drivers/spi/spi-at91-usart.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 //
   3 // Driver for AT91 USART Controllers as SPI
   4 //
   5 // Copyright (C) 2018 Microchip Technology Inc.
   6 //
   7 // Author: Radu Pirea <radu.pirea@microchip.com>
   8
   9 #include <linux/clk.h>
  10 #include <linux/delay.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/kernel.h>
  13 #include <linux/module.h>
  14 #include <linux/of_gpio.h>
  15 #include <linux/pinctrl/consumer.h>
  16 #include <linux/platform_device.h>
  17 #include <linux/pm_runtime.h>
  18
  19 #include <linux/spi/spi.h>
  20
  21 #define US_CR                   0x00
  22 #define US_MR                   0x04
  23 #define US_IER                  0x08
  24 #define US_IDR                  0x0C
  25 #define US_CSR                  0x14
  26 #define US_RHR                  0x18
  27 #define US_THR                  0x1C
  28 #define US_BRGR                 0x20
  29 #define US_VERSION              0xFC
  30
  31 #define US_CR_RSTRX             BIT(2)
  32 #define US_CR_RSTTX             BIT(3)
  33 #define US_CR_RXEN              BIT(4)
  34 #define US_CR_RXDIS             BIT(5)
  35 #define US_CR_TXEN              BIT(6)
  36 #define US_CR_TXDIS             BIT(7)
  37
  38 #define US_MR_SPI_MASTER        0x0E
  39 #define US_MR_CHRL              GENMASK(7, 6)
  40 #define US_MR_CPHA              BIT(8)
  41 #define US_MR_CPOL              BIT(16)
  42 #define US_MR_CLKO              BIT(18)
  43 #define US_MR_WRDBT             BIT(20)
  44 #define US_MR_LOOP              BIT(15)
  45
  46 #define US_IR_RXRDY             BIT(0)
  47 #define US_IR_TXRDY             BIT(1)
  48 #define US_IR_OVRE              BIT(5)
  49
  50 #define US_BRGR_SIZE            BIT(16)
  51
  52 #define US_MIN_CLK_DIV          0x06
  53 #define US_MAX_CLK_DIV          BIT(16)
  54
  55 #define US_RESET                (US_CR_RSTRX | US_CR_RSTTX)
  56 #define US_DISABLE              (US_CR_RXDIS | US_CR_TXDIS)
  57 #define US_ENABLE               (US_CR_RXEN | US_CR_TXEN)
  58 #define US_OVRE_RXRDY_IRQS      (US_IR_OVRE | US_IR_RXRDY)
  59
  60 #define US_INIT \
  61         (US_MR_SPI_MASTER | US_MR_CHRL | US_MR_CLKO | US_MR_WRDBT)
  62
  63 /* Register access macros */
  64 #define at91_usart_spi_readl(port, reg) \
  65         readl_relaxed((port)->regs + US_##reg)
  66 #define at91_usart_spi_writel(port, reg, value) \
  67         writel_relaxed((value), (port)->regs + US_##reg)
  68
  69 #define at91_usart_spi_readb(port, reg) \
  70         readb_relaxed((port)->regs + US_##reg)
  71 #define at91_usart_spi_writeb(port, reg, value) \
  72         writeb_relaxed((value), (port)->regs + US_##reg)
  73
  74 struct at91_usart_spi {
  75         struct spi_transfer     *current_transfer;
  76         void __iomem            *regs;
  77         struct device           *dev;
  78         struct clk              *clk;
  79
  80         /*used in interrupt to protect data reading*/
  81         spinlock_t              lock;
  82
  83         int                     irq;
  84         unsigned int            current_tx_remaining_bytes;
  85         unsigned int            current_rx_remaining_bytes;
  86
  87         u32                     spi_clk;
  88         u32                     status;
  89
  90         bool                    xfer_failed;
  91 };
  92
  93 static inline u32 at91_usart_spi_tx_ready(struct at91_usart_spi *aus)
  94 {
  95         return aus->status & US_IR_TXRDY;
  96 }
  97
  98 static inline u32 at91_usart_spi_rx_ready(struct at91_usart_spi *aus)
  99 {
 100         return aus->status & US_IR_RXRDY;
 101 }
 102
 103 static inline u32 at91_usart_spi_check_overrun(struct at91_usart_spi *aus)
 104 {
 105         return aus->status & US_IR_OVRE;
 106 }
 107
 108 static inline u32 at91_usart_spi_read_status(struct at91_usart_spi *aus)
 109 {
 110         aus->status = at91_usart_spi_readl(aus, CSR);
 111         return aus->status;
 112 }
 113
 114 static inline void at91_usart_spi_tx(struct at91_usart_spi *aus)
 115 {
 116         unsigned int len = aus->current_transfer->len;
 117         unsigned int remaining = aus->current_tx_remaining_bytes;
 118         const u8  *tx_buf = aus->current_transfer->tx_buf;
 119
 120         if (!remaining)
 121                 return;
 122
 123         if (at91_usart_spi_tx_ready(aus)) {
 124                 at91_usart_spi_writeb(aus, THR, tx_buf[len - remaining]);
 125                 aus->current_tx_remaining_bytes--;
 126         }
 127 }
 128
 129 static inline void at91_usart_spi_rx(struct at91_usart_spi *aus)
 130 {
 131         int len = aus->current_transfer->len;
 132         int remaining = aus->current_rx_remaining_bytes;
 133         u8  *rx_buf = aus->current_transfer->rx_buf;
 134
 135         if (!remaining)
 136                 return;
 137
 138         rx_buf[len - remaining] = at91_usart_spi_readb(aus, RHR);
 139         aus->current_rx_remaining_bytes--;
 140 }
 141
 142 static inline void
 143 at91_usart_spi_set_xfer_speed(struct at91_usart_spi *aus,
 144                               struct spi_transfer *xfer)
 145 {
 146         at91_usart_spi_writel(aus, BRGR,
 147                               DIV_ROUND_UP(aus->spi_clk, xfer->speed_hz));
 148 }
 149
 150 static irqreturn_t at91_usart_spi_interrupt(int irq, void *dev_id)
 151 {
 152         struct spi_controller *controller = dev_id;
 153         struct at91_usart_spi *aus = spi_master_get_devdata(controller);
 154
 155         spin_lock(&aus->lock);
 156         at91_usart_spi_read_status(aus);
 157
 158         if (at91_usart_spi_check_overrun(aus)) {
 159                 aus->xfer_failed = true;
 160                 at91_usart_spi_writel(aus, IDR, US_IR_OVRE | US_IR_RXRDY);
 161                 spin_unlock(&aus->lock);
 162                 return IRQ_HANDLED;
 163         }
 164
 165         if (at91_usart_spi_rx_ready(aus)) {
 166                 at91_usart_spi_rx(aus);
 167                 spin_unlock(&aus->lock);
 168                 return IRQ_HANDLED;
 169         }
 170
 171         spin_unlock(&aus->lock);
 172
 173         return IRQ_NONE;
 174 }
 175
 176 static int at91_usart_spi_setup(struct spi_device *spi)
 177 {
 178         struct at91_usart_spi *aus = spi_master_get_devdata(spi->controller);
 179         u32 *ausd = spi->controller_state;
 180         unsigned int mr = at91_usart_spi_readl(aus, MR);
 181         u8 bits = spi->bits_per_word;
 182
 183         if (bits != 8) {
 184                 dev_dbg(&spi->dev, "Only 8 bits per word are supported\n");
 185                 return -EINVAL;
 186         }
 187
 188         if (spi->mode & SPI_CPOL)
 189                 mr |= US_MR_CPOL;
 190         else
 191                 mr &= ~US_MR_CPOL;
 192
 193         if (spi->mode & SPI_CPHA)
 194                 mr |= US_MR_CPHA;
 195         else
 196                 mr &= ~US_MR_CPHA;
 197
 198         if (spi->mode & SPI_LOOP)
 199                 mr |= US_MR_LOOP;
 200         else
 201                 mr &= ~US_MR_LOOP;
 202
 203         if (!ausd) {
 204                 ausd = kzalloc(sizeof(*ausd), GFP_KERNEL);
 205                 if (!ausd)
 206                         return -ENOMEM;
 207
 208                 spi->controller_state = ausd;
 209         }
 210
 211         *ausd = mr;
 212
 213         dev_dbg(&spi->dev,
 214                 "setup: bpw %u mode 0x%x -> mr %d %08x\n",
 215                 bits, spi->mode, spi->chip_select, mr);
 216
 217         return 0;
 218 }
 219
 220 static int at91_usart_spi_transfer_one(struct spi_controller *ctlr,
 221                                        struct spi_device *spi,
 222                                        struct spi_transfer *xfer)
 223 {
 224         struct at91_usart_spi *aus = spi_master_get_devdata(ctlr);
 225
 226         at91_usart_spi_set_xfer_speed(aus, xfer);
 227         aus->xfer_failed = false;
 228         aus->current_transfer = xfer;
 229         aus->current_tx_remaining_bytes = xfer->len;
 230         aus->current_rx_remaining_bytes = xfer->len;
 231
 232         while ((aus->current_tx_remaining_bytes ||
 233                 aus->current_rx_remaining_bytes) && !aus->xfer_failed) {
 234                 at91_usart_spi_read_status(aus);
 235                 at91_usart_spi_tx(aus);
 236                 cpu_relax();
 237         }
 238
 239         if (aus->xfer_failed) {
 240                 dev_err(aus->dev, "Overrun!\n");
 241                 return -EIO;
 242         }
 243
 244         return 0;
 245 }
 246
 247 static int at91_usart_spi_prepare_message(struct spi_controller *ctlr,
 248                                           struct spi_message *message)
 249 {
 250         struct at91_usart_spi *aus = spi_master_get_devdata(ctlr);
 251         struct spi_device *spi = message->spi;
 252         u32 *ausd = spi->controller_state;
 253
 254         at91_usart_spi_writel(aus, CR, US_ENABLE);
 255         at91_usart_spi_writel(aus, IER, US_OVRE_RXRDY_IRQS);
 256         at91_usart_spi_writel(aus, MR, *ausd);
 257
 258         return 0;
 259 }
 260
 261 static int at91_usart_spi_unprepare_message(struct spi_controller *ctlr,
 262                                             struct spi_message *message)
 263 {
 264         struct at91_usart_spi *aus = spi_master_get_devdata(ctlr);
 265
 266         at91_usart_spi_writel(aus, CR, US_RESET | US_DISABLE);
 267         at91_usart_spi_writel(aus, IDR, US_OVRE_RXRDY_IRQS);
 268
 269         return 0;
 270 }
 271
 272 static void at91_usart_spi_cleanup(struct spi_device *spi)
 273 {
 274         struct at91_usart_spi_device *ausd = spi->controller_state;
 275
 276         spi->controller_state = NULL;
 277         kfree(ausd);
 278 }
 279
 280 static void at91_usart_spi_init(struct at91_usart_spi *aus)
 281 {
 282         at91_usart_spi_writel(aus, MR, US_INIT);
 283         at91_usart_spi_writel(aus, CR, US_RESET | US_DISABLE);
 284 }
 285
 286 static int at91_usart_gpio_setup(struct platform_device *pdev)
 287 {
 288         struct device_node *np = pdev->dev.parent->of_node;
 289         int i;
 290         int ret;
 291         int nb;
 292
 293         if (!np)
 294                 return -EINVAL;
 295
 296         nb = of_gpio_named_count(np, "cs-gpios");
 297         for (i = 0; i < nb; i++) {
 298                 int cs_gpio = of_get_named_gpio(np, "cs-gpios", i);
 299
 300                 if (cs_gpio < 0)
 301                         return cs_gpio;
 302
 303                 if (gpio_is_valid(cs_gpio)) {
 304                         ret = devm_gpio_request_one(&pdev->dev, cs_gpio,
 305                                                     GPIOF_DIR_OUT,
 306                                                     dev_name(&pdev->dev));
 307                         if (ret)
 308                                 return ret;
 309                 }
 310         }
 311
 312         return 0;
 313 }
 314
 315 static int at91_usart_spi_probe(struct platform_device *pdev)
 316 {
 317         struct resource *regs;
 318         struct spi_controller *controller;
 319         struct at91_usart_spi *aus;
 320         struct clk *clk;
 321         int irq;
 322         int ret;
 323
 324         regs = platform_get_resource(to_platform_device(pdev->dev.parent),
 325                                      IORESOURCE_MEM, 0);
 326         if (!regs)
 327                 return -EINVAL;
 328
 329         irq = platform_get_irq(to_platform_device(pdev->dev.parent), 0);
 330         if (irq < 0)
 331                 return irq;
 332
 333         clk = devm_clk_get(pdev->dev.parent, "usart");
 334         if (IS_ERR(clk))
 335                 return PTR_ERR(clk);
 336
 337         ret = -ENOMEM;
 338         controller = spi_alloc_master(&pdev->dev, sizeof(*aus));
 339         if (!controller)
 340                 goto at91_usart_spi_probe_fail;
 341
 342         ret = at91_usart_gpio_setup(pdev);
 343         if (ret)
 344                 goto at91_usart_spi_probe_fail;
 345
 346         controller->mode_bits = SPI_CPOL | SPI_CPHA | SPI_LOOP | SPI_CS_HIGH;
 347         controller->dev.of_node = pdev->dev.parent->of_node;
 348         controller->bits_per_word_mask = SPI_BPW_MASK(8);
 349         controller->setup = at91_usart_spi_setup;
 350         controller->flags = SPI_MASTER_MUST_RX | SPI_MASTER_MUST_TX;
 351         controller->transfer_one = at91_usart_spi_transfer_one;
 352         controller->prepare_message = at91_usart_spi_prepare_message;
 353         controller->unprepare_message = at91_usart_spi_unprepare_message;
 354         controller->cleanup = at91_usart_spi_cleanup;
 355         controller->max_speed_hz = DIV_ROUND_UP(clk_get_rate(clk),
 356                                                 US_MIN_CLK_DIV);
 357         controller->min_speed_hz = DIV_ROUND_UP(clk_get_rate(clk),
 358                                                 US_MAX_CLK_DIV);
 359         platform_set_drvdata(pdev, controller);
 360
 361         aus = spi_master_get_devdata(controller);
 362
 363         aus->dev = &pdev->dev;
 364         aus->regs = devm_ioremap_resource(&pdev->dev, regs);
 365         if (IS_ERR(aus->regs)) {
 366                 ret = PTR_ERR(aus->regs);
 367                 goto at91_usart_spi_probe_fail;
 368         }
 369
 370         aus->irq = irq;
 371         aus->clk = clk;
 372
 373         ret = devm_request_irq(&pdev->dev, irq, at91_usart_spi_interrupt, 0,
 374                                dev_name(&pdev->dev), controller);
 375         if (ret)
 376                 goto at91_usart_spi_probe_fail;
 377
 378         ret = clk_prepare_enable(clk);
 379         if (ret)
 380                 goto at91_usart_spi_probe_fail;
 381
 382         aus->spi_clk = clk_get_rate(clk);
 383         at91_usart_spi_init(aus);
 384
 385         spin_lock_init(&aus->lock);
 386         ret = devm_spi_register_master(&pdev->dev, controller);
 387         if (ret)
 388                 goto at91_usart_fail_register_master;
 389
 390         dev_info(&pdev->dev,
 391                  "AT91 USART SPI Controller version 0x%x at %pa (irq %d)\n",
 392                  at91_usart_spi_readl(aus, VERSION),
 393                  &regs->start, irq);
 394
 395         return 0;
 396
 397 at91_usart_fail_register_master:
 398         clk_disable_unprepare(clk);
 399 at91_usart_spi_probe_fail:
 400         spi_master_put(controller);
 401         return ret;
 402 }
 403
 404 __maybe_unused static int at91_usart_spi_runtime_suspend(struct device *dev)
 405 {
 406         struct spi_controller *ctlr = dev_get_drvdata(dev);
 407         struct at91_usart_spi *aus = spi_master_get_devdata(ctlr);
 408
 409         clk_disable_unprepare(aus->clk);
 410         pinctrl_pm_select_sleep_state(dev);
 411
 412         return 0;
 413 }
 414
 415 __maybe_unused static int at91_usart_spi_runtime_resume(struct device *dev)
 416 {
 417         struct spi_controller *ctrl = dev_get_drvdata(dev);
 418         struct at91_usart_spi *aus = spi_master_get_devdata(ctrl);
 419
 420         pinctrl_pm_select_default_state(dev);
 421
 422         return clk_prepare_enable(aus->clk);
 423 }
 424
 425 __maybe_unused static int at91_usart_spi_suspend(struct device *dev)
 426 {
 427         struct spi_controller *ctrl = dev_get_drvdata(dev);
 428         int ret;
 429
 430         ret = spi_controller_suspend(ctrl);
 431         if (ret)
 432                 return ret;
 433
 434         if (!pm_runtime_suspended(dev))
 435                 at91_usart_spi_runtime_suspend(dev);
 436
 437         return 0;
 438 }
 439
 440 __maybe_unused static int at91_usart_spi_resume(struct device *dev)
 441 {
 442         struct spi_controller *ctrl = dev_get_drvdata(dev);
 443         struct at91_usart_spi *aus = spi_master_get_devdata(ctrl);
 444         int ret;
 445
 446         if (!pm_runtime_suspended(dev)) {
 447                 ret = at91_usart_spi_runtime_resume(dev);
 448                 if (ret)
 449                         return ret;
 450         }
 451
 452         at91_usart_spi_init(aus);
 453
 454         return spi_controller_resume(ctrl);
 455 }
 456
 457 static int at91_usart_spi_remove(struct platform_device *pdev)
 458 {
 459         struct spi_controller *ctlr = platform_get_drvdata(pdev);
 460         struct at91_usart_spi *aus = spi_master_get_devdata(ctlr);
 461
 462         clk_disable_unprepare(aus->clk);
 463
 464         return 0;
 465 }
 466
 467 static const struct dev_pm_ops at91_usart_spi_pm_ops = {
 468         SET_SYSTEM_SLEEP_PM_OPS(at91_usart_spi_suspend, at91_usart_spi_resume)
 469         SET_RUNTIME_PM_OPS(at91_usart_spi_runtime_suspend,
 470                            at91_usart_spi_runtime_resume, NULL)
 471 };
 472
 473 static const struct of_device_id at91_usart_spi_dt_ids[] = {
 474         { .compatible = "microchip,at91sam9g45-usart-spi"},
 475         { /* sentinel */}
 476 };
 477
 478 MODULE_DEVICE_TABLE(of, at91_usart_spi_dt_ids);
 479
 480 static struct platform_driver at91_usart_spi_driver = {
 481         .driver = {
 482                 .name = "at91_usart_spi",
 483                 .pm = &at91_usart_spi_pm_ops,
 484         },
 485         .probe = at91_usart_spi_probe,
 486         .remove = at91_usart_spi_remove,
 487 };
 488
 489 module_platform_driver(at91_usart_spi_driver);
 490
 491 MODULE_DESCRIPTION("Microchip AT91 USART SPI Controller driver");
 492 MODULE_AUTHOR("Radu Pirea <radu.pirea@microchip.com>");
 493 MODULE_LICENSE("GPL v2");
 494 MODULE_ALIAS("platform:at91_usart_spi");