Re: [PATCH 4/6] spi: axi-spi-engine: support SPI_MULTI_BUS_MODE_STRIPE

["Nuno Sá" <noname.nuno@gmail.com>]

On Wed, 2025-10-15 at 11:29 -0500, David Lechner wrote:
> On 10/15/25 5:30 AM, Nuno Sá wrote:
> > On Tue, 2025-10-14 at 17:02 -0500, David Lechner wrote:
> > > Add support for SPI_MULTI_BUS_MODE_STRIPE to the AXI SPI engine driver.
> > > 
> 
> ...
> 
> > > +
> > > +		if (xfer->rx_buf || xfer->offload_flags &
> > > SPI_OFFLOAD_XFER_RX_STREAM ||
> > > +		    xfer->tx_buf || xfer->offload_flags &
> > > SPI_OFFLOAD_XFER_TX_STREAM) {
> > 
> > I'm a bit confused by this condition. It looks like setting priv-
> > >multi_bus_mode
> > (and the other fields) only matters for msg->offload but the above will be
> > true
> > for regular rx/tx messages, right? Or am i missing something?
> 
> You are correct.
> 
> > 
> > If so, I wonder why doing this for all transfers if we only care about
> > multi_bus_mode for offload messages. I guess you want to validate
> > xfer->multi_bus_mode?
> 
> Yes, this is important to validate it since we don't support all possible
> modes.
> The mode still applies to the individual xfer even when not using SPI
> offloading.
> 
> > I would then just take the switch() out of the condition
> > (I mean trying to setup a no data xfer with an invalid bus_mode should also
> > be
> > seen as invalid IMO) and then use the offload conditions (or maybe simply
> > msg-
> > > offload?) for the multi_bus_mode handling. To me, it makes the intent more
> > clear.
> 
> It the validation only matters for xfers that send or receive data. I guess
> it doesn't hurt to check the mode in non-data xfers (e.g. ones with just a
> delay)
> but since we needed the condition anyway for the accumulator, it made sense to
> me to put it inside the conditional.

Sure, but note that I did said that I would tread xfers that do not send/receive
data and have an invalid mode as an error (the flag should not be there anyways)
and that's why I was suggesting taking the validation out of the condition. No
strong feelings though so fine to keep it this way.

- Nuno Sá