DSI host controllers these days can be ganged together to drive larger displays. Every SoC vendor supporting this is trying to add their own DT property so that the corresponding drivers can identify that they need to operate in the dual DSI mode. If we use the graph bindings, we don't really need an additional DT property in the DSI host controller to tell it that it's operating in dual-channel mode. It's something that can be inferred
I don't know much about how dual-channel is implemented on anything apart from MSM chipsets, but one thing that seems universal is that the clock driving both the DSI controllers (and corresponding PHYs) should have the same clock source. The DSI instance that drives this clock is generally called the "master", and the other instance the "slave". A "clock-master" DT property has been proposed for the same.
There are some open item(s) that aren't described in the mipi DSI/DCS spec, but we might need to have either as bindings or some sort of DSI flags:
- When sending commands over DSI to peripherals with 2 DSI channels, some peripherals seem to have a requirement that both the DSIs trigger the same command at the same time. Otherwise, the controller on the peripheral goes a bit nuts. Is this common to all peripherals? Or are there devices where we just need to send the DCS/generic commands to the "master" DSI channel?
- When trying to read something back from the panel (a DCS read command followed by a BTA etc.), should both the DSI controllers be listening for data, or only the master?
- Anything else?
The first patch adds some explanation on how to deal with peripherals that do DSI, but have a different control bus. This is something we've already started using, but didn't have properly documented anywhere.
The second patch proposes bindings for DSI hosts/peripherals that implement dual-channel DSI.
Changes in v2: - Incorported Rob's comments.
Archit Taneja (2): dt-bindings: mipi-dsi: Add info about peripherals with non-DSI control bus dt-bindings: mipi-dsi: Add dual-channel DSI related info
.../devicetree/bindings/display/mipi-dsi-bus.txt | 153 +++++++++++++++++++-- 1 file changed, 145 insertions(+), 8 deletions(-)