drivers/spi/lpc32xx_ssp.c

   1 /*
   2  * LPC32xx SSP interface (SPI mode)
   3  *
   4  * (C) Copyright 2014  DENX Software Engineering GmbH
   5  * Written-by: Albert ARIBAUD <albert.aribaud@3adev.fr>
   6  *
   7  * SPDX-License-Identifier:     GPL-2.0+
   8  */
   9
  10 #include <common.h>
  11 #include <linux/compat.h>
  12 #include <asm/io.h>
  13 #include <malloc.h>
  14 #include <spi.h>
  15 #include <asm/arch/clk.h>
  16
  17 /* SSP chip registers */
  18 struct ssp_regs {
  19         u32 cr0;
  20         u32 cr1;
  21         u32 data;
  22         u32 sr;
  23         u32 cpsr;
  24         u32 imsc;
  25         u32 ris;
  26         u32 mis;
  27         u32 icr;
  28         u32 dmacr;
  29 };
  30
  31 /* CR1 register defines  */
  32 #define SSP_CR1_SSP_ENABLE 0x0002
  33
  34 /* SR register defines  */
  35 #define SSP_SR_TNF 0x0002
  36 /* SSP status RX FIFO not empty bit */
  37 #define SSP_SR_RNE 0x0004
  38
  39 /* lpc32xx spi slave */
  40 struct lpc32xx_spi_slave {
  41         struct spi_slave slave;
  42         struct ssp_regs *regs;
  43 };
  44
  45 static inline struct lpc32xx_spi_slave *to_lpc32xx_spi_slave(
  46         struct spi_slave *slave)
  47 {
  48         return container_of(slave, struct lpc32xx_spi_slave, slave);
  49 }
  50
  51 /* spi_init is called during boot when CONFIG_CMD_SPI is defined */
  52 void spi_init(void)
  53 {
  54         /*
  55          *  nothing to do: clocking was enabled in lpc32xx_ssp_enable()
  56          * and configuration will be done in spi_setup_slave()
  57         */
  58 }
  59
  60 /* the following is called in sequence by do_spi_xfer() */
  61
  62 struct spi_slave *spi_setup_slave(uint bus, uint cs, uint max_hz, uint mode)
  63 {
  64         struct lpc32xx_spi_slave *lslave;
  65
  66         /* we only set up SSP0 for now, so ignore bus */
  67
  68         if (mode & SPI_3WIRE) {
  69                 pr_err("3-wire mode not supported");
  70                 return NULL;
  71         }
  72
  73         if (mode & SPI_SLAVE) {
  74                 pr_err("slave mode not supported\n");
  75                 return NULL;
  76         }
  77
  78         if (mode & SPI_PREAMBLE) {
  79                 pr_err("preamble byte skipping not supported\n");
  80                 return NULL;
  81         }
  82
  83         lslave = spi_alloc_slave(struct lpc32xx_spi_slave, bus, cs);
  84         if (!lslave) {
  85                 printf("SPI_error: Fail to allocate lpc32xx_spi_slave\n");
  86                 return NULL;
  87         }
  88
  89         lslave->regs = (struct ssp_regs *)SSP0_BASE;
  90
  91         /*
  92          * 8 bit frame, SPI fmt, 500kbps -> clock divider is 26.
  93          * Set SCR to 0 and CPSDVSR to 26.
  94          */
  95
  96         writel(0x7, &lslave->regs->cr0); /* 8-bit chunks, SPI, 1 clk/bit */
  97         writel(26, &lslave->regs->cpsr); /* SSP clock = HCLK/26 = 500kbps */
  98         writel(0, &lslave->regs->imsc); /* do not raise any interrupts */
  99         writel(0, &lslave->regs->icr); /* clear any pending interrupt */
 100         writel(0, &lslave->regs->dmacr); /* do not do DMAs */
 101         writel(SSP_CR1_SSP_ENABLE, &lslave->regs->cr1); /* enable SSP0 */
 102         return &lslave->slave;
 103 }
 104
 105 void spi_free_slave(struct spi_slave *slave)
 106 {
 107         struct lpc32xx_spi_slave *lslave = to_lpc32xx_spi_slave(slave);
 108
 109         debug("(lpc32xx) spi_free_slave: 0x%08x\n", (u32)lslave);
 110         free(lslave);
 111 }
 112
 113 int spi_claim_bus(struct spi_slave *slave)
 114 {
 115         /* only one bus and slave so far, always available */
 116         return 0;
 117 }
 118
 119 int spi_xfer(struct spi_slave *slave, unsigned int bitlen,
 120         const void *dout, void *din, unsigned long flags)
 121 {
 122         struct lpc32xx_spi_slave *lslave = to_lpc32xx_spi_slave(slave);
 123         int bytelen = bitlen >> 3;
 124         int idx_out = 0;
 125         int idx_in = 0;
 126         int start_time;
 127
 128         start_time = get_timer(0);
 129         while ((idx_out < bytelen) || (idx_in < bytelen)) {
 130                 int status = readl(&lslave->regs->sr);
 131                 if ((idx_out < bytelen) && (status & SSP_SR_TNF))
 132                         writel(((u8 *)dout)[idx_out++], &lslave->regs->data);
 133                 if ((idx_in < bytelen) && (status & status & SSP_SR_RNE))
 134                         ((u8 *)din)[idx_in++] = readl(&lslave->regs->data);
 135                 if (get_timer(start_time) >= CONFIG_LPC32XX_SSP_TIMEOUT)
 136                         return -1;
 137         }
 138         return 0;
 139 }
 140
 141 void spi_release_bus(struct spi_slave *slave)
 142 {
 143         /* do nothing */
 144 }