Subject: Re: [PATCH v18 1/3] dt-bindings: i2c: aspeed,i2c.yaml: add
transfer-mode and global-regs properties and update example

On Mon, Sep 15, 2025 at 11:41:31AM +0800, Jeremy Kerr wrote:

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Hi Ryan,

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OK, but the ast2400 and ast2500 I2C peripherals - which this
binding also describes - do not have that facility. Given the 2600
is a distinct peripheral (as discussed on the v16 series), this would seem

to warrant a distinct binding.

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Should this be split out into an ast2600-specific binding, to
reflect that it is different hardware? The reference to the global
registers and transfer modes would then be added only to the

ast2600-i2c-bus binding.

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I agree it would be cleaner to split out a new binding file
specifically for AST2600, for example: `aspeed,ast2600-i2c.yaml` But
also I think `aspeed,i2cv2.yaml` more better name, that compatible
will support next generation such like AST2700 .....

The ship may have already sailed on that one, as you already have the
existing compatible string describing existing hardware.

I would assume that the compatible string should be fixed for an
instance of the specific hardware, but the DT maintainers may be able
to provide some input/precedence on changing an existing binding, if
necessary.

If this does get changed, I would expect that you would need a
corresponding update in the old driver too.

Or, another option may be to keep the current generation ("v2 core
with compat registers") as-is (ie., at ast2600-i2c-bus), and introduce
a new string for the next - where the primary hardware change might be
the removal of compat registers, but it's still new hardware

About the only place we use version numbers (without regret) is when the
version can be traced back to the actual verilog. This is typically only IP
targeted to FPGAs. The reality in SoCs is h/w designers can't help themselves to
not change things. In reality, there are almost always some changes.

Rob

Thanks, I think I will work on new yaml aspeed,ast2600-i2c.yaml for ast2600 i2c driver.
That support global regs, transfer-mode properties.
Then will add ast2700-i2c.yaml for ast2700 i2c.

Ryan.