linux/drivers/spi/spi-xtensa-xtfpga.c
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   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
  27struct xtfpga_spi {
  28        struct spi_bitbang bitbang;
  29        void __iomem *regs;
  30        u32 data;
  31        unsigned data_sz;
  32};
  33
  34static inline void xtfpga_spi_write32(const struct xtfpga_spi *spi,
  35                                      unsigned addr, u32 val)
  36{
  37        iowrite32(val, spi->regs + addr);
  38}
  39
  40static inline unsigned int xtfpga_spi_read32(const struct xtfpga_spi *spi,
  41                                             unsigned addr)
  42{
  43        return ioread32(spi->regs + addr);
  44}
  45
  46static 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
  56static 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
  75static 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
  83static 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;
 132err:
 133        spi_master_put(master);
 134        return ret;
 135}
 136
 137static 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
 148MODULE_ALIAS("platform:" XTFPGA_SPI_NAME);
 149
 150#ifdef CONFIG_OF
 151static const struct of_device_id xtfpga_spi_of_match[] = {
 152        { .compatible = "cdns,xtfpga-spi", },
 153        {}
 154};
 155MODULE_DEVICE_TABLE(of, xtfpga_spi_of_match);
 156#endif
 157
 158static 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};
 166module_platform_driver(xtfpga_spi_driver);
 167
 168MODULE_AUTHOR("Max Filippov <jcmvbkbc@gmail.com>");
 169MODULE_DESCRIPTION("xtensa xtfpga SPI driver");
 170MODULE_LICENSE("GPL");
 171
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