u-boot/drivers/spi/soft_spi_legacy.c

// SPDX-License-Identifier: GPL-2.0+
/*
 * (C) Copyright 2002
 * Gerald Van Baren, Custom IDEAS, vanbaren@cideas.com.
 *
 * Influenced by code from:
 * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
 */

#include <common.h>
#include <spi.h>

#include <malloc.h>

/*-----------------------------------------------------------------------
 * Definitions
 */

#ifdef DEBUG_SPI
#define PRINTD(fmt,args...)	printf (fmt ,##args)
#else
#define PRINTD(fmt,args...)
#endif

struct soft_spi_slave {
	struct spi_slave slave;
	unsigned int mode;
};

static inline struct soft_spi_slave *to_soft_spi(struct spi_slave *slave)
{
	return container_of(slave, struct soft_spi_slave, slave);
}

/*=====================================================================*/
/*                         Public Functions                            */
/*=====================================================================*/

struct spi_slave *spi_setup_slave(unsigned int bus, unsigned int cs,
		unsigned int max_hz, unsigned int mode)
{
	struct soft_spi_slave *ss;

	if (!spi_cs_is_valid(bus, cs))
		return NULL;

	ss = spi_alloc_slave(struct soft_spi_slave, bus, cs);
	if (!ss)
		return NULL;

	ss->mode = mode;

	/* TODO: Use max_hz to limit the SCK rate */

	return &ss->slave;
}

void spi_free_slave(struct spi_slave *slave)
{
	struct soft_spi_slave *ss = to_soft_spi(slave);

	free(ss);
}

int spi_claim_bus(struct spi_slave *slave)
{
#ifdef CONFIG_SYS_IMMR
	volatile immap_t *immr = (immap_t *)CONFIG_SYS_IMMR;
#endif
	struct soft_spi_slave *ss = to_soft_spi(slave);

	/*
	 * Make sure the SPI clock is in idle state as defined for
	 * this slave.
	 */
	if (ss->mode & SPI_CPOL)
		SPI_SCL(1);
	else
		SPI_SCL(0);

	return 0;
}

void spi_release_bus(struct spi_slave *slave)
{
	/* Nothing to do */
}

/*-----------------------------------------------------------------------
 * SPI transfer
 *
 * This writes "bitlen" bits out the SPI MOSI port and simultaneously clocks
 * "bitlen" bits in the SPI MISO port.  That's just the way SPI works.
 *
 * The source of the outgoing bits is the "dout" parameter and the
 * destination of the input bits is the "din" parameter.  Note that "dout"
 * and "din" can point to the same memory location, in which case the
 * input data overwrites the output data (since both are buffered by
 * temporary variables, this is OK).
 */
int  spi_xfer(struct spi_slave *slave, unsigned int bitlen,
		const void *dout, void *din, unsigned long flags)
{
#ifdef CONFIG_SYS_IMMR
	volatile immap_t *immr = (immap_t *)CONFIG_SYS_IMMR;
#endif
	struct soft_spi_slave *ss = to_soft_spi(slave);
	uchar		tmpdin  = 0;
	uchar		tmpdout = 0;
	const u8	*txd = dout;
	u8		*rxd = din;
	int		cpol = ss->mode & SPI_CPOL;
	int		cpha = ss->mode & SPI_CPHA;
	unsigned int	j;

	PRINTD("spi_xfer: slave %u:%u dout %08X din %08X bitlen %u\n",
		slave->bus, slave->cs, *(uint *)txd, *(uint *)rxd, bitlen);

	if (flags & SPI_XFER_BEGIN)
		spi_cs_activate(slave);

	for(j = 0; j < bitlen; j++) {
		/*
		 * Check if it is time to work on a new byte.
		 */
		if ((j % 8) == 0) {
			if (txd)
				tmpdout = *txd++;
			else
				tmpdout = 0;
			if(j != 0) {
				if (rxd)
					*rxd++ = tmpdin;
			}
			tmpdin  = 0;
		}

		if (!cpha)
			SPI_SCL(!cpol);
		SPI_SDA(tmpdout & 0x80);
		SPI_DELAY;
		if (cpha)
			SPI_SCL(!cpol);
		else
			SPI_SCL(cpol);
		tmpdin	<<= 1;
		tmpdin	|= SPI_READ;
		tmpdout	<<= 1;
		SPI_DELAY;
		if (cpha)
			SPI_SCL(cpol);
	}
	/*
	 * If the number of bits isn't a multiple of 8, shift the last
	 * bits over to left-justify them.  Then store the last byte
	 * read in.
	 */
	if (rxd) {
		if ((bitlen % 8) != 0)
			tmpdin <<= 8 - (bitlen % 8);
		*rxd++ = tmpdin;
	}

	if (flags & SPI_XFER_END)
		spi_cs_deactivate(slave);

	return(0);
}