drivers/spi/spi-xtensa-xtfpga.c

   1 /*
   2  * Xtensa xtfpga SPI controller driver
   3  *
   4  * Copyright (c) 2014 Cadence Design Systems Inc.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 as
   8  * published by the Free Software Foundation.
   9  */
  10
  11 #include <linux/delay.h>
  12 #include <linux/io.h>
  13 #include <linux/module.h>
  14 #include <linux/of.h>
  15 #include <linux/platform_device.h>
  16 #include <linux/spi/spi.h>
  17 #include <linux/spi/spi_bitbang.h>
  18
  19 #define XTFPGA_SPI_NAME "xtfpga_spi"
  20
  21 #define XTFPGA_SPI_START        0x0
  22 #define XTFPGA_SPI_BUSY         0x4
  23 #define XTFPGA_SPI_DATA         0x8
  24
  25 #define BUSY_WAIT_US            100
  26
  27 struct xtfpga_spi {
  28         struct spi_bitbang bitbang;
  29         void __iomem *regs;
  30         u32 data;
  31         unsigned data_sz;
  32 };
  33
  34 static inline void xtfpga_spi_write32(const struct xtfpga_spi *spi,
  35                                       unsigned addr, u32 val)
  36 {
  37         __raw_writel(val, spi->regs + addr);
  38 }
  39
  40 static inline unsigned int xtfpga_spi_read32(const struct xtfpga_spi *spi,
  41                                              unsigned addr)
  42 {
  43         return __raw_readl(spi->regs + addr);
  44 }
  45
  46 static inline void xtfpga_spi_wait_busy(struct xtfpga_spi *xspi)
  47 {
  48         unsigned i;
  49
  50         for (i = 0; xtfpga_spi_read32(xspi, XTFPGA_SPI_BUSY) &&
  51              i < BUSY_WAIT_US; ++i)
  52                 udelay(1);
  53         WARN_ON_ONCE(i == BUSY_WAIT_US);
  54 }
  55
  56 static u32 xtfpga_spi_txrx_word(struct spi_device *spi, unsigned nsecs,
  57                                 u32 v, u8 bits)
  58 {
  59         struct xtfpga_spi *xspi = spi_master_get_devdata(spi->master);
  60
  61         xspi->data = (xspi->data << bits) | (v & GENMASK(bits - 1, 0));
  62         xspi->data_sz += bits;
  63         if (xspi->data_sz >= 16) {
  64                 xtfpga_spi_write32(xspi, XTFPGA_SPI_DATA,
  65                                    xspi->data >> (xspi->data_sz - 16));
  66                 xspi->data_sz -= 16;
  67                 xtfpga_spi_write32(xspi, XTFPGA_SPI_START, 1);
  68                 xtfpga_spi_wait_busy(xspi);
  69                 xtfpga_spi_write32(xspi, XTFPGA_SPI_START, 0);
  70         }
  71
  72         return 0;
  73 }
  74
  75 static void xtfpga_spi_chipselect(struct spi_device *spi, int is_on)
  76 {
  77         struct xtfpga_spi *xspi = spi_master_get_devdata(spi->master);
  78
  79         WARN_ON(xspi->data_sz != 0);
  80         xspi->data_sz = 0;
  81 }
  82
  83 static int xtfpga_spi_probe(struct platform_device *pdev)
  84 {
  85         struct xtfpga_spi *xspi;
  86         struct resource *mem;
  87         int ret;
  88         struct spi_master *master;
  89
  90         master = spi_alloc_master(&pdev->dev, sizeof(struct xtfpga_spi));
  91         if (!master)
  92                 return -ENOMEM;
  93
  94         master->flags = SPI_MASTER_NO_RX;
  95         master->bits_per_word_mask = SPI_BPW_RANGE_MASK(1, 16);
  96         master->bus_num = pdev->dev.id;
  97         master->dev.of_node = pdev->dev.of_node;
  98
  99         xspi = spi_master_get_devdata(master);
 100         xspi->bitbang.master = master;
 101         xspi->bitbang.chipselect = xtfpga_spi_chipselect;
 102         xspi->bitbang.txrx_word[SPI_MODE_0] = xtfpga_spi_txrx_word;
 103
 104         mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 105         if (!mem) {
 106                 dev_err(&pdev->dev, "No memory resource\n");
 107                 ret = -ENODEV;
 108                 goto err;
 109         }
 110         xspi->regs = devm_ioremap_resource(&pdev->dev, mem);
 111         if (IS_ERR(xspi->regs)) {
 112                 ret = PTR_ERR(xspi->regs);
 113                 goto err;
 114         }
 115
 116         xtfpga_spi_write32(xspi, XTFPGA_SPI_START, 0);
 117         usleep_range(1000, 2000);
 118         if (xtfpga_spi_read32(xspi, XTFPGA_SPI_BUSY)) {
 119                 dev_err(&pdev->dev, "Device stuck in busy state\n");
 120                 ret = -EBUSY;
 121                 goto err;
 122         }
 123
 124         ret = spi_bitbang_start(&xspi->bitbang);
 125         if (ret < 0) {
 126                 dev_err(&pdev->dev, "spi_bitbang_start failed\n");
 127                 goto err;
 128         }
 129
 130         platform_set_drvdata(pdev, master);
 131         return 0;
 132 err:
 133         spi_master_put(master);
 134         return ret;
 135 }
 136
 137 static int xtfpga_spi_remove(struct platform_device *pdev)
 138 {
 139         struct spi_master *master = platform_get_drvdata(pdev);
 140         struct xtfpga_spi *xspi = spi_master_get_devdata(master);
 141
 142         spi_bitbang_stop(&xspi->bitbang);
 143         spi_master_put(master);
 144
 145         return 0;
 146 }
 147
 148 MODULE_ALIAS("platform:" XTFPGA_SPI_NAME);
 149
 150 #ifdef CONFIG_OF
 151 static const struct of_device_id xtfpga_spi_of_match[] = {
 152         { .compatible = "cdns,xtfpga-spi", },
 153         {}
 154 };
 155 MODULE_DEVICE_TABLE(of, xtfpga_spi_of_match);
 156 #endif
 157
 158 static struct platform_driver xtfpga_spi_driver = {
 159         .probe = xtfpga_spi_probe,
 160         .remove = xtfpga_spi_remove,
 161         .driver = {
 162                 .name = XTFPGA_SPI_NAME,
 163                 .of_match_table = of_match_ptr(xtfpga_spi_of_match),
 164         },
 165 };
 166 module_platform_driver(xtfpga_spi_driver);
 167
 168 MODULE_AUTHOR("Max Filippov <jcmvbkbc@gmail.com>");
 169 MODULE_DESCRIPTION("xtensa xtfpga SPI driver");
 170 MODULE_LICENSE("GPL");