| Message ID | 20180913003920.30600-3-david@lechnology.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | spi: introduce SPI_CS_WORD mode flag | expand |
On Wed, 12 Sep 2018 19:39:18 -0500 David Lechner <david@lechnology.com> wrote: > This adds a default software implementation for the SPI_CS_WORD flag for > controllers that don't have such a feature. > > The SPI_CS_WORD flag indicates that the CS line should be toggled > between each word sent, not just between each transfer. The > implementation works by using existing functions to split transfers into > one-word-sized transfers and sets the cs_change bit for each of the > new transfers. > > Signed-off-by: David Lechner <david@lechnology.com> Looks good to me but I'm not that familiar with this code.. Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com> > --- > drivers/spi/spi.c | 31 +++++++++++++++++++++++++++++++- > 1 file changed, 30 insertions(+), 1 deletion(-) > > diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c > index 9da0bc5a036c..84518ed58872 100644 > --- a/drivers/spi/spi.c > +++ b/drivers/spi/spi.c > @@ -2783,8 +2783,10 @@ int spi_setup(struct spi_device *spi) > return -EINVAL; > /* help drivers fail *cleanly* when they need options > * that aren't supported with their current controller > + * SPI_CS_WORD has a fallback software implementation, > + * so it is ignored here. > */ > - bad_bits = spi->mode & ~spi->controller->mode_bits; > + bad_bits = spi->mode & ~(spi->controller->mode_bits | SPI_CS_WORD); > ugly_bits = bad_bits & > (SPI_TX_DUAL | SPI_TX_QUAD | SPI_RX_DUAL | SPI_RX_QUAD); > if (ugly_bits) { > @@ -2838,6 +2840,33 @@ static int __spi_validate(struct spi_device *spi, struct spi_message *message) > if (list_empty(&message->transfers)) > return -EINVAL; > > + /* If an SPI controller does not support toggling the CS line on each > + * transfer (indicated by the SPI_CS_WORD flag), we can emulate it by > + * splitting transfers into one-word transfers and ensuring that > + * cs_change is set for each transfer. > + */ > + if ((spi->mode & SPI_CS_WORD) && !(ctlr->mode_bits & SPI_CS_WORD)) { > + size_t maxsize; > + int ret; > + > + maxsize = (spi->bits_per_word + 7) / 8; > + > + /* spi_split_transfers_maxsize() requires message->spi */ > + message->spi = spi; > + > + ret = spi_split_transfers_maxsize(ctlr, message, maxsize, > + GFP_KERNEL); > + if (ret) > + return ret; > + > + list_for_each_entry(xfer, &message->transfers, transfer_list) { > + /* don't change cs_change on the last entry in the list */ > + if (list_is_last(&xfer->transfer_list, &message->transfers)) > + break; > + xfer->cs_change = 1; > + } > + } > + > /* Half-duplex links include original MicroWire, and ones with > * only one data pin like SPI_3WIRE (switches direction) or where > * either MOSI or MISO is missing. They can also be caused by
diff --git a/drivers/spi/spi.c b/drivers/spi/spi.c index 9da0bc5a036c..84518ed58872 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -2783,8 +2783,10 @@ int spi_setup(struct spi_device *spi) return -EINVAL; /* help drivers fail *cleanly* when they need options * that aren't supported with their current controller + * SPI_CS_WORD has a fallback software implementation, + * so it is ignored here. */ - bad_bits = spi->mode & ~spi->controller->mode_bits; + bad_bits = spi->mode & ~(spi->controller->mode_bits | SPI_CS_WORD); ugly_bits = bad_bits & (SPI_TX_DUAL | SPI_TX_QUAD | SPI_RX_DUAL | SPI_RX_QUAD); if (ugly_bits) { @@ -2838,6 +2840,33 @@ static int __spi_validate(struct spi_device *spi, struct spi_message *message) if (list_empty(&message->transfers)) return -EINVAL; + /* If an SPI controller does not support toggling the CS line on each + * transfer (indicated by the SPI_CS_WORD flag), we can emulate it by + * splitting transfers into one-word transfers and ensuring that + * cs_change is set for each transfer. + */ + if ((spi->mode & SPI_CS_WORD) && !(ctlr->mode_bits & SPI_CS_WORD)) { + size_t maxsize; + int ret; + + maxsize = (spi->bits_per_word + 7) / 8; + + /* spi_split_transfers_maxsize() requires message->spi */ + message->spi = spi; + + ret = spi_split_transfers_maxsize(ctlr, message, maxsize, + GFP_KERNEL); + if (ret) + return ret; + + list_for_each_entry(xfer, &message->transfers, transfer_list) { + /* don't change cs_change on the last entry in the list */ + if (list_is_last(&xfer->transfer_list, &message->transfers)) + break; + xfer->cs_change = 1; + } + } + /* Half-duplex links include original MicroWire, and ones with * only one data pin like SPI_3WIRE (switches direction) or where * either MOSI or MISO is missing. They can also be caused by
This adds a default software implementation for the SPI_CS_WORD flag for controllers that don't have such a feature. The SPI_CS_WORD flag indicates that the CS line should be toggled between each word sent, not just between each transfer. The implementation works by using existing functions to split transfers into one-word-sized transfers and sets the cs_change bit for each of the new transfers. Signed-off-by: David Lechner <david@lechnology.com> --- drivers/spi/spi.c | 31 +++++++++++++++++++++++++++++++- 1 file changed, 30 insertions(+), 1 deletion(-)