > > > > > >>>> +$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?
> 
> It will reduce validation effort for LVDS and bridge driver for testing various bus formats.
> 
> By allowing on the fly, with single dtb, we can validate various bus formats.
> Otherwise each dtb for testing each bus format.

I see your point, but I don't think it falls into the uAPI area. Feel
free to propose a mechanism to change data-mapping through the debugfs
though. I think that's the best possible option.

> 
> From a product perspective, this use case is not valid.
> 
> Cheers,
> Biju
> 

-- 
With best wishes
Dmitry