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, unsigned flags)
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");
171