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Linux/drivers/spi/spi-oc-tiny.c

  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 
 40 struct 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 
 60 static inline struct tiny_spi *tiny_spi_to_hw(struct spi_device *sdev)
 61 {
 62         return spi_master_get_devdata(sdev->master);
 63 }
 64 
 65 static 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 
 72 static 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 
 82 static 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 
 97 static 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 
109 static 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 
116 static 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 
123 static 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 
174 static 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 
205 static 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         u32 val;
211 
212         if (!np)
213                 return 0;
214         hw->gpio_cs_count = of_gpio_count(np);
215         if (hw->gpio_cs_count > 0) {
216                 hw->gpio_cs = devm_kzalloc(&pdev->dev,
217                                 hw->gpio_cs_count * sizeof(unsigned int),
218                                 GFP_KERNEL);
219                 if (!hw->gpio_cs)
220                         return -ENOMEM;
221         }
222         for (i = 0; i < hw->gpio_cs_count; i++) {
223                 hw->gpio_cs[i] = of_get_gpio_flags(np, i, NULL);
224                 if (hw->gpio_cs[i] < 0)
225                         return -ENODEV;
226         }
227         hw->bitbang.master->dev.of_node = pdev->dev.of_node;
228         if (!of_property_read_u32(np, "clock-frequency", &val))
229                 hw->freq = val;
230         if (!of_property_read_u32(np, "baud-width", &val))
231                 hw->baudwidth = val;
232         return 0;
233 }
234 #else /* !CONFIG_OF */
235 static int tiny_spi_of_probe(struct platform_device *pdev)
236 {
237         return 0;
238 }
239 #endif /* CONFIG_OF */
240 
241 static int tiny_spi_probe(struct platform_device *pdev)
242 {
243         struct tiny_spi_platform_data *platp = dev_get_platdata(&pdev->dev);
244         struct tiny_spi *hw;
245         struct spi_master *master;
246         struct resource *res;
247         unsigned int i;
248         int err = -ENODEV;
249 
250         master = spi_alloc_master(&pdev->dev, sizeof(struct tiny_spi));
251         if (!master)
252                 return err;
253 
254         /* setup the master state. */
255         master->bus_num = pdev->id;
256         master->num_chipselect = 255;
257         master->mode_bits = SPI_CPOL | SPI_CPHA | SPI_CS_HIGH;
258         master->setup = tiny_spi_setup;
259 
260         hw = spi_master_get_devdata(master);
261         platform_set_drvdata(pdev, hw);
262 
263         /* setup the state for the bitbang driver */
264         hw->bitbang.master = master;
265         hw->bitbang.setup_transfer = tiny_spi_setup_transfer;
266         hw->bitbang.chipselect = tiny_spi_chipselect;
267         hw->bitbang.txrx_bufs = tiny_spi_txrx_bufs;
268 
269         /* find and map our resources */
270         res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
271         hw->base = devm_ioremap_resource(&pdev->dev, res);
272         if (IS_ERR(hw->base)) {
273                 err = PTR_ERR(hw->base);
274                 goto exit;
275         }
276         /* irq is optional */
277         hw->irq = platform_get_irq(pdev, 0);
278         if (hw->irq >= 0) {
279                 init_completion(&hw->done);
280                 err = devm_request_irq(&pdev->dev, hw->irq, tiny_spi_irq, 0,
281                                        pdev->name, hw);
282                 if (err)
283                         goto exit;
284         }
285         /* find platform data */
286         if (platp) {
287                 hw->gpio_cs_count = platp->gpio_cs_count;
288                 hw->gpio_cs = platp->gpio_cs;
289                 if (platp->gpio_cs_count && !platp->gpio_cs) {
290                         err = -EBUSY;
291                         goto exit;
292                 }
293                 hw->freq = platp->freq;
294                 hw->baudwidth = platp->baudwidth;
295         } else {
296                 err = tiny_spi_of_probe(pdev);
297                 if (err)
298                         goto exit;
299         }
300         for (i = 0; i < hw->gpio_cs_count; i++) {
301                 err = gpio_request(hw->gpio_cs[i], dev_name(&pdev->dev));
302                 if (err)
303                         goto exit_gpio;
304                 gpio_direction_output(hw->gpio_cs[i], 1);
305         }
306         hw->bitbang.master->num_chipselect = max(1, hw->gpio_cs_count);
307 
308         /* register our spi controller */
309         err = spi_bitbang_start(&hw->bitbang);
310         if (err)
311                 goto exit;
312         dev_info(&pdev->dev, "base %p, irq %d\n", hw->base, hw->irq);
313 
314         return 0;
315 
316 exit_gpio:
317         while (i-- > 0)
318                 gpio_free(hw->gpio_cs[i]);
319 exit:
320         spi_master_put(master);
321         return err;
322 }
323 
324 static int tiny_spi_remove(struct platform_device *pdev)
325 {
326         struct tiny_spi *hw = platform_get_drvdata(pdev);
327         struct spi_master *master = hw->bitbang.master;
328         unsigned int i;
329 
330         spi_bitbang_stop(&hw->bitbang);
331         for (i = 0; i < hw->gpio_cs_count; i++)
332                 gpio_free(hw->gpio_cs[i]);
333         spi_master_put(master);
334         return 0;
335 }
336 
337 #ifdef CONFIG_OF
338 static const struct of_device_id tiny_spi_match[] = {
339         { .compatible = "opencores,tiny-spi-rtlsvn2", },
340         {},
341 };
342 MODULE_DEVICE_TABLE(of, tiny_spi_match);
343 #endif /* CONFIG_OF */
344 
345 static struct platform_driver tiny_spi_driver = {
346         .probe = tiny_spi_probe,
347         .remove = tiny_spi_remove,
348         .driver = {
349                 .name = DRV_NAME,
350                 .pm = NULL,
351                 .of_match_table = of_match_ptr(tiny_spi_match),
352         },
353 };
354 module_platform_driver(tiny_spi_driver);
355 
356 MODULE_DESCRIPTION("OpenCores tiny SPI driver");
357 MODULE_AUTHOR("Thomas Chou <thomas@wytron.com.tw>");
358 MODULE_LICENSE("GPL");
359 MODULE_ALIAS("platform:" DRV_NAME);
360 

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