drivers/spi/soft_spi.c

   1 /*
   2  * Copyright (c) 2014 Google, Inc
   3  *
   4  * (C) Copyright 2002
   5  * Gerald Van Baren, Custom IDEAS, vanbaren@cideas.com.
   6  *
   7  * Influenced by code from:
   8  * Wolfgang Denk, DENX Software Engineering, wd@denx.de.
   9  *
  10  * SPDX-License-Identifier:     GPL-2.0+
  11  */
  12
  13 #include <common.h>
  14 #include <dm.h>
  15 #include <errno.h>
  16 #include <fdtdec.h>
  17 #include <malloc.h>
  18 #include <spi.h>
  19 #include <asm/gpio.h>
  20
  21 DECLARE_GLOBAL_DATA_PTR;
  22
  23 struct soft_spi_platdata {
  24         struct gpio_desc cs;
  25         struct gpio_desc sclk;
  26         struct gpio_desc mosi;
  27         struct gpio_desc miso;
  28         int spi_delay_us;
  29         int flags;
  30 };
  31
  32 #define SPI_MASTER_NO_RX        BIT(0)
  33 #define SPI_MASTER_NO_TX        BIT(1)
  34
  35 struct soft_spi_priv {
  36         unsigned int mode;
  37 };
  38
  39 static int soft_spi_scl(struct udevice *dev, int bit)
  40 {
  41         struct udevice *bus = dev_get_parent(dev);
  42         struct soft_spi_platdata *plat = dev_get_platdata(bus);
  43
  44         dm_gpio_set_value(&plat->sclk, bit);
  45
  46         return 0;
  47 }
  48
  49 static int soft_spi_sda(struct udevice *dev, int bit)
  50 {
  51         struct udevice *bus = dev_get_parent(dev);
  52         struct soft_spi_platdata *plat = dev_get_platdata(bus);
  53
  54         dm_gpio_set_value(&plat->mosi, bit);
  55
  56         return 0;
  57 }
  58
  59 static int soft_spi_cs_activate(struct udevice *dev)
  60 {
  61         struct udevice *bus = dev_get_parent(dev);
  62         struct soft_spi_platdata *plat = dev_get_platdata(bus);
  63
  64         dm_gpio_set_value(&plat->cs, 0);
  65         dm_gpio_set_value(&plat->sclk, 0);
  66         dm_gpio_set_value(&plat->cs, 1);
  67
  68         return 0;
  69 }
  70
  71 static int soft_spi_cs_deactivate(struct udevice *dev)
  72 {
  73         struct udevice *bus = dev_get_parent(dev);
  74         struct soft_spi_platdata *plat = dev_get_platdata(bus);
  75
  76         dm_gpio_set_value(&plat->cs, 0);
  77
  78         return 0;
  79 }
  80
  81 static int soft_spi_claim_bus(struct udevice *dev)
  82 {
  83         /*
  84          * Make sure the SPI clock is in idle state as defined for
  85          * this slave.
  86          */
  87         return soft_spi_scl(dev, 0);
  88 }
  89
  90 static int soft_spi_release_bus(struct udevice *dev)
  91 {
  92         /* Nothing to do */
  93         return 0;
  94 }
  95
  96 /*-----------------------------------------------------------------------
  97  * SPI transfer
  98  *
  99  * This writes "bitlen" bits out the SPI MOSI port and simultaneously clocks
 100  * "bitlen" bits in the SPI MISO port.  That's just the way SPI works.
 101  *
 102  * The source of the outgoing bits is the "dout" parameter and the
 103  * destination of the input bits is the "din" parameter.  Note that "dout"
 104  * and "din" can point to the same memory location, in which case the
 105  * input data overwrites the output data (since both are buffered by
 106  * temporary variables, this is OK).
 107  */
 108 static int soft_spi_xfer(struct udevice *dev, unsigned int bitlen,
 109                          const void *dout, void *din, unsigned long flags)
 110 {
 111         struct udevice *bus = dev_get_parent(dev);
 112         struct soft_spi_priv *priv = dev_get_priv(bus);
 113         struct soft_spi_platdata *plat = dev_get_platdata(bus);
 114         uchar           tmpdin  = 0;
 115         uchar           tmpdout = 0;
 116         const u8        *txd = dout;
 117         u8              *rxd = din;
 118         int             cpha = priv->mode & SPI_CPHA;
 119         unsigned int    j;
 120
 121         debug("spi_xfer: slave %s:%s dout %08X din %08X bitlen %u\n",
 122               dev->parent->name, dev->name, *(uint *)txd, *(uint *)rxd,
 123               bitlen);
 124
 125         if (flags & SPI_XFER_BEGIN)
 126                 soft_spi_cs_activate(dev);
 127
 128         for (j = 0; j < bitlen; j++) {
 129                 /*
 130                  * Check if it is time to work on a new byte.
 131                  */
 132                 if ((j % 8) == 0) {
 133                         if (txd)
 134                                 tmpdout = *txd++;
 135                         else
 136                                 tmpdout = 0;
 137                         if (j != 0) {
 138                                 if (rxd)
 139                                         *rxd++ = tmpdin;
 140                         }
 141                         tmpdin  = 0;
 142                 }
 143
 144                 if (!cpha)
 145                         soft_spi_scl(dev, 0);
 146                 if ((plat->flags & SPI_MASTER_NO_TX) == 0)
 147                         soft_spi_sda(dev, !!(tmpdout & 0x80));
 148                 udelay(plat->spi_delay_us);
 149                 if (cpha)
 150                         soft_spi_scl(dev, 0);
 151                 else
 152                         soft_spi_scl(dev, 1);
 153                 tmpdin  <<= 1;
 154                 if ((plat->flags & SPI_MASTER_NO_RX) == 0)
 155                         tmpdin  |= dm_gpio_get_value(&plat->miso);
 156                 tmpdout <<= 1;
 157                 udelay(plat->spi_delay_us);
 158                 if (cpha)
 159                         soft_spi_scl(dev, 1);
 160         }
 161         /*
 162          * If the number of bits isn't a multiple of 8, shift the last
 163          * bits over to left-justify them.  Then store the last byte
 164          * read in.
 165          */
 166         if (rxd) {
 167                 if ((bitlen % 8) != 0)
 168                         tmpdin <<= 8 - (bitlen % 8);
 169                 *rxd++ = tmpdin;
 170         }
 171
 172         if (flags & SPI_XFER_END)
 173                 soft_spi_cs_deactivate(dev);
 174
 175         return 0;
 176 }
 177
 178 static int soft_spi_set_speed(struct udevice *dev, unsigned int speed)
 179 {
 180         /* Accept any speed */
 181         return 0;
 182 }
 183
 184 static int soft_spi_set_mode(struct udevice *dev, unsigned int mode)
 185 {
 186         struct soft_spi_priv *priv = dev_get_priv(dev);
 187
 188         priv->mode = mode;
 189
 190         return 0;
 191 }
 192
 193 static const struct dm_spi_ops soft_spi_ops = {
 194         .claim_bus      = soft_spi_claim_bus,
 195         .release_bus    = soft_spi_release_bus,
 196         .xfer           = soft_spi_xfer,
 197         .set_speed      = soft_spi_set_speed,
 198         .set_mode       = soft_spi_set_mode,
 199 };
 200
 201 static int soft_spi_ofdata_to_platdata(struct udevice *dev)
 202 {
 203         struct soft_spi_platdata *plat = dev->platdata;
 204         const void *blob = gd->fdt_blob;
 205         int node = dev_of_offset(dev);
 206
 207         plat->spi_delay_us = fdtdec_get_int(blob, node, "spi-delay-us", 0);
 208
 209         return 0;
 210 }
 211
 212 static int soft_spi_probe(struct udevice *dev)
 213 {
 214         struct spi_slave *slave = dev_get_parent_priv(dev);
 215         struct soft_spi_platdata *plat = dev->platdata;
 216         int cs_flags, clk_flags;
 217         int ret;
 218
 219         cs_flags = (slave->mode & SPI_CS_HIGH) ? 0 : GPIOD_ACTIVE_LOW;
 220         clk_flags = (slave->mode & SPI_CPOL) ? GPIOD_ACTIVE_LOW : 0;
 221
 222         if (gpio_request_by_name(dev, "cs-gpios", 0, &plat->cs,
 223                                  GPIOD_IS_OUT | cs_flags) ||
 224             gpio_request_by_name(dev, "gpio-sck", 0, &plat->sclk,
 225                                  GPIOD_IS_OUT | clk_flags))
 226                 return -EINVAL;
 227
 228         ret = gpio_request_by_name(dev, "gpio-mosi", 0, &plat->mosi,
 229                                    GPIOD_IS_OUT | GPIOD_IS_OUT_ACTIVE);
 230         if (ret)
 231                 plat->flags |= SPI_MASTER_NO_TX;
 232
 233         ret = gpio_request_by_name(dev, "gpio-miso", 0, &plat->miso,
 234                                    GPIOD_IS_IN);
 235         if (ret)
 236                 plat->flags |= SPI_MASTER_NO_RX;
 237
 238         if ((plat->flags & (SPI_MASTER_NO_RX | SPI_MASTER_NO_TX)) ==
 239             (SPI_MASTER_NO_RX | SPI_MASTER_NO_TX))
 240                 return -EINVAL;
 241
 242         return 0;
 243 }
 244
 245 static const struct udevice_id soft_spi_ids[] = {
 246         { .compatible = "spi-gpio" },
 247         { }
 248 };
 249
 250 U_BOOT_DRIVER(soft_spi) = {
 251         .name   = "soft_spi",
 252         .id     = UCLASS_SPI,
 253         .of_match = soft_spi_ids,
 254         .ops    = &soft_spi_ops,
 255         .ofdata_to_platdata = soft_spi_ofdata_to_platdata,
 256         .platdata_auto_alloc_size = sizeof(struct soft_spi_platdata),
 257         .priv_auto_alloc_size = sizeof(struct soft_spi_priv),
 258         .probe  = soft_spi_probe,
 259 };