drivers/misc/atmel_pwm.c

   1 #include <linux/module.h>
   2 #include <linux/clk.h>
   3 #include <linux/err.h>
   4 #include <linux/io.h>
   5 #include <linux/interrupt.h>
   6 #include <linux/platform_device.h>
   7 #include <linux/atmel_pwm.h>
   8
   9
  10 /*
  11  * This is a simple driver for the PWM controller found in various newer
  12  * Atmel SOCs, including the AVR32 series and the AT91sam9263.
  13  *
  14  * Chips with current Linux ports have only 4 PWM channels, out of max 32.
  15  * AT32UC3A and AT32UC3B chips have 7 channels (but currently no Linux).
  16  * Docs are inconsistent about the width of the channel counter registers;
  17  * it's at least 16 bits, but several places say 20 bits.
  18  */
  19 #define PWM_NCHAN       4               /* max 32 */
  20
  21 struct pwm {
  22         spinlock_t              lock;
  23         struct platform_device  *pdev;
  24         u32                     mask;
  25         int                     irq;
  26         void __iomem            *base;
  27         struct clk              *clk;
  28         struct pwm_channel      *channel[PWM_NCHAN];
  29         void                    (*handler[PWM_NCHAN])(struct pwm_channel *);
  30 };
  31
  32
  33 /* global PWM controller registers */
  34 #define PWM_MR          0x00
  35 #define PWM_ENA         0x04
  36 #define PWM_DIS         0x08
  37 #define PWM_SR          0x0c
  38 #define PWM_IER         0x10
  39 #define PWM_IDR         0x14
  40 #define PWM_IMR         0x18
  41 #define PWM_ISR         0x1c
  42
  43 static inline void pwm_writel(const struct pwm *p, unsigned offset, u32 val)
  44 {
  45         __raw_writel(val, p->base + offset);
  46 }
  47
  48 static inline u32 pwm_readl(const struct pwm *p, unsigned offset)
  49 {
  50         return __raw_readl(p->base + offset);
  51 }
  52
  53 static inline void __iomem *pwmc_regs(const struct pwm *p, int index)
  54 {
  55         return p->base + 0x200 + index * 0x20;
  56 }
  57
  58 static struct pwm *pwm;
  59
  60 static void pwm_dumpregs(struct pwm_channel *ch, char *tag)
  61 {
  62         struct device   *dev = &pwm->pdev->dev;
  63
  64         dev_dbg(dev, "%s: mr %08x, sr %08x, imr %08x\n",
  65                 tag,
  66                 pwm_readl(pwm, PWM_MR),
  67                 pwm_readl(pwm, PWM_SR),
  68                 pwm_readl(pwm, PWM_IMR));
  69         dev_dbg(dev,
  70                 "pwm ch%d - mr %08x, dty %u, prd %u, cnt %u\n",
  71                 ch->index,
  72                 pwm_channel_readl(ch, PWM_CMR),
  73                 pwm_channel_readl(ch, PWM_CDTY),
  74                 pwm_channel_readl(ch, PWM_CPRD),
  75                 pwm_channel_readl(ch, PWM_CCNT));
  76 }
  77
  78
  79 /**
  80  * pwm_channel_alloc - allocate an unused PWM channel
  81  * @index: identifies the channel
  82  * @ch: structure to be initialized
  83  *
  84  * Drivers allocate PWM channels according to the board's wiring, and
  85  * matching board-specific setup code.  Returns zero or negative errno.
  86  */
  87 int pwm_channel_alloc(int index, struct pwm_channel *ch)
  88 {
  89         unsigned long   flags;
  90         int             status = 0;
  91
  92         /* insist on PWM init, with this signal pinned out */
  93         if (!pwm || !(pwm->mask & 1 << index))
  94                 return -ENODEV;
  95
  96         if (index < 0 || index >= PWM_NCHAN || !ch)
  97                 return -EINVAL;
  98         memset(ch, 0, sizeof *ch);
  99
 100         spin_lock_irqsave(&pwm->lock, flags);
 101         if (pwm->channel[index])
 102                 status = -EBUSY;
 103         else {
 104                 clk_enable(pwm->clk);
 105
 106                 ch->regs = pwmc_regs(pwm, index);
 107                 ch->index = index;
 108
 109                 /* REVISIT: ap7000 seems to go 2x as fast as we expect!! */
 110                 ch->mck = clk_get_rate(pwm->clk);
 111
 112                 pwm->channel[index] = ch;
 113                 pwm->handler[index] = NULL;
 114
 115                 /* channel and irq are always disabled when we return */
 116                 pwm_writel(pwm, PWM_DIS, 1 << index);
 117                 pwm_writel(pwm, PWM_IDR, 1 << index);
 118         }
 119         spin_unlock_irqrestore(&pwm->lock, flags);
 120         return status;
 121 }
 122 EXPORT_SYMBOL(pwm_channel_alloc);
 123
 124 static int pwmcheck(struct pwm_channel *ch)
 125 {
 126         int             index;
 127
 128         if (!pwm)
 129                 return -ENODEV;
 130         if (!ch)
 131                 return -EINVAL;
 132         index = ch->index;
 133         if (index < 0 || index >= PWM_NCHAN || pwm->channel[index] != ch)
 134                 return -EINVAL;
 135
 136         return index;
 137 }
 138
 139 /**
 140  * pwm_channel_free - release a previously allocated channel
 141  * @ch: the channel being released
 142  *
 143  * The channel is completely shut down (counter and IRQ disabled),
 144  * and made available for re-use.  Returns zero, or negative errno.
 145  */
 146 int pwm_channel_free(struct pwm_channel *ch)
 147 {
 148         unsigned long   flags;
 149         int             t;
 150
 151         spin_lock_irqsave(&pwm->lock, flags);
 152         t = pwmcheck(ch);
 153         if (t >= 0) {
 154                 pwm->channel[t] = NULL;
 155                 pwm->handler[t] = NULL;
 156
 157                 /* channel and irq are always disabled when we return */
 158                 pwm_writel(pwm, PWM_DIS, 1 << t);
 159                 pwm_writel(pwm, PWM_IDR, 1 << t);
 160
 161                 clk_disable(pwm->clk);
 162                 t = 0;
 163         }
 164         spin_unlock_irqrestore(&pwm->lock, flags);
 165         return t;
 166 }
 167 EXPORT_SYMBOL(pwm_channel_free);
 168
 169 int __pwm_channel_onoff(struct pwm_channel *ch, int enabled)
 170 {
 171         unsigned long   flags;
 172         int             t;
 173
 174         /* OMITTED FUNCTIONALITY:  starting several channels in synch */
 175
 176         spin_lock_irqsave(&pwm->lock, flags);
 177         t = pwmcheck(ch);
 178         if (t >= 0) {
 179                 pwm_writel(pwm, enabled ? PWM_ENA : PWM_DIS, 1 << t);
 180                 t = 0;
 181                 pwm_dumpregs(ch, enabled ? "enable" : "disable");
 182         }
 183         spin_unlock_irqrestore(&pwm->lock, flags);
 184
 185         return t;
 186 }
 187 EXPORT_SYMBOL(__pwm_channel_onoff);
 188
 189 /**
 190  * pwm_clk_alloc - allocate and configure CLKA or CLKB
 191  * @prescale: from 0..10, the power of two used to divide MCK
 192  * @div: from 1..255, the linear divisor to use
 193  *
 194  * Returns PWM_CPR_CLKA, PWM_CPR_CLKB, or negative errno.  The allocated
 195  * clock will run with a period of (2^prescale * div) / MCK, or twice as
 196  * long if center aligned PWM output is used.  The clock must later be
 197  * deconfigured using pwm_clk_free().
 198  */
 199 int pwm_clk_alloc(unsigned prescale, unsigned div)
 200 {
 201         unsigned long   flags;
 202         u32             mr;
 203         u32             val = (prescale << 8) | div;
 204         int             ret = -EBUSY;
 205
 206         if (prescale >= 10 || div == 0 || div > 255)
 207                 return -EINVAL;
 208
 209         spin_lock_irqsave(&pwm->lock, flags);
 210         mr = pwm_readl(pwm, PWM_MR);
 211         if ((mr & 0xffff) == 0) {
 212                 mr |= val;
 213                 ret = PWM_CPR_CLKA;
 214         }
 215         if ((mr & (0xffff << 16)) == 0) {
 216                 mr |= val << 16;
 217                 ret = PWM_CPR_CLKB;
 218         }
 219         if (ret > 0)
 220                 pwm_writel(pwm, PWM_MR, mr);
 221         spin_unlock_irqrestore(&pwm->lock, flags);
 222         return ret;
 223 }
 224 EXPORT_SYMBOL(pwm_clk_alloc);
 225
 226 /**
 227  * pwm_clk_free - deconfigure and release CLKA or CLKB
 228  *
 229  * Reverses the effect of pwm_clk_alloc().
 230  */
 231 void pwm_clk_free(unsigned clk)
 232 {
 233         unsigned long   flags;
 234         u32             mr;
 235
 236         spin_lock_irqsave(&pwm->lock, flags);
 237         mr = pwm_readl(pwm, PWM_MR);
 238         if (clk == PWM_CPR_CLKA)
 239                 pwm_writel(pwm, PWM_MR, mr & ~(0xffff << 0));
 240         if (clk == PWM_CPR_CLKB)
 241                 pwm_writel(pwm, PWM_MR, mr & ~(0xffff << 16));
 242         spin_unlock_irqrestore(&pwm->lock, flags);
 243 }
 244 EXPORT_SYMBOL(pwm_clk_free);
 245
 246 /**
 247  * pwm_channel_handler - manage channel's IRQ handler
 248  * @ch: the channel
 249  * @handler: the handler to use, possibly NULL
 250  *
 251  * If the handler is non-null, the handler will be called after every
 252  * period of this PWM channel.  If the handler is null, this channel
 253  * won't generate an IRQ.
 254  */
 255 int pwm_channel_handler(struct pwm_channel *ch,
 256                 void (*handler)(struct pwm_channel *ch))
 257 {
 258         unsigned long   flags;
 259         int             t;
 260
 261         spin_lock_irqsave(&pwm->lock, flags);
 262         t = pwmcheck(ch);
 263         if (t >= 0) {
 264                 pwm->handler[t] = handler;
 265                 pwm_writel(pwm, handler ? PWM_IER : PWM_IDR, 1 << t);
 266                 t = 0;
 267         }
 268         spin_unlock_irqrestore(&pwm->lock, flags);
 269
 270         return t;
 271 }
 272 EXPORT_SYMBOL(pwm_channel_handler);
 273
 274 static irqreturn_t pwm_irq(int id, void *_pwm)
 275 {
 276         struct pwm      *p = _pwm;
 277         irqreturn_t     handled = IRQ_NONE;
 278         u32             irqstat;
 279         int             index;
 280
 281         spin_lock(&p->lock);
 282
 283         /* ack irqs, then handle them */
 284         irqstat = pwm_readl(pwm, PWM_ISR);
 285
 286         while (irqstat) {
 287                 struct pwm_channel *ch;
 288                 void (*handler)(struct pwm_channel *ch);
 289
 290                 index = ffs(irqstat) - 1;
 291                 irqstat &= ~(1 << index);
 292                 ch = pwm->channel[index];
 293                 handler = pwm->handler[index];
 294                 if (handler && ch) {
 295                         spin_unlock(&p->lock);
 296                         handler(ch);
 297                         spin_lock(&p->lock);
 298                         handled = IRQ_HANDLED;
 299                 }
 300         }
 301
 302         spin_unlock(&p->lock);
 303         return handled;
 304 }
 305
 306 static int __init pwm_probe(struct platform_device *pdev)
 307 {
 308         struct resource *r = platform_get_resource(pdev, IORESOURCE_MEM, 0);
 309         int irq = platform_get_irq(pdev, 0);
 310         u32 *mp = pdev->dev.platform_data;
 311         struct pwm *p;
 312         int status = -EIO;
 313
 314         if (pwm)
 315                 return -EBUSY;
 316         if (!r || irq < 0 || !mp || !*mp)
 317                 return -ENODEV;
 318         if (*mp & ~((1<<PWM_NCHAN)-1)) {
 319                 dev_warn(&pdev->dev, "mask 0x%x ... more than %d channels\n",
 320                         *mp, PWM_NCHAN);
 321                 return -EINVAL;
 322         }
 323
 324         p = kzalloc(sizeof(*p), GFP_KERNEL);
 325         if (!p)
 326                 return -ENOMEM;
 327
 328         spin_lock_init(&p->lock);
 329         p->pdev = pdev;
 330         p->mask = *mp;
 331         p->irq = irq;
 332         p->base = ioremap(r->start, r->end - r->start + 1);
 333         if (!p->base)
 334                 goto fail;
 335         p->clk = clk_get(&pdev->dev, "mck");
 336         if (IS_ERR(p->clk)) {
 337                 status = PTR_ERR(p->clk);
 338                 p->clk = NULL;
 339                 goto fail;
 340         }
 341
 342         status = request_irq(irq, pwm_irq, 0, pdev->name, p);
 343         if (status < 0)
 344                 goto fail;
 345
 346         pwm = p;
 347         platform_set_drvdata(pdev, p);
 348
 349         return 0;
 350
 351 fail:
 352         if (p->clk)
 353                 clk_put(p->clk);
 354         if (p->base)
 355                 iounmap(p->base);
 356
 357         kfree(p);
 358         return status;
 359 }
 360
 361 static int __exit pwm_remove(struct platform_device *pdev)
 362 {
 363         struct pwm *p = platform_get_drvdata(pdev);
 364
 365         if (p != pwm)
 366                 return -EINVAL;
 367
 368         clk_enable(pwm->clk);
 369         pwm_writel(pwm, PWM_DIS, (1 << PWM_NCHAN) - 1);
 370         pwm_writel(pwm, PWM_IDR, (1 << PWM_NCHAN) - 1);
 371         clk_disable(pwm->clk);
 372
 373         pwm = NULL;
 374
 375         free_irq(p->irq, p);
 376         clk_put(p->clk);
 377         iounmap(p->base);
 378         kfree(p);
 379
 380         return 0;
 381 }
 382
 383 static struct platform_driver atmel_pwm_driver = {
 384         .driver = {
 385                 .name = "atmel_pwm",
 386                 .owner = THIS_MODULE,
 387         },
 388         .remove = __exit_p(pwm_remove),
 389
 390         /* NOTE: PWM can keep running in AVR32 "idle" and "frozen" states;
 391          * and all AT91sam9263 states, albeit at reduced clock rate if
 392          * MCK becomes the slow clock (i.e. what Linux labels STR).
 393          */
 394 };
 395
 396 static int __init pwm_init(void)
 397 {
 398         return platform_driver_probe(&atmel_pwm_driver, pwm_probe);
 399 }
 400 module_init(pwm_init);
 401
 402 static void __exit pwm_exit(void)
 403 {
 404         platform_driver_unregister(&atmel_pwm_driver);
 405 }
 406 module_exit(pwm_exit);
 407
 408 MODULE_DESCRIPTION("Driver for AT32/AT91 PWM module");
 409 MODULE_LICENSE("GPL");