Re: [PATCH v26 2/4] dt-bindings: i2c: ast2600-i2c.yaml: Add global-regs and transfer-mode properties

[Jeremy Kerr <jk@codeconstruct.com.au>]

Hi Ryan,

> Your understanding is correct; the byte and buffer mode is mostly the
> same. And also mode should be decided before xfer, due to the
> controller/target both use the same xfer mode, not decide by transfer
> time. The original my submit is only buffer mode and dma mode, and use
> only one Boolean property, aspeed,i2c-dma-enabled, but someone suggest
> add byte mode select, so I start to add at v17. I can drop the byte
> mode, if this is confused.
> 
> byte mode request:
> https://lore.kernel.org/all/010e55e9-d58b-444c-ab57-
> ddf8c75f2390@gmail.com/

OK, that sounds like more driver configuration than hardware description
though.

> > Ryan: I think this gives us a much cleaner approach to the binding.
> Thanks the feedback, do you mean, just one boolean property for mode
> selection,
> Am I right?

It's less about "mode selection" (which is a driver implementation
consideration) and more about "hardware capability", which I think the
boolean property better represents.

The driver implementation could do whatever it likes with the
information about whether a DMA channel is allocated (and select a
suitable mode depending on that, and/or other runtime data).

This property only seems to be applicable to 2600 though, as there is no
need for it on 2700, if all controllers are DMA-capable.

Cheers,


Jeremy