Re: [PATCH v2 3/5] dt-bindings: spi: add stm32f7-spi compatible

[Ben Wolsieffer]

Hi Conor,

On Fri, Nov 03, 2023 at 12:50:53PM +0000, Conor Dooley wrote:
> On Thu, Nov 02, 2023 at 03:37:20PM -0400, Ben Wolsieffer wrote:
> A wider range of supported word sizes and some additional buffers,
> implies that the F4 could be used as a fallback compatible. Does the
> register map change incompatibly in the process of widening the FIFOs or
> something like that?

Yes, the F4 has a single bit to select 8 or 16 bit word size, while the
F7 uses four bits to select an arbitrary word size from 4 to 16 bits.
This series supports the packing mode, to allow sending two <=8 bit
words with a single write to the FIFO, but even if we didn't want to
support this feature, the F7 would require setting the FRXTH bit (not
present in the F4) when using <=8 bit word sizes.

> 
> Cheers,
> Conor.