[PATCH v4 3/8] spi: stm32: Add 'SPI_SIMPLEX_RX', 'SPI_3WIRE_RX' support for stm32f4

[dillon min]

On Fri, May 22, 2020 at 10:57 PM dillon min <dillon.minfei at gmail.com> wrote:
>
> hi Mark,
>
> Thanks for reviewing.
>
> On Fri, May 22, 2020 at 7:36 PM Mark Brown <broonie at kernel.org> wrote:
> >
> > On Mon, May 18, 2020 at 07:09:20PM +0800, dillon.minfei at gmail.com wrote:
> >
> > > 2, use stm32 spi's "In full-duplex (BIDIMODE=0 and RXONLY=0)", as tx_buf is
> > > null, we must add dummy data sent out before read data.
> > > so, add stm32f4_spi_tx_dummy() to handle this situation.
> >
> > There are flags SPI_CONTROLLER_MUST_TX and SPI_CONTROLLER_MUST_RX flags
> > that the driver can set if it needs to, no need to open code this in the
> > driver.
>
> Yes, after check SPI_CONTROLLER_MUST_TX in drivers/spi/spi.c , it's
> indeed to meet
> this situation,  i will try it and sumbmit a new patch.
>
> thanks.
>
> best regards
>
> Dillon

Hi Mark,

There might be a conflict with 'SPI_CONTROLLER_MUST_TX' and 'SPI_3WIRE' mode,
i need to know the SPI_3WIRE direction,  currently i get this
information from 'struct spi_device'
and 'struct spi_transfer'
if ((spi_device->mode & SPI_3WIRE) && (spi_transfer->tx_buf == NULL)
&& (spi_transfer->rx_buf != NULL))
    this is a SPI_3WIRE_RX transfer
if ((spi_device->mode & SPI_3WIRE) && (spi_transfer->tx_buf != NULL)
&& (spi_transfer->rx_buf == NULL))
    this is a SPI_3WIRE_TX transfer

but, after spi-core create a dummy tx_buf or rx_buf, then i can't get
the correct spi_3wire direction.
actually, this dummy tx_buf is useless for SPI_3WIRE. it's has meaning
for SPI_SIMPLE_RX mode,
simulate SPI_FULL_DUMPLEX

how do you think?

thanks

best regards

Dillon