Hi, On Mon, 6 Mar 2023 at 18:26, Amit Kumar Mahapatra <amit.kumar-mahapatra@xxxxxxx> wrote: > > For supporting multiple CS the SPI device need to be aware of all the CS > values. So, the "chip_select" member in the spi_device structure is now an > array that holds all the CS values. > > spi_device structure now has a "cs_index_mask" member. This acts as an > index to the chip_select array. If nth bit of spi->cs_index_mask is set > then the driver would assert spi->chip_select[n]. > > In parallel mode all the chip selects are asserted/de-asserted > simultaneously and each byte of data is stored in both devices, the even > bits in one, the odd bits in the other. The split is automatically handled > by the GQSPI controller. The GQSPI controller supports a maximum of two > flashes connected in parallel mode. A "multi-cs-cap" flag is added in the > spi controntroller data, through ctlr->multi-cs-cap the spi core will make > sure that the controller is capable of handling multiple chip selects at > once. > > For supporting multiple CS via GPIO the cs_gpiod member of the spi_device > structure is now an array that holds the gpio descriptor for each > chipselect. > > Multi CS support using GPIO is not tested due to unavailability of > necessary hardware setup. > > Signed-off-by: Amit Kumar Mahapatra <amit.kumar-mahapatra@xxxxxxx> > --- > drivers/spi/spi.c | 213 +++++++++++++++++++++++++++------------- > include/linux/spi/spi.h | 34 +++++-- > 2 files changed, 173 insertions(+), 74 deletions(-) > > diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c > index 5866bf5813a4..8ec7f58fa111 100644 > --- a/drivers/spi/spi.c > +++ b/drivers/spi/spi.c > @@ -613,7 +613,8 @@ static int spi_dev_check(struct device *dev, void *data) > struct spi_device *new_spi = data; > > if (spi->controller == new_spi->controller && > - spi_get_chipselect(spi, 0) == spi_get_chipselect(new_spi, 0)) > + spi_get_chipselect(spi, 0) == spi_get_chipselect(new_spi, 0) && > + spi_get_chipselect(spi, 1) == spi_get_chipselect(new_spi, 1)) > return -EBUSY; This will only reject new devices if both chip selects are identical, but not if they only share one, e.g. CS 1 + 2 vs 1 + 3, or 1 + 2 vs only 2, or if the order is different (1 + 2 vs 2 + 1 - haven't read the code too close to know if this is allowed/possible). Regards, Jonas
