drivers/spi/spi-jcore.c

   1 /*
   2  * J-Core SPI controller driver
   3  *
   4  * Copyright (C) 2012-2016 Smart Energy Instruments, Inc.
   5  *
   6  * Current version by Rich Felker
   7  * Based loosely on initial version by Oleksandr G Zhadan
   8  *
   9  */
  10 #include <linux/init.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/errno.h>
  13 #include <linux/module.h>
  14 #include <linux/platform_device.h>
  15 #include <linux/spi/spi.h>
  16 #include <linux/clk.h>
  17 #include <linux/err.h>
  18 #include <linux/io.h>
  19 #include <linux/of.h>
  20 #include <linux/delay.h>
  21
  22 #define DRV_NAME        "jcore_spi"
  23
  24 #define CTRL_REG        0x0
  25 #define DATA_REG        0x4
  26
  27 #define JCORE_SPI_CTRL_XMIT             0x02
  28 #define JCORE_SPI_STAT_BUSY             0x02
  29 #define JCORE_SPI_CTRL_LOOP             0x08
  30 #define JCORE_SPI_CTRL_CS_BITS          0x15
  31
  32 #define JCORE_SPI_WAIT_RDY_MAX_LOOP     2000000
  33
  34 struct jcore_spi {
  35         struct spi_master *master;
  36         void __iomem *base;
  37         unsigned int cs_reg;
  38         unsigned int speed_reg;
  39         unsigned int speed_hz;
  40         unsigned int clock_freq;
  41 };
  42
  43 static int jcore_spi_wait(void __iomem *ctrl_reg)
  44 {
  45         unsigned timeout = JCORE_SPI_WAIT_RDY_MAX_LOOP;
  46
  47         do {
  48                 if (!(readl(ctrl_reg) & JCORE_SPI_STAT_BUSY))
  49                         return 0;
  50                 cpu_relax();
  51         } while (--timeout);
  52
  53         return -EBUSY;
  54 }
  55
  56 static void jcore_spi_program(struct jcore_spi *hw)
  57 {
  58         void __iomem *ctrl_reg = hw->base + CTRL_REG;
  59
  60         if (jcore_spi_wait(ctrl_reg))
  61                 dev_err(hw->master->dev.parent,
  62                         "timeout waiting to program ctrl reg.\n");
  63
  64         writel(hw->cs_reg | hw->speed_reg, ctrl_reg);
  65 }
  66
  67 static void jcore_spi_chipsel(struct spi_device *spi, bool value)
  68 {
  69         struct jcore_spi *hw = spi_master_get_devdata(spi->master);
  70         u32 csbit = 1U << (2 * spi->chip_select);
  71
  72         dev_dbg(hw->master->dev.parent, "chipselect %d\n", spi->chip_select);
  73
  74         if (value)
  75                 hw->cs_reg |= csbit;
  76         else
  77                 hw->cs_reg &= ~csbit;
  78
  79         jcore_spi_program(hw);
  80 }
  81
  82 static void jcore_spi_baudrate(struct jcore_spi *hw, int speed)
  83 {
  84         if (speed == hw->speed_hz) return;
  85         hw->speed_hz = speed;
  86         if (speed >= hw->clock_freq / 2)
  87                 hw->speed_reg = 0;
  88         else
  89                 hw->speed_reg = ((hw->clock_freq / 2 / speed) - 1) << 27;
  90         jcore_spi_program(hw);
  91         dev_dbg(hw->master->dev.parent, "speed=%d reg=0x%x\n",
  92                 speed, hw->speed_reg);
  93 }
  94
  95 static int jcore_spi_txrx(struct spi_master *master, struct spi_device *spi,
  96                           struct spi_transfer *t)
  97 {
  98         struct jcore_spi *hw = spi_master_get_devdata(master);
  99
 100         void __iomem *ctrl_reg = hw->base + CTRL_REG;
 101         void __iomem *data_reg = hw->base + DATA_REG;
 102         u32 xmit;
 103
 104         /* data buffers */
 105         const unsigned char *tx;
 106         unsigned char *rx;
 107         unsigned int len;
 108         unsigned int count;
 109
 110         jcore_spi_baudrate(hw, t->speed_hz);
 111
 112         xmit = hw->cs_reg | hw->speed_reg | JCORE_SPI_CTRL_XMIT;
 113         tx = t->tx_buf;
 114         rx = t->rx_buf;
 115         len = t->len;
 116
 117         for (count = 0; count < len; count++) {
 118                 if (jcore_spi_wait(ctrl_reg))
 119                         break;
 120
 121                 writel(tx ? *tx++ : 0, data_reg);
 122                 writel(xmit, ctrl_reg);
 123
 124                 if (jcore_spi_wait(ctrl_reg))
 125                         break;
 126
 127                 if (rx)
 128                         *rx++ = readl(data_reg);
 129         }
 130
 131         spi_finalize_current_transfer(master);
 132
 133         if (count < len)
 134                 return -EREMOTEIO;
 135
 136         return 0;
 137 }
 138
 139 static int jcore_spi_probe(struct platform_device *pdev)
 140 {
 141         struct device_node *node = pdev->dev.of_node;
 142         struct jcore_spi *hw;
 143         struct spi_master *master;
 144         struct resource *res;
 145         u32 clock_freq;
 146         struct clk *clk;
 147         int err = -ENODEV;
 148
 149         master = spi_alloc_master(&pdev->dev, sizeof(struct jcore_spi));
 150         if (!master)
 151                 return err;
 152
 153         /* Setup the master state. */
 154         master->num_chipselect = 3;
 155         master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
 156         master->transfer_one = jcore_spi_txrx;
 157         master->set_cs = jcore_spi_chipsel;
 158         master->dev.of_node = node;
 159         master->bus_num = pdev->id;
 160
 161         hw = spi_master_get_devdata(master);
 162         hw->master = master;
 163         platform_set_drvdata(pdev, hw);
 164
 165         /* Find and map our resources */
 166         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 167         if (!res)
 168                 goto exit_busy;
 169         if (!devm_request_mem_region(&pdev->dev, res->start,
 170                                      resource_size(res), pdev->name))
 171                 goto exit_busy;
 172         hw->base = devm_ioremap_nocache(&pdev->dev, res->start,
 173                                         resource_size(res));
 174         if (!hw->base)
 175                 goto exit_busy;
 176
 177         /*
 178          * The SPI clock rate controlled via a configurable clock divider
 179          * which is applied to the reference clock. A 50 MHz reference is
 180          * most suitable for obtaining standard SPI clock rates, but some
 181          * designs may have a different reference clock, and the DT must
 182          * make the driver aware so that it can properly program the
 183          * requested rate. If the clock is omitted, 50 MHz is assumed.
 184          */
 185         clock_freq = 50000000;
 186         clk = devm_clk_get(&pdev->dev, "ref_clk");
 187         if (!IS_ERR(clk)) {
 188                 if (clk_prepare_enable(clk) == 0) {
 189                         clock_freq = clk_get_rate(clk);
 190                         clk_disable_unprepare(clk);
 191                 } else
 192                         dev_warn(&pdev->dev, "could not enable ref_clk\n");
 193         }
 194         hw->clock_freq = clock_freq;
 195
 196         /* Initialize all CS bits to high. */
 197         hw->cs_reg = JCORE_SPI_CTRL_CS_BITS;
 198         jcore_spi_baudrate(hw, 400000);
 199
 200         /* Register our spi controller */
 201         err = devm_spi_register_master(&pdev->dev, master);
 202         if (err)
 203                 goto exit;
 204
 205         return 0;
 206
 207 exit_busy:
 208         err = -EBUSY;
 209 exit:
 210         spi_master_put(master);
 211         return err;
 212 }
 213
 214 static const struct of_device_id jcore_spi_of_match[] = {
 215         { .compatible = "jcore,spi2" },
 216         {},
 217 };
 218 MODULE_DEVICE_TABLE(of, jcore_spi_of_match);
 219
 220 static struct platform_driver jcore_spi_driver = {
 221         .probe = jcore_spi_probe,
 222         .driver = {
 223                 .name = DRV_NAME,
 224                 .of_match_table = jcore_spi_of_match,
 225         },
 226 };
 227
 228 module_platform_driver(jcore_spi_driver);
 229
 230 MODULE_DESCRIPTION("J-Core SPI driver");
 231 MODULE_AUTHOR("Rich Felker <dalias@libc.org>");
 232 MODULE_LICENSE("GPL");
 233 MODULE_ALIAS("platform:" DRV_NAME);