Re: [PATCH v2 0/5] drm/bridge: sii902x: HDMI-audio support and some fixes

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Jyri,

On Mon, Mar 04, 2019 at 04:29:17PM +0200, Jyri Sarha wrote:
> On 04/03/2019 14:42, Laurent Pinchart wrote:
> > On Wed, Feb 27, 2019 at 11:54:18PM +0200, Jyri Sarha wrote:
> >> Changes since first version:
> >> - Moved reviewed patches to front:
> >>   - drm/bridge: sii902x: add input_bus_flags
> >>   - drm/bridge: sii902x: Set output mode to HDMI or DVI according to EDID
> >>   - drm/bridge: sii902x: pixel clock unit is 10kHz instead of 1kHz
> >> - Added a new fix:
> >>   - drm/bridge: sii902x: Select I2C_MUX
> >> - Applied some review suggestions to
> >>   - drm/bridge: sii902x: Implement HDMI audio support
> >>     - use clock-names property to name mclk
> >>     - move comment describing added mutex to struct sii902x and improve it
> >>     - cleanup sii902x_mute()
> >>     - cleanup sii902x_select_mclk_div()
> >>     - fix condition for checking ENABLE_BIT from i2s_fifo_routing in
> >>       sii902x_audio_codec_init()
> >>
> >> Still to do
> >>
> >> - Agree on i2s wires to HDMI audio fifo routing in dts. 
> >>
> >>   The current scheme is quite straight forward, but there is maybe
> >>   there is even more straight forward solutions like:
> >>
> >>   audio-fifo-enable = <1 1 1 1>;
> >>   audio-i2s-pin-to-fifo = <0 1 2 3>;
> >>
> >>   Meaning that all fifos are enabled and SD0 is routed to fifo 0, SD1
> >>   to fifo 1, etc. I am not sure if the channel swap functionality
> >>   should show in dts binding.
> > 
> > Please forgive my lack of audio knowledge, but it this a system
> > description that should be encoded in DT, or a policy that should be
> > handled purely in software (either fully inside the kernel or with the
> > help of userspace) ?
> 
> This property describes how many i2s wires are connected to sii902x and
> in what order, so I think it belongs to DTS.

That would belong to DT, yes. We have solved a similar problem with
CSI-2 receivers, where the number of data lanes and their mapping can
often be configured. See the definition of the data-lanes property in
Documentation/devicetree/bindings/media/video-interfaces.txt for more
information. How about using similar bindings ? It would also solve
Andrzej's concerns that you don't describe the audio connection in DT.

> One might of course wonder why anybody would put the i2s wires to any
> other order than 0 <-> 0, 1 <-> 1, 2 <-> 2, and 3 <-> 3, but then a
> again I've seen weirder board designs.

It can be useful to simplify signal routing on the board.

-- 
Regards,

Laurent Pinchart
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