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Commit 7a5f0b3a authored by Jonathan Cameron's avatar Jonathan Cameron
Browse files

Merge tag 'spi-cs-word' into togreg 

spi: Provide SPI_CS_WORD

This provides a SPI operation mode which changes chip select after every
word, used by some devices such as ADCs and DACs.
parents c8d5b996 cbaa62e0

drivers/spi/spi.c

+30 −1
Original line number Diff line number Diff line
@@ -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

include/linux/spi/spi.h

+1 −1
Original line number Diff line number Diff line
@@ -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

	 *  - ...

	 */