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Sourcecode: alsa-driver version File versions

pcsp_lib.c

#include "adriver.h"
/*
 * PC-Speaker driver for Linux
 *
 * Copyright (C) 1993-1997  Michael Beck
 * Copyright (C) 1997-2001  David Woodhouse
 * Copyright (C) 2001-2007  Stas Sergeev
 */

#include <sound/pcm.h>
#include <sound/pcm_params.h>
#include <linux/interrupt.h>
#include <asm/io.h>
#include <asm/i8253.h>
#include "pcsp.h"

#define DMIX_WANTS_S16  1

static void pcsp_start_timer(unsigned long dummy)
{
      hrtimer_start(&pcsp_chip.timer, ktime_set(0, 0), HRTIMER_MODE_REL);
}

/*
 * We need the hrtimer_start as a tasklet to avoid
 * the nasty locking problem. :(
 * The problem:
 * - The timer handler is called with the cpu_base->lock
 *   already held by hrtimer code.
 * - snd_pcm_period_elapsed() takes the
 *   substream->self_group.lock.
 * So far so good.
 * But the snd_pcsp_trigger() is called with the
 * substream->self_group.lock held, and it calls
 * hrtimer_start(), which takes the cpu_base->lock.
 * You see the problem. We have the code pathes
 * which take two locks in a reverse order. This
 * can deadlock and the lock validator complains.
 * The only solution I could find was to move the
 * hrtimer_start() into a tasklet. -stsp
 */
DECLARE_TASKLET(pcsp_start_timer_tasklet, pcsp_start_timer, 0);

enum hrtimer_restart pcsp_do_timer(struct hrtimer *handle)
{
      unsigned long flags;
      unsigned char timer_cnt, val;
      int fmt_size, periods_elapsed;
      size_t period_bytes, buffer_bytes;
      struct snd_pcm_substream *substream;
      struct snd_pcm_runtime *runtime;
      struct snd_pcsp *chip = container_of(handle, struct snd_pcsp, timer);

      /* hrtimer calls us from both hardirq and softirq contexts,
       * so irqsave :( */
      spin_lock_irqsave(&chip->substream_lock, flags);
      /* Takashi Iwai says regarding this extra lock:

      If the irq handler handles some data on the DMA buffer, it should
      do snd_pcm_stream_lock().
      That protects basically against all races among PCM callbacks, yes.
      However, there are two remaining issues:
      1. The substream pointer you try to lock isn't protected _before_
        this lock yet.
      2. snd_pcm_period_elapsed() itself acquires the lock.
      The requirement of another lock is because of 1.  When you get
      chip->playback_substream, it's not protected.
      Keeping this lock while snd_pcm_period_elapsed() assures the substream
      is still protected (at least, not released).  And the other status is
      handled properly inside snd_pcm_stream_lock() in
      snd_pcm_period_elapsed().

      */
      if (!chip->playback_substream)
            goto exit_nr_unlock1;
      substream = chip->playback_substream;
      snd_pcm_stream_lock(substream);
      if (!chip->timer_active)
            goto exit_nr_unlock2;

      runtime = substream->runtime;
      fmt_size = snd_pcm_format_physical_width(runtime->format) >> 3;
      /* assume it is mono! */
      val = runtime->dma_area[chip->playback_ptr + fmt_size - 1];
      if (snd_pcm_format_signed(runtime->format))
            val ^= 0x80;
      timer_cnt = val * CUR_DIV() / 256;

      if (timer_cnt && chip->enable) {
            spin_lock(&i8253_lock);
            outb_p(chip->val61, 0x61);
            outb_p(timer_cnt, 0x42);
            outb(chip->val61 ^ 1, 0x61);
            spin_unlock(&i8253_lock);
      }

      period_bytes = snd_pcm_lib_period_bytes(substream);
      buffer_bytes = snd_pcm_lib_buffer_bytes(substream);
      chip->playback_ptr += PCSP_INDEX_INC() * fmt_size;
      periods_elapsed = chip->playback_ptr - chip->period_ptr;
      if (periods_elapsed < 0) {
            printk(KERN_WARNING "PCSP: playback_ptr inconsistent (%zi %zi %zi)\n",
                  chip->playback_ptr, period_bytes, buffer_bytes);
            periods_elapsed += buffer_bytes;
      }
      periods_elapsed /= period_bytes;
      /* wrap the pointer _before_ calling snd_pcm_period_elapsed(),
       * or ALSA will BUG on us. */
      chip->playback_ptr %= buffer_bytes;

      snd_pcm_stream_unlock(substream);

      if (periods_elapsed) {
            snd_pcm_period_elapsed(substream);
            chip->period_ptr += periods_elapsed * period_bytes;
            chip->period_ptr %= buffer_bytes;
      }

      spin_unlock_irqrestore(&chip->substream_lock, flags);

      if (!chip->timer_active)
            return HRTIMER_NORESTART;
      hrtimer_forward(&chip->timer, chip->timer.expires,
                  ktime_set(0, PCSP_PERIOD_NS()));
      return HRTIMER_RESTART;

exit_nr_unlock2:
      snd_pcm_stream_unlock(substream);
exit_nr_unlock1:
      spin_unlock_irqrestore(&chip->substream_lock, flags);
      return HRTIMER_NORESTART;
}

static void pcsp_start_playing(struct snd_pcsp *chip)
{
      if (chip->timer_active) {
            printk(KERN_ERR "PCSP: Timer already active\n");
            return;
      }

      spin_lock(&i8253_lock);
      chip->val61 = inb(0x61) | 0x03;
      outb_p(0x92, 0x43);     /* binary, mode 1, LSB only, ch 2 */
      spin_unlock(&i8253_lock);
      chip->timer_active = 1;

      tasklet_schedule(&pcsp_start_timer_tasklet);
}

static void pcsp_stop_playing(struct snd_pcsp *chip)
{
      if (!chip->timer_active)
            return;

      chip->timer_active = 0;
      spin_lock(&i8253_lock);
      /* restore the timer */
      outb_p(0xb6, 0x43);     /* binary, mode 3, LSB/MSB, ch 2 */
      outb(chip->val61 & 0xFC, 0x61);
      spin_unlock(&i8253_lock);
}

static int snd_pcsp_playback_close(struct snd_pcm_substream *substream)
{
      struct snd_pcsp *chip = snd_pcm_substream_chip(substream);
#if PCSP_DEBUG
      printk("close called\n");
#endif
      if (chip->timer_active) {
            printk(KERN_ERR "PCSP: timer still active\n");
            pcsp_stop_playing(chip);
      }
      spin_lock_irq(&chip->substream_lock);
      chip->playback_substream = NULL;
      spin_unlock_irq(&chip->substream_lock);
      return 0;
}

static int snd_pcsp_playback_hw_params(struct snd_pcm_substream *substream,
                               struct snd_pcm_hw_params *hw_params)
{
      int err;
      err = snd_pcm_lib_malloc_pages(substream,
                              params_buffer_bytes(hw_params));
      if (err < 0)
            return err;
      return 0;
}

static int snd_pcsp_playback_hw_free(struct snd_pcm_substream *substream)
{
#if PCSP_DEBUG
      printk("hw_free called\n");
#endif
      return snd_pcm_lib_free_pages(substream);
}

static int snd_pcsp_playback_prepare(struct snd_pcm_substream *substream)
{
      struct snd_pcsp *chip = snd_pcm_substream_chip(substream);
#if PCSP_DEBUG
      printk("prepare called, size=%i psize=%i f=%i f1=%i\n",
             snd_pcm_lib_buffer_bytes(substream),
             snd_pcm_lib_period_bytes(substream),
             snd_pcm_lib_buffer_bytes(substream) /
             snd_pcm_lib_period_bytes(substream),
             substream->runtime->periods);
#endif
      chip->playback_ptr = 0;
      chip->period_ptr = 0;
      return 0;
}

static int snd_pcsp_trigger(struct snd_pcm_substream *substream, int cmd)
{
      struct snd_pcsp *chip = snd_pcm_substream_chip(substream);
#if PCSP_DEBUG
      printk("trigger called\n");
#endif
      switch (cmd) {
      case SNDRV_PCM_TRIGGER_START:
      case SNDRV_PCM_TRIGGER_RESUME:
            pcsp_start_playing(chip);
            break;
      case SNDRV_PCM_TRIGGER_STOP:
      case SNDRV_PCM_TRIGGER_SUSPEND:
            pcsp_stop_playing(chip);
            break;
      default:
            return -EINVAL;
      }
      return 0;
}

static snd_pcm_uframes_t snd_pcsp_playback_pointer(struct snd_pcm_substream
                                       *substream)
{
      struct snd_pcsp *chip = snd_pcm_substream_chip(substream);
      return bytes_to_frames(substream->runtime, chip->playback_ptr);
}

static struct snd_pcm_hardware snd_pcsp_playback = {
      .info = (SNDRV_PCM_INFO_INTERLEAVED |
             SNDRV_PCM_INFO_HALF_DUPLEX |
             SNDRV_PCM_INFO_MMAP | SNDRV_PCM_INFO_MMAP_VALID),
      .formats = (SNDRV_PCM_FMTBIT_U8
#if DMIX_WANTS_S16
                | SNDRV_PCM_FMTBIT_S16_LE
#endif
          ),
      .rates = SNDRV_PCM_RATE_KNOT,
      .rate_min = PCSP_DEFAULT_SRATE,
      .rate_max = PCSP_DEFAULT_SRATE,
      .channels_min = 1,
      .channels_max = 1,
      .buffer_bytes_max = PCSP_BUFFER_SIZE,
      .period_bytes_min = 64,
      .period_bytes_max = PCSP_MAX_PERIOD_SIZE,
      .periods_min = 2,
      .periods_max = PCSP_MAX_PERIODS,
      .fifo_size = 0,
};

static int snd_pcsp_playback_open(struct snd_pcm_substream *substream)
{
      struct snd_pcsp *chip = snd_pcm_substream_chip(substream);
      struct snd_pcm_runtime *runtime = substream->runtime;
#if PCSP_DEBUG
      printk("open called\n");
#endif
      if (chip->timer_active) {
            printk(KERN_ERR "PCSP: still active!!\n");
            return -EBUSY;
      }
      runtime->hw = snd_pcsp_playback;
      chip->playback_substream = substream;
      return 0;
}

static struct snd_pcm_ops snd_pcsp_playback_ops = {
      .open = snd_pcsp_playback_open,
      .close = snd_pcsp_playback_close,
      .ioctl = snd_pcm_lib_ioctl,
      .hw_params = snd_pcsp_playback_hw_params,
      .hw_free = snd_pcsp_playback_hw_free,
      .prepare = snd_pcsp_playback_prepare,
      .trigger = snd_pcsp_trigger,
      .pointer = snd_pcsp_playback_pointer,
};

int __init snd_pcsp_new_pcm(struct snd_pcsp *chip)
{
      struct snd_pcm *pcm;
      int err;

      err = snd_pcm_new(chip->card, "pcspeaker", 0, 1, 0, &pcm);
      if (err < 0)
            return err;

      snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, &snd_pcsp_playback_ops);

      pcm->private_data = chip;
      pcm->info_flags = SNDRV_PCM_INFO_HALF_DUPLEX;
      strcpy(pcm->name, "pcsp");

      snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_CONTINUOUS,
                                    snd_dma_continuous_data
                                    (GFP_KERNEL), PCSP_BUFFER_SIZE,
                                    PCSP_BUFFER_SIZE);

      return 0;
}

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