Re: [PATCH v2 4/6] spi: axi-spi-engine: support SPI_MULTI_BUS_MODE_STRIPE

[David Lechner <dlechner@baylibre.com>]

On 11/11/25 9:12 AM, Marcelo Schmitt wrote:
> Hi David,
> 
> The updates to spi-engine driver look good.
> Only one comment about what happens if we have conflicting bus modes for the
> offload case. Just to check I'm getting how this is working.
> 

...

>> @@ -284,6 +316,24 @@ static int spi_engine_precompile_message(struct spi_message *msg)
>>  			min_bits_per_word = min(min_bits_per_word, xfer->bits_per_word);
>>  			max_bits_per_word = max(max_bits_per_word, xfer->bits_per_word);
>>  		}
>> +
>> +		if (xfer->rx_buf || xfer->offload_flags & SPI_OFFLOAD_XFER_RX_STREAM ||
>> +		    xfer->tx_buf || xfer->offload_flags & SPI_OFFLOAD_XFER_TX_STREAM) {
>> +			switch (xfer->multi_bus_mode) {
>> +			case SPI_MULTI_BUS_MODE_SINGLE:
>> +			case SPI_MULTI_BUS_MODE_STRIPE:
>> +				break;
>> +			default:
>> +				/* Other modes, like mirror not supported */
>> +				return -EINVAL;
>> +			}
>> +
>> +			/* If all xfers have the same multi-bus mode, we can optimize. */
>> +			if (multi_bus_mode == SPI_ENGINE_MULTI_BUS_MODE_UNKNOWN)
>> +				multi_bus_mode = xfer->multi_bus_mode;
>> +			else if (multi_bus_mode != xfer->multi_bus_mode)
>> +				multi_bus_mode = SPI_ENGINE_MULTI_BUS_MODE_CONFLICTING;
> 
> Here we check all xfers have the same multi-bus mode and keep the mode that has
> been set. Otherwise, we set this conflicting mode and the intent is to generate
> SDI and SDO mask commands on demand on spi_engine_precompile_message(). OTOH,

s/spi_engine_precompile_message/spi_engine_compile_message/

Probably just a typo, but just to be clear, the "on demand" bit happens in the
compile function rather than precompile.

> if all xfers have the same multi-bus mode, we can add just one pair of SDI/SDO
> mask commands in spi_engine_trigger_enable() and one pair latter in
> spi_engine_trigger_disable(). I guess this is the optimization mentioned in the
> comment.
> 
Your understanding is correct.