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	__raw_writel(val, spi->regs + addr);
38}
39
40static inline unsigned int xtfpga_spi_read32(const struct xtfpga_spi *spi,
41					     unsigned addr)
42{
43	return __raw_readl(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