Re: [PATCH v5 1/2] dt-bindings: i2c: Add Synopsys DWC_i2c controller

[Aniket Limaye <a-limaye@ti.com>]

On 11/11/26 18:54, Mark Brown wrote:
> On Wed, Nov 11, 2026 at 09:41:40AM +0100, Krzysztof Kozlowski wrote:
>> On Wed, Nov 11, 2026 at 12:05:15AM +0000, Mark Brown wrote:
> 
>>> I still think we should have a fallback compatible here, while we can't
>>> discover the FIFO depths all the uses have a programmed trigger and we
>>> know the minimum depth configurable in the IP so we can fall back to
>>> using that.  This would be useful for distro kernels, it's one less
>>> thing that forces using a kernel with specific SoC support.
> 
>> If the driver does not match on such generic compatible - and that's my
>> impression from commit msg -  then it is pretty useless.
> 
> The driver can match on a generic compatible, it just doesn't right now.
> It's getting the FIFO depth from the compatible but as I observe above
> the minimum FIFO depth is known so we can just use that as the fallback,
> we program the trigger points for the FIFO so it doesn't matter if there
> is more space than we're using.

So if I understand it correctly,
1. you'd rather the driver have a generic compatible such that we can 
have distro kernels not requiring specific SOC support for this driver.
2. AND it is possible to have a *sane* fallback by using the IP's 
generic minimum fifo depth. The DWC_i2c manual specifies 
IC_TX_BUFFER_DEPTH and IC_RX_BUFFER_DEPTH as 2..1024, so using depth of 
2 as a fallback would be functional on any integration, just slower.

Krzysztof,

What are your thoughts on having a generic *fallback* compatible 
"snps,dwc-adv-i2c" , used after a SoC-specific one, i.e.
compatible = "ti,tda54-i2c", "snps,dwc-adv-i2c";

The driver would match both. "ti,tda54-i2c" keeps its real 32/32 FIFO 
depths, and the fallback uses 2/2.

Thanks,
Aniket