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Linux/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         iowrite32(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 ioread32(spi->regs + addr);
 44 }
 45 
 46 static inline void xtfpga_spi_wait_busy(struct xtfpga_spi *xspi)
 47 {
 48         unsigned i;
 49         for (i = 0; xtfpga_spi_read32(xspi, XTFPGA_SPI_BUSY) &&
 50              i < BUSY_WAIT_US; ++i)
 51                 udelay(1);
 52         WARN_ON_ONCE(i == BUSY_WAIT_US);
 53 }
 54 
 55 static u32 xtfpga_spi_txrx_word(struct spi_device *spi, unsigned nsecs,
 56                                 u32 v, u8 bits)
 57 {
 58         struct xtfpga_spi *xspi = spi_master_get_devdata(spi->master);
 59 
 60         xspi->data = (xspi->data << bits) | (v & GENMASK(bits - 1, 0));
 61         xspi->data_sz += bits;
 62         if (xspi->data_sz >= 16) {
 63                 xtfpga_spi_write32(xspi, XTFPGA_SPI_DATA,
 64                                    xspi->data >> (xspi->data_sz - 16));
 65                 xspi->data_sz -= 16;
 66                 xtfpga_spi_write32(xspi, XTFPGA_SPI_START, 1);
 67                 xtfpga_spi_wait_busy(xspi);
 68                 xtfpga_spi_write32(xspi, XTFPGA_SPI_START, 0);
 69         }
 70 
 71         return 0;
 72 }
 73 
 74 static void xtfpga_spi_chipselect(struct spi_device *spi, int is_on)
 75 {
 76         struct xtfpga_spi *xspi = spi_master_get_devdata(spi->master);
 77 
 78         WARN_ON(xspi->data_sz != 0);
 79         xspi->data_sz = 0;
 80 }
 81 
 82 static int xtfpga_spi_probe(struct platform_device *pdev)
 83 {
 84         struct xtfpga_spi *xspi;
 85         struct resource *mem;
 86         int ret;
 87         struct spi_master *master;
 88 
 89         master = spi_alloc_master(&pdev->dev, sizeof(struct xtfpga_spi));
 90         if (!master)
 91                 return -ENOMEM;
 92 
 93         master->flags = SPI_MASTER_NO_RX;
 94         master->bits_per_word_mask = SPI_BPW_RANGE_MASK(1, 16);
 95         master->bus_num = pdev->dev.id;
 96         master->dev.of_node = pdev->dev.of_node;
 97 
 98         xspi = spi_master_get_devdata(master);
 99         xspi->bitbang.master = master;
100         xspi->bitbang.chipselect = xtfpga_spi_chipselect;
101         xspi->bitbang.txrx_word[SPI_MODE_0] = xtfpga_spi_txrx_word;
102 
103         mem = platform_get_resource(pdev, IORESOURCE_MEM, 0);
104         if (!mem) {
105                 dev_err(&pdev->dev, "No memory resource\n");
106                 ret = -ENODEV;
107                 goto err;
108         }
109         xspi->regs = devm_ioremap_resource(&pdev->dev, mem);
110         if (IS_ERR(xspi->regs)) {
111                 ret = PTR_ERR(xspi->regs);
112                 goto err;
113         }
114 
115         xtfpga_spi_write32(xspi, XTFPGA_SPI_START, 0);
116         usleep_range(1000, 2000);
117         if (xtfpga_spi_read32(xspi, XTFPGA_SPI_BUSY)) {
118                 dev_err(&pdev->dev, "Device stuck in busy state\n");
119                 ret = -EBUSY;
120                 goto err;
121         }
122 
123         ret = spi_bitbang_start(&xspi->bitbang);
124         if (ret < 0) {
125                 dev_err(&pdev->dev, "spi_bitbang_start failed\n");
126                 goto err;
127         }
128 
129         platform_set_drvdata(pdev, master);
130         return 0;
131 err:
132         spi_master_put(master);
133         return ret;
134 }
135 
136 static int xtfpga_spi_remove(struct platform_device *pdev)
137 {
138         struct spi_master *master = platform_get_drvdata(pdev);
139         struct xtfpga_spi *xspi = spi_master_get_devdata(master);
140 
141         spi_bitbang_stop(&xspi->bitbang);
142         spi_master_put(master);
143 
144         return 0;
145 }
146 
147 MODULE_ALIAS("platform:" XTFPGA_SPI_NAME);
148 
149 #ifdef CONFIG_OF
150 static const struct of_device_id xtfpga_spi_of_match[] = {
151         { .compatible = "cdns,xtfpga-spi", },
152         {}
153 };
154 MODULE_DEVICE_TABLE(of, xtfpga_spi_of_match);
155 #endif
156 
157 static struct platform_driver xtfpga_spi_driver = {
158         .probe = xtfpga_spi_probe,
159         .remove = xtfpga_spi_remove,
160         .driver = {
161                 .name = XTFPGA_SPI_NAME,
162                 .owner = THIS_MODULE,
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");
171 

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