1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * OpenCores tiny SPI host driver
4 *
5 * https://opencores.org/project,tiny_spi
6 *
7 * Copyright (C) 2011 Thomas Chou <thomas@wytron.com.tw>
8 *
9 * Based on spi_s3c24xx.c, which is:
10 * Copyright (c) 2006 Ben Dooks
11 * Copyright (c) 2006 Simtec Electronics
12 *	Ben Dooks <ben@simtec.co.uk>
13 */
14
15#include <linux/interrupt.h>
16#include <linux/errno.h>
17#include <linux/module.h>
18#include <linux/platform_device.h>
19#include <linux/spi/spi.h>
20#include <linux/spi/spi_bitbang.h>
21#include <linux/spi/spi_oc_tiny.h>
22#include <linux/io.h>
23#include <linux/of.h>
24
25#define DRV_NAME "spi_oc_tiny"
26
27#define TINY_SPI_RXDATA 0
28#define TINY_SPI_TXDATA 4
29#define TINY_SPI_STATUS 8
30#define TINY_SPI_CONTROL 12
31#define TINY_SPI_BAUD 16
32
33#define TINY_SPI_STATUS_TXE 0x1
34#define TINY_SPI_STATUS_TXR 0x2
35
36struct tiny_spi {
37	/* bitbang has to be first */
38	struct spi_bitbang bitbang;
39	struct completion done;
40
41	void __iomem *base;
42	int irq;
43	unsigned int freq;
44	unsigned int baudwidth;
45	unsigned int baud;
46	unsigned int speed_hz;
47	unsigned int mode;
48	unsigned int len;
49	unsigned int txc, rxc;
50	const u8 *txp;
51	u8 *rxp;
52};
53
54static inline struct tiny_spi *tiny_spi_to_hw(struct spi_device *sdev)
55{
56	return spi_controller_get_devdata(sdev->controller);
57}
58
59static unsigned int tiny_spi_baud(struct spi_device *spi, unsigned int hz)
60{
61	struct tiny_spi *hw = tiny_spi_to_hw(spi);
62
63	return min(DIV_ROUND_UP(hw->freq, hz * 2), (1U << hw->baudwidth)) - 1;
64}
65
66static int tiny_spi_setup_transfer(struct spi_device *spi,
67				   struct spi_transfer *t)
68{
69	struct tiny_spi *hw = tiny_spi_to_hw(spi);
70	unsigned int baud = hw->baud;
71
72	if (t) {
73		if (t->speed_hz && t->speed_hz != hw->speed_hz)
74			baud = tiny_spi_baud(spi, t->speed_hz);
75	}
76	writel(baud, hw->base + TINY_SPI_BAUD);
77	writel(hw->mode, hw->base + TINY_SPI_CONTROL);
78	return 0;
79}
80
81static int tiny_spi_setup(struct spi_device *spi)
82{
83	struct tiny_spi *hw = tiny_spi_to_hw(spi);
84
85	if (spi->max_speed_hz != hw->speed_hz) {
86		hw->speed_hz = spi->max_speed_hz;
87		hw->baud = tiny_spi_baud(spi, hw->speed_hz);
88	}
89	hw->mode = spi->mode & SPI_MODE_X_MASK;
90	return 0;
91}
92
93static inline void tiny_spi_wait_txr(struct tiny_spi *hw)
94{
95	while (!(readb(hw->base + TINY_SPI_STATUS) &
96		 TINY_SPI_STATUS_TXR))
97		cpu_relax();
98}
99
100static inline void tiny_spi_wait_txe(struct tiny_spi *hw)
101{
102	while (!(readb(hw->base + TINY_SPI_STATUS) &
103		 TINY_SPI_STATUS_TXE))
104		cpu_relax();
105}
106
107static int tiny_spi_txrx_bufs(struct spi_device *spi, struct spi_transfer *t)
108{
109	struct tiny_spi *hw = tiny_spi_to_hw(spi);
110	const u8 *txp = t->tx_buf;
111	u8 *rxp = t->rx_buf;
112	unsigned int i;
113
114	if (hw->irq >= 0) {
115		/* use interrupt driven data transfer */
116		hw->len = t->len;
117		hw->txp = t->tx_buf;
118		hw->rxp = t->rx_buf;
119		hw->txc = 0;
120		hw->rxc = 0;
121
122		/* send the first byte */
123		if (t->len > 1) {
124			writeb(hw->txp ? *hw->txp++ : 0,
125			       hw->base + TINY_SPI_TXDATA);
126			hw->txc++;
127			writeb(hw->txp ? *hw->txp++ : 0,
128			       hw->base + TINY_SPI_TXDATA);
129			hw->txc++;
130			writeb(TINY_SPI_STATUS_TXR, hw->base + TINY_SPI_STATUS);
131		} else {
132			writeb(hw->txp ? *hw->txp++ : 0,
133			       hw->base + TINY_SPI_TXDATA);
134			hw->txc++;
135			writeb(TINY_SPI_STATUS_TXE, hw->base + TINY_SPI_STATUS);
136		}
137
138		wait_for_completion(&hw->done);
139	} else {
140		/* we need to tighten the transfer loop */
141		writeb(txp ? *txp++ : 0, hw->base + TINY_SPI_TXDATA);
142		for (i = 1; i < t->len; i++) {
143			writeb(txp ? *txp++ : 0, hw->base + TINY_SPI_TXDATA);
144
145			if (rxp || (i != t->len - 1))
146				tiny_spi_wait_txr(hw);
147			if (rxp)
148				*rxp++ = readb(hw->base + TINY_SPI_TXDATA);
149		}
150		tiny_spi_wait_txe(hw);
151		if (rxp)
152			*rxp++ = readb(hw->base + TINY_SPI_RXDATA);
153	}
154
155	return t->len;
156}
157
158static irqreturn_t tiny_spi_irq(int irq, void *dev)
159{
160	struct tiny_spi *hw = dev;
161
162	writeb(0, hw->base + TINY_SPI_STATUS);
163	if (hw->rxc + 1 == hw->len) {
164		if (hw->rxp)
165			*hw->rxp++ = readb(hw->base + TINY_SPI_RXDATA);
166		hw->rxc++;
167		complete(&hw->done);
168	} else {
169		if (hw->rxp)
170			*hw->rxp++ = readb(hw->base + TINY_SPI_TXDATA);
171		hw->rxc++;
172		if (hw->txc < hw->len) {
173			writeb(hw->txp ? *hw->txp++ : 0,
174			       hw->base + TINY_SPI_TXDATA);
175			hw->txc++;
176			writeb(TINY_SPI_STATUS_TXR,
177			       hw->base + TINY_SPI_STATUS);
178		} else {
179			writeb(TINY_SPI_STATUS_TXE,
180			       hw->base + TINY_SPI_STATUS);
181		}
182	}
183	return IRQ_HANDLED;
184}
185
186#ifdef CONFIG_OF
187#include <linux/of_gpio.h>
188
189static int tiny_spi_of_probe(struct platform_device *pdev)
190{
191	struct tiny_spi *hw = platform_get_drvdata(pdev);
192	struct device_node *np = pdev->dev.of_node;
193	u32 val;
194
195	if (!np)
196		return 0;
197	hw->bitbang.ctlr->dev.of_node = pdev->dev.of_node;
198	if (!of_property_read_u32(np, "clock-frequency", &val))
199		hw->freq = val;
200	if (!of_property_read_u32(np, "baud-width", &val))
201		hw->baudwidth = val;
202	return 0;
203}
204#else /* !CONFIG_OF */
205static int tiny_spi_of_probe(struct platform_device *pdev)
206{
207	return 0;
208}
209#endif /* CONFIG_OF */
210
211static int tiny_spi_probe(struct platform_device *pdev)
212{
213	struct tiny_spi_platform_data *platp = dev_get_platdata(&pdev->dev);
214	struct tiny_spi *hw;
215	struct spi_controller *host;
216	int err = -ENODEV;
217
218	host = spi_alloc_host(&pdev->dev, sizeof(struct tiny_spi));
219	if (!host)
220		return err;
221
222	/* setup the host state. */
223	host->bus_num = pdev->id;
224	host->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
225	host->setup = tiny_spi_setup;
226	host->use_gpio_descriptors = true;
227
228	hw = spi_controller_get_devdata(host);
229	platform_set_drvdata(pdev, hw);
230
231	/* setup the state for the bitbang driver */
232	hw->bitbang.ctlr = host;
233	hw->bitbang.setup_transfer = tiny_spi_setup_transfer;
234	hw->bitbang.txrx_bufs = tiny_spi_txrx_bufs;
235
236	/* find and map our resources */
237	hw->base = devm_platform_ioremap_resource(pdev, 0);
238	if (IS_ERR(hw->base)) {
239		err = PTR_ERR(hw->base);
240		goto exit;
241	}
242	/* irq is optional */
243	hw->irq = platform_get_irq(pdev, 0);
244	if (hw->irq >= 0) {
245		init_completion(&hw->done);
246		err = devm_request_irq(&pdev->dev, hw->irq, tiny_spi_irq, 0,
247				       pdev->name, hw);
248		if (err)
249			goto exit;
250	}
251	/* find platform data */
252	if (platp) {
253		hw->freq = platp->freq;
254		hw->baudwidth = platp->baudwidth;
255	} else {
256		err = tiny_spi_of_probe(pdev);
257		if (err)
258			goto exit;
259	}
260
261	/* register our spi controller */
262	err = spi_bitbang_start(&hw->bitbang);
263	if (err)
264		goto exit;
265	dev_info(&pdev->dev, "base %p, irq %d\n", hw->base, hw->irq);
266
267	return 0;
268
269exit:
270	spi_controller_put(host);
271	return err;
272}
273
274static void tiny_spi_remove(struct platform_device *pdev)
275{
276	struct tiny_spi *hw = platform_get_drvdata(pdev);
277	struct spi_controller *host = hw->bitbang.ctlr;
278
279	spi_bitbang_stop(&hw->bitbang);
280	spi_controller_put(host);
281}
282
283#ifdef CONFIG_OF
284static const struct of_device_id tiny_spi_match[] = {
285	{ .compatible = "opencores,tiny-spi-rtlsvn2", },
286	{},
287};
288MODULE_DEVICE_TABLE(of, tiny_spi_match);
289#endif /* CONFIG_OF */
290
291static struct platform_driver tiny_spi_driver = {
292	.probe = tiny_spi_probe,
293	.remove_new = tiny_spi_remove,
294	.driver = {
295		.name = DRV_NAME,
296		.pm = NULL,
297		.of_match_table = of_match_ptr(tiny_spi_match),
298	},
299};
300module_platform_driver(tiny_spi_driver);
301
302MODULE_DESCRIPTION("OpenCores tiny SPI driver");
303MODULE_AUTHOR("Thomas Chou <thomas@wytron.com.tw>");
304MODULE_LICENSE("GPL");
305MODULE_ALIAS("platform:" DRV_NAME);
306