drivers/spi/lpc32xx_ssp.c

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