From 0baf9eb25572eea0cf48249c1d152d8373956a7c Mon Sep 17 00:00:00 2001 From: David Lechner Date: Wed, 12 Sep 2018 19:39:17 -0500 Subject: [PATCH 1/2] spi: add new SPI_CS_WORD flag This adds a new SPI mode flag, SPI_CS_WORD, that is used to indicate that a SPI device requires the chip select to be toggled after each word that is transferred. Signed-off-by: David Lechner Signed-off-by: Mark Brown --- include/linux/spi/spi.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/spi/spi.h b/include/linux/spi/spi.h index a64235e05321..7cc1466111f5 100644 --- a/include/linux/spi/spi.h +++ b/include/linux/spi/spi.h @@ -163,6 +163,7 @@ struct spi_device { #define SPI_TX_QUAD 0x200 /* transmit with 4 wires */ #define SPI_RX_DUAL 0x400 /* receive with 2 wires */ #define SPI_RX_QUAD 0x800 /* receive with 4 wires */ +#define SPI_CS_WORD 0x1000 /* toggle cs after each word */ int irq; void *controller_state; void *controller_data; @@ -177,7 +178,6 @@ struct spi_device { * the controller talks to each chip, like: * - memory packing (12 bit samples into low bits, others zeroed) * - priority - * - drop chipselect after each word * - chipselect delays * - ... */ From cbaa62e0094a840fecc853910e0c0454529cec03 Mon Sep 17 00:00:00 2001 From: David Lechner Date: Wed, 12 Sep 2018 19:39:18 -0500 Subject: [PATCH 2/2] spi: add software implementation for SPI_CS_WORD 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 --- 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 ec395a6baf9c..be73d236919f 100644 --- a/drivers/spi/spi.c +++ b/drivers/spi/spi.c @@ -2774,8 +2774,10 @@ 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) { @@ -2829,6 +2831,33 @@ 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