drivers/spi/soft_spi.c

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