From 03a6abd5e76a075736888f4ba3f7aeb9c73c6c4e Mon Sep 17 00:00:00 2001 From: David Lechner Date: Wed, 12 Sep 2018 19:39:18 -0500 Subject: [PATCH] spi: add software implementation for SPI_CS_WORD commit cbaa62e0094a840fecc853910e0c0454529cec03 upstream 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 Acked-by: Jonathan Cameron Signed-off-by: Mark Brown Signed-off-by: Zou Cao Reviewed-by: Baoyou Xie --- 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 88a8a8edd44b..4fa35213bd62 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -2785,8 +2785,10 @@ 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) { @@ -2840,6 +2842,33 @@ 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 -- GitLab