1/*
2 * OpenCores tiny SPI master driver
3 *
4 * http://opencores.org/project,tiny_spi
5 *
6 * Copyright (C) 2011 Thomas Chou <thomas@wytron.com.tw>
7 *
8 * Based on spi_s3c24xx.c, which is:
9 * Copyright (c) 2006 Ben Dooks
10 * Copyright (c) 2006 Simtec Electronics
11 *	Ben Dooks <ben@simtec.co.uk>
12 *
13 * This program is free software; you can redistribute it and/or modify
14 * it under the terms of the GNU General Public License version 2 as
15 * published by the Free Software Foundation.
16 */
17
18#include <linux/interrupt.h>
19#include <linux/errno.h>
20#include <linux/module.h>
21#include <linux/platform_device.h>
22#include <linux/spi/spi.h>
23#include <linux/spi/spi_bitbang.h>
24#include <linux/spi/spi_oc_tiny.h>
25#include <linux/io.h>
26#include <linux/gpio.h>
27#include <linux/of.h>
28
29#define DRV_NAME "spi_oc_tiny"
30
31#define TINY_SPI_RXDATA 0
32#define TINY_SPI_TXDATA 4
33#define TINY_SPI_STATUS 8
34#define TINY_SPI_CONTROL 12
35#define TINY_SPI_BAUD 16
36
37#define TINY_SPI_STATUS_TXE 0x1
38#define TINY_SPI_STATUS_TXR 0x2
39
40struct tiny_spi {
41	/* bitbang has to be first */
42	struct spi_bitbang bitbang;
43	struct completion done;
44
45	void __iomem *base;
46	int irq;
47	unsigned int freq;
48	unsigned int baudwidth;
49	unsigned int baud;
50	unsigned int speed_hz;
51	unsigned int mode;
52	unsigned int len;
53	unsigned int txc, rxc;
54	const u8 *txp;
55	u8 *rxp;
56	int gpio_cs_count;
57	int *gpio_cs;
58};
59
60static inline struct tiny_spi *tiny_spi_to_hw(struct spi_device *sdev)
61{
62	return spi_master_get_devdata(sdev->master);
63}
64
65static unsigned int tiny_spi_baud(struct spi_device *spi, unsigned int hz)
66{
67	struct tiny_spi *hw = tiny_spi_to_hw(spi);
68
69	return min(DIV_ROUND_UP(hw->freq, hz * 2), (1U << hw->baudwidth)) - 1;
70}
71
72static void tiny_spi_chipselect(struct spi_device *spi, int is_active)
73{
74	struct tiny_spi *hw = tiny_spi_to_hw(spi);
75
76	if (hw->gpio_cs_count > 0) {
77		gpio_set_value(hw->gpio_cs[spi->chip_select],
78			(spi->mode & SPI_CS_HIGH) ? is_active : !is_active);
79	}
80}
81
82static int tiny_spi_setup_transfer(struct spi_device *spi,
83				   struct spi_transfer *t)
84{
85	struct tiny_spi *hw = tiny_spi_to_hw(spi);
86	unsigned int baud = hw->baud;
87
88	if (t) {
89		if (t->speed_hz && t->speed_hz != hw->speed_hz)
90			baud = tiny_spi_baud(spi, t->speed_hz);
91	}
92	writel(baud, hw->base + TINY_SPI_BAUD);
93	writel(hw->mode, hw->base + TINY_SPI_CONTROL);
94	return 0;
95}
96
97static int tiny_spi_setup(struct spi_device *spi)
98{
99	struct tiny_spi *hw = tiny_spi_to_hw(spi);
100
101	if (spi->max_speed_hz != hw->speed_hz) {
102		hw->speed_hz = spi->max_speed_hz;
103		hw->baud = tiny_spi_baud(spi, hw->speed_hz);
104	}
105	hw->mode = spi->mode & (SPI_CPOL | SPI_CPHA);
106	return 0;
107}
108
109static inline void tiny_spi_wait_txr(struct tiny_spi *hw)
110{
111	while (!(readb(hw->base + TINY_SPI_STATUS) &
112		 TINY_SPI_STATUS_TXR))
113		cpu_relax();
114}
115
116static inline void tiny_spi_wait_txe(struct tiny_spi *hw)
117{
118	while (!(readb(hw->base + TINY_SPI_STATUS) &
119		 TINY_SPI_STATUS_TXE))
120		cpu_relax();
121}
122
123static int tiny_spi_txrx_bufs(struct spi_device *spi, struct spi_transfer *t)
124{
125	struct tiny_spi *hw = tiny_spi_to_hw(spi);
126	const u8 *txp = t->tx_buf;
127	u8 *rxp = t->rx_buf;
128	unsigned int i;
129
130	if (hw->irq >= 0) {
131		/* use interrupt driven data transfer */
132		hw->len = t->len;
133		hw->txp = t->tx_buf;
134		hw->rxp = t->rx_buf;
135		hw->txc = 0;
136		hw->rxc = 0;
137
138		/* send the first byte */
139		if (t->len > 1) {
140			writeb(hw->txp ? *hw->txp++ : 0,
141			       hw->base + TINY_SPI_TXDATA);
142			hw->txc++;
143			writeb(hw->txp ? *hw->txp++ : 0,
144			       hw->base + TINY_SPI_TXDATA);
145			hw->txc++;
146			writeb(TINY_SPI_STATUS_TXR, hw->base + TINY_SPI_STATUS);
147		} else {
148			writeb(hw->txp ? *hw->txp++ : 0,
149			       hw->base + TINY_SPI_TXDATA);
150			hw->txc++;
151			writeb(TINY_SPI_STATUS_TXE, hw->base + TINY_SPI_STATUS);
152		}
153
154		wait_for_completion(&hw->done);
155	} else {
156		/* we need to tighten the transfer loop */
157		writeb(txp ? *txp++ : 0, hw->base + TINY_SPI_TXDATA);
158		for (i = 1; i < t->len; i++) {
159			writeb(txp ? *txp++ : 0, hw->base + TINY_SPI_TXDATA);
160
161			if (rxp || (i != t->len - 1))
162				tiny_spi_wait_txr(hw);
163			if (rxp)
164				*rxp++ = readb(hw->base + TINY_SPI_TXDATA);
165		}
166		tiny_spi_wait_txe(hw);
167		if (rxp)
168			*rxp++ = readb(hw->base + TINY_SPI_RXDATA);
169	}
170
171	return t->len;
172}
173
174static irqreturn_t tiny_spi_irq(int irq, void *dev)
175{
176	struct tiny_spi *hw = dev;
177
178	writeb(0, hw->base + TINY_SPI_STATUS);
179	if (hw->rxc + 1 == hw->len) {
180		if (hw->rxp)
181			*hw->rxp++ = readb(hw->base + TINY_SPI_RXDATA);
182		hw->rxc++;
183		complete(&hw->done);
184	} else {
185		if (hw->rxp)
186			*hw->rxp++ = readb(hw->base + TINY_SPI_TXDATA);
187		hw->rxc++;
188		if (hw->txc < hw->len) {
189			writeb(hw->txp ? *hw->txp++ : 0,
190			       hw->base + TINY_SPI_TXDATA);
191			hw->txc++;
192			writeb(TINY_SPI_STATUS_TXR,
193			       hw->base + TINY_SPI_STATUS);
194		} else {
195			writeb(TINY_SPI_STATUS_TXE,
196			       hw->base + TINY_SPI_STATUS);
197		}
198	}
199	return IRQ_HANDLED;
200}
201
202#ifdef CONFIG_OF
203#include <linux/of_gpio.h>
204
205static int tiny_spi_of_probe(struct platform_device *pdev)
206{
207	struct tiny_spi *hw = platform_get_drvdata(pdev);
208	struct device_node *np = pdev->dev.of_node;
209	unsigned int i;
210	const __be32 *val;
211	int len;
212
213	if (!np)
214		return 0;
215	hw->gpio_cs_count = of_gpio_count(np);
216	if (hw->gpio_cs_count > 0) {
217		hw->gpio_cs = devm_kzalloc(&pdev->dev,
218				hw->gpio_cs_count * sizeof(unsigned int),
219				GFP_KERNEL);
220		if (!hw->gpio_cs)
221			return -ENOMEM;
222	}
223	for (i = 0; i < hw->gpio_cs_count; i++) {
224		hw->gpio_cs[i] = of_get_gpio_flags(np, i, NULL);
225		if (hw->gpio_cs[i] < 0)
226			return -ENODEV;
227	}
228	hw->bitbang.master->dev.of_node = pdev->dev.of_node;
229	val = of_get_property(pdev->dev.of_node,
230			      "clock-frequency", &len);
231	if (val && len >= sizeof(__be32))
232		hw->freq = be32_to_cpup(val);
233	val = of_get_property(pdev->dev.of_node, "baud-width", &len);
234	if (val && len >= sizeof(__be32))
235		hw->baudwidth = be32_to_cpup(val);
236	return 0;
237}
238#else /* !CONFIG_OF */
239static int tiny_spi_of_probe(struct platform_device *pdev)
240{
241	return 0;
242}
243#endif /* CONFIG_OF */
244
245static int tiny_spi_probe(struct platform_device *pdev)
246{
247	struct tiny_spi_platform_data *platp = dev_get_platdata(&pdev->dev);
248	struct tiny_spi *hw;
249	struct spi_master *master;
250	struct resource *res;
251	unsigned int i;
252	int err = -ENODEV;
253
254	master = spi_alloc_master(&pdev->dev, sizeof(struct tiny_spi));
255	if (!master)
256		return err;
257
258	/* setup the master state. */
259	master->bus_num = pdev->id;
260	master->num_chipselect = 255;
261	master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
262	master->setup = tiny_spi_setup;
263
264	hw = spi_master_get_devdata(master);
265	platform_set_drvdata(pdev, hw);
266
267	/* setup the state for the bitbang driver */
268	hw->bitbang.master = master;
269	hw->bitbang.setup_transfer = tiny_spi_setup_transfer;
270	hw->bitbang.chipselect = tiny_spi_chipselect;
271	hw->bitbang.txrx_bufs = tiny_spi_txrx_bufs;
272
273	/* find and map our resources */
274	res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
275	hw->base = devm_ioremap_resource(&pdev->dev, res);
276	if (IS_ERR(hw->base)) {
277		err = PTR_ERR(hw->base);
278		goto exit;
279	}
280	/* irq is optional */
281	hw->irq = platform_get_irq(pdev, 0);
282	if (hw->irq >= 0) {
283		init_completion(&hw->done);
284		err = devm_request_irq(&pdev->dev, hw->irq, tiny_spi_irq, 0,
285				       pdev->name, hw);
286		if (err)
287			goto exit;
288	}
289	/* find platform data */
290	if (platp) {
291		hw->gpio_cs_count = platp->gpio_cs_count;
292		hw->gpio_cs = platp->gpio_cs;
293		if (platp->gpio_cs_count && !platp->gpio_cs) {
294			err = -EBUSY;
295			goto exit;
296		}
297		hw->freq = platp->freq;
298		hw->baudwidth = platp->baudwidth;
299	} else {
300		err = tiny_spi_of_probe(pdev);
301		if (err)
302			goto exit;
303	}
304	for (i = 0; i < hw->gpio_cs_count; i++) {
305		err = gpio_request(hw->gpio_cs[i], dev_name(&pdev->dev));
306		if (err)
307			goto exit_gpio;
308		gpio_direction_output(hw->gpio_cs[i], 1);
309	}
310	hw->bitbang.master->num_chipselect = max(1, hw->gpio_cs_count);
311
312	/* register our spi controller */
313	err = spi_bitbang_start(&hw->bitbang);
314	if (err)
315		goto exit;
316	dev_info(&pdev->dev, "base %p, irq %d\n", hw->base, hw->irq);
317
318	return 0;
319
320exit_gpio:
321	while (i-- > 0)
322		gpio_free(hw->gpio_cs[i]);
323exit:
324	spi_master_put(master);
325	return err;
326}
327
328static int tiny_spi_remove(struct platform_device *pdev)
329{
330	struct tiny_spi *hw = platform_get_drvdata(pdev);
331	struct spi_master *master = hw->bitbang.master;
332	unsigned int i;
333
334	spi_bitbang_stop(&hw->bitbang);
335	for (i = 0; i < hw->gpio_cs_count; i++)
336		gpio_free(hw->gpio_cs[i]);
337	spi_master_put(master);
338	return 0;
339}
340
341#ifdef CONFIG_OF
342static const struct of_device_id tiny_spi_match[] = {
343	{ .compatible = "opencores,tiny-spi-rtlsvn2", },
344	{},
345};
346MODULE_DEVICE_TABLE(of, tiny_spi_match);
347#endif /* CONFIG_OF */
348
349static struct platform_driver tiny_spi_driver = {
350	.probe = tiny_spi_probe,
351	.remove = tiny_spi_remove,
352	.driver = {
353		.name = DRV_NAME,
354		.pm = NULL,
355		.of_match_table = of_match_ptr(tiny_spi_match),
356	},
357};
358module_platform_driver(tiny_spi_driver);
359
360MODULE_DESCRIPTION("OpenCores tiny SPI driver");
361MODULE_AUTHOR("Thomas Chou <thomas@wytron.com.tw>");
362MODULE_LICENSE("GPL");
363MODULE_ALIAS("platform:" DRV_NAME);
364