ECSPI Slave on i.M8M Mini with DMA

[Adam Ford <aford173@xxxxxxxxx>]

To the NXP team,

I noticed the spi-imx driver has a function called spi_imx_can_dma()
which returns false if the SPI is configured as a slave, so the dma
cannot be used in slave mode.

Section 10.1.2.7 "DMA" of the The 8MM Ref manual, Rev 3, shows there
are a few conditions that can trigger the DMA.  Of them, two are
RXFIFO data request and RXFIFO full.  The block diagram in that
section shows it can retrieve data with DMA

However, in section 10.1.4 "Applications" of the same document, it
shows the optional DMA configurations are only in the SPI master
configuration and not the SPI slave configuration.

The ECSPIx_DMAREG documentation (section 10.1.5.6) states "The ECSPI
sends out DMA requests when the appropriate FIFO conditions are
matched." Unfortunately it doesn't explicitly state whether that's
only for master or available in either master or slave mode.

Can someone tell me if DMA is available when SPI is configured as a slave?

thank you,

adam