Hi Ryan, > --- a/Documentation/devicetree/bindings/i2c/aspeed,i2c.yaml > +++ b/Documentation/devicetree/bindings/i2c/aspeed,i2c.yaml > @@ -49,6 +49,25 @@ properties: > description: > states that there is another master active on this bus > > + aspeed,timeout: > + type: boolean > + description: I2C bus timeout enable for master/slave mode > + > + aspeed,xfer-mode: > + description: | > + I2C bus transfer mode selection. > + - "byte": I2C bus byte transfer mode. > + - "buffered": I2C bus buffer register transfer mode. > + - "dma": I2C bus dma transfer mode (default) > + items: > + enum: [byte, buffered, dma] > + maxItems: 1 > + $ref: /schemas/types.yaml#/definitions/non-unique-string-array There are still unresolved questions about this xfer-mode property from previous submissions of this binding. We don't yet have a justification on why the mode configuration is needed in the device tree rather than something that is specified in a driver implementation. By now, I think we well understand what the modes are, and how a driver implementation might configure them, but none of that has (so far) provided sufficient rationale on why this belongs in the device tree. The previous threads had a couple of pending discussions, following up on those here: A) You mentioned in [1] that the DMA controller is shared between all i3c devices, does that have any consequence on which modes individual devices might want to choose? B) You implied in [2] that the different transfer modes might be related to whether there are other masters present on the bus, but the logic behind that is not clear. C) In [3] you mentioned that there might be some DRAM savings by using a particular mode. and, most importantly: D) unanswered from [4] and [5]: what are the hardware-specified reasons why a DT author would chose one mode over another? If you can write this out in some format like: - in hardware situation X, you should use DMA mode - in hardware situation Y, you should use byte mode - [...] that might help us to understand where this configuration belongs, or what a reasonable DT representation should look like, or even if existing DT schema can already provide the information required to decide. Cheers, Jeremy [1]: https://lists.ozlabs.org/pipermail/linux-aspeed/2023-February/009876.html [2]: https://lists.ozlabs.org/pipermail/linux-aspeed/2023-February/009892.html [3]: https://lists.ozlabs.org/pipermail/linux-aspeed/2023-February/009880.html [4]: https://lists.ozlabs.org/pipermail/linux-aspeed/2023-February/009871.html [5]: https://lists.ozlabs.org/pipermail/linux-aspeed/2023-February/009884.html
