lpc32xx_ssp.c
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/*
* LPC32xx SSP interface (SPI mode)
*
* (C) Copyright 2014 DENX Software Engineering GmbH
* Written-by: Albert ARIBAUD <albert.aribaud@3adev.fr>
*
* SPDX-License-Identifier: GPL-2.0+
*/
#include <common.h>
#include <linux/compat.h>
#include <asm/io.h>
#include <malloc.h>
#include <spi.h>
#include <asm/arch/clk.h>
/* SSP chip registers */
struct ssp_regs {
u32 cr0;
u32 cr1;
u32 data;
u32 sr;
u32 cpsr;
u32 imsc;
u32 ris;
u32 mis;
u32 icr;
u32 dmacr;
};
/* CR1 register defines */
#define SSP_CR1_SSP_ENABLE 0x0002
/* SR register defines */
#define SSP_SR_TNF 0x0002
/* SSP status RX FIFO not empty bit */
#define SSP_SR_RNE 0x0004
/* lpc32xx spi slave */
struct lpc32xx_spi_slave {
struct spi_slave slave;
struct ssp_regs *regs;
};
static inline struct lpc32xx_spi_slave *to_lpc32xx_spi_slave(
struct spi_slave *slave)
{
return container_of(slave, struct lpc32xx_spi_slave, slave);
}
/* spi_init is called during boot when CONFIG_CMD_SPI is defined */
void spi_init(void)
{
/*
* nothing to do: clocking was enabled in lpc32xx_ssp_enable()
* and configuration will be done in spi_setup_slave()
*/
}
/* the following is called in sequence by do_spi_xfer() */
struct spi_slave *spi_setup_slave(uint bus, uint cs, uint max_hz, uint mode)
{
struct lpc32xx_spi_slave *lslave;
/* we only set up SSP0 for now, so ignore bus */
if (mode & SPI_3WIRE) {
error("3-wire mode not supported");
return NULL;
}
if (mode & SPI_SLAVE) {
error("slave mode not supported\n");
return NULL;
}
if (mode & SPI_PREAMBLE) {
error("preamble byte skipping not supported\n");
return NULL;
}
lslave = spi_alloc_slave(struct lpc32xx_spi_slave, bus, cs);
if (!lslave) {
printf("SPI_error: Fail to allocate lpc32xx_spi_slave\n");
return NULL;
}
lslave->regs = (struct ssp_regs *)SSP0_BASE;
/*
* 8 bit frame, SPI fmt, 500kbps -> clock divider is 26.
* Set SCR to 0 and CPSDVSR to 26.
*/
writel(0x7, &lslave->regs->cr0); /* 8-bit chunks, SPI, 1 clk/bit */
writel(26, &lslave->regs->cpsr); /* SSP clock = HCLK/26 = 500kbps */
writel(0, &lslave->regs->imsc); /* do not raise any interrupts */
writel(0, &lslave->regs->icr); /* clear any pending interrupt */
writel(0, &lslave->regs->dmacr); /* do not do DMAs */
writel(SSP_CR1_SSP_ENABLE, &lslave->regs->cr1); /* enable SSP0 */
return &lslave->slave;
}
void spi_free_slave(struct spi_slave *slave)
{
struct lpc32xx_spi_slave *lslave = to_lpc32xx_spi_slave(slave);
debug("(lpc32xx) spi_free_slave: 0x%08x\n", (u32)lslave);
free(lslave);
}
int spi_claim_bus(struct spi_slave *slave)
{
/* only one bus and slave so far, always available */
return 0;
}
int spi_xfer(struct spi_slave *slave, unsigned int bitlen,
const void *dout, void *din, unsigned long flags)
{
struct lpc32xx_spi_slave *lslave = to_lpc32xx_spi_slave(slave);
int bytelen = bitlen >> 3;
int idx_out = 0;
int idx_in = 0;
int start_time;
start_time = get_timer(0);
while ((idx_out < bytelen) || (idx_in < bytelen)) {
int status = readl(&lslave->regs->sr);
if ((idx_out < bytelen) && (status & SSP_SR_TNF))
writel(((u8 *)dout)[idx_out++], &lslave->regs->data);
if ((idx_in < bytelen) && (status & status & SSP_SR_RNE))
((u8 *)din)[idx_in++] = readl(&lslave->regs->data);
if (get_timer(start_time) >= CONFIG_LPC32XX_SSP_TIMEOUT)
return -1;
}
return 0;
}
void spi_release_bus(struct spi_slave *slave)
{
/* do nothing */
}