[ALSA] hda - Fix DMA position inaccuracy

Many HD-audio controllers seem inaccurate about the IRQ timing of
PCM period updates.  This has caused problems on audio quality; e.g.
JACK doesn't work with two periods.

This patch fixes the problem by checking the current DMA position
at IRQ handler and delays the period-update via a workq if it's
inaccurate.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

diff --git a/sound/pci/hda/hda_intel.c b/sound/pci/hda/hda_intel.c
index b3a618e..6ba7ac0 100644 (file)
--- a/sound/pci/hda/hda_intel.c
+++ b/sound/pci/hda/hda_intel.c
@@ -285,6 +285,7 @@ struct azx_dev {
        u32 *posbuf;            /* position buffer pointer */
 
        unsigned int bufsize;   /* size of the play buffer in bytes */
+       unsigned int period_bytes; /* size of the period in bytes */
        unsigned int frags;     /* number for period in the play buffer */
        unsigned int fifo_size; /* FIFO size */
 
@@ -301,11 +302,10 @@ struct azx_dev {
                                         */
        unsigned char stream_tag;       /* assigned stream */
        unsigned char index;            /* stream index */
-       /* for sanity check of position buffer */
-       unsigned int period_intr;
 
        unsigned int opened :1;
        unsigned int running :1;
+       unsigned int irq_pending: 1;
 };
 
 /* CORB/RIRB */
@@ -369,6 +369,9 @@ struct azx {
 
        /* for debugging */
        unsigned int last_cmd;  /* last issued command (to sync) */
+
+       /* for pending irqs */
+       struct work_struct irq_pending_work;
 };
 
 /* driver types */
@@ -908,6 +911,8 @@ static void azx_init_pci(struct azx *chip)
 }
 
 
+static int azx_position_ok(struct azx *chip, struct azx_dev *azx_dev);
+
 /*
  * interrupt handler
  */
@@ -930,11 +935,18 @@ static irqreturn_t azx_interrupt(int irq, void *dev_id)
                azx_dev = &chip->azx_dev[i];
                if (status & azx_dev->sd_int_sta_mask) {
                        azx_sd_writeb(azx_dev, SD_STS, SD_INT_MASK);
-                       if (azx_dev->substream && azx_dev->running) {
-                               azx_dev->period_intr++;
+                       if (!azx_dev->substream || !azx_dev->running)
+                               continue;
+                       /* check whether this IRQ is really acceptable */
+                       if (azx_position_ok(chip, azx_dev)) {
+                               azx_dev->irq_pending = 0;
                                spin_unlock(&chip->reg_lock);
                                snd_pcm_period_elapsed(azx_dev->substream);
                                spin_lock(&chip->reg_lock);
+                       } else {
+                               /* bogus IRQ, process it later */
+                               azx_dev->irq_pending = 1;
+                               schedule_work(&chip->irq_pending_work);
                        }
                }
        }
@@ -973,6 +985,7 @@ static int azx_setup_periods(struct snd_pcm_substream *substream,
        azx_sd_writel(azx_dev, SD_BDLPU, 0);
 
        period_bytes = snd_pcm_lib_period_bytes(substream);
+       azx_dev->period_bytes = period_bytes;
        periods = azx_dev->bufsize / period_bytes;
 
        /* program the initial BDL entries */
@@ -1421,27 +1434,16 @@ static int azx_pcm_trigger(struct snd_pcm_substream *substream, int cmd)
        return 0;
 }
 
-static snd_pcm_uframes_t azx_pcm_pointer(struct snd_pcm_substream *substream)
+static unsigned int azx_get_position(struct azx *chip,
+                                    struct azx_dev *azx_dev)
 {
-       struct azx_pcm *apcm = snd_pcm_substream_chip(substream);
-       struct azx *chip = apcm->chip;
-       struct azx_dev *azx_dev = get_azx_dev(substream);
        unsigned int pos;
 
        if (chip->position_fix == POS_FIX_POSBUF ||
            chip->position_fix == POS_FIX_AUTO) {
                /* use the position buffer */
                pos = le32_to_cpu(*azx_dev->posbuf);
-               if (chip->position_fix == POS_FIX_AUTO &&
-                   azx_dev->period_intr == 1 && !pos) {
-                       printk(KERN_WARNING
-                              "hda-intel: Invalid position buffer, "
-                              "using LPIB read method instead.\n");
-                       chip->position_fix = POS_FIX_NONE;
-                       goto read_lpib;
-               }
        } else {
-       read_lpib:
                /* read LPIB */
                pos = azx_sd_readl(azx_dev, SD_LPIB);
                if (chip->position_fix == POS_FIX_FIFO)
@@ -1449,7 +1451,90 @@ static snd_pcm_uframes_t azx_pcm_pointer(struct snd_pcm_substream *substream)
        }
        if (pos >= azx_dev->bufsize)
                pos = 0;
-       return bytes_to_frames(substream->runtime, pos);
+       return pos;
+}
+
+static snd_pcm_uframes_t azx_pcm_pointer(struct snd_pcm_substream *substream)
+{
+       struct azx_pcm *apcm = snd_pcm_substream_chip(substream);
+       struct azx *chip = apcm->chip;
+       struct azx_dev *azx_dev = get_azx_dev(substream);
+       return bytes_to_frames(substream->runtime,
+                              azx_get_position(chip, azx_dev));
+}
+
+/*
+ * Check whether the current DMA position is acceptable for updating
+ * periods.  Returns non-zero if it's OK.
+ *
+ * Many HD-audio controllers appear pretty inaccurate about
+ * the update-IRQ timing.  The IRQ is issued before actually the
+ * data is processed.  So, we need to process it afterwords in a
+ * workqueue.
+ */
+static int azx_position_ok(struct azx *chip, struct azx_dev *azx_dev)
+{
+       unsigned int pos;
+
+       pos = azx_get_position(chip, azx_dev);
+       if (chip->position_fix == POS_FIX_AUTO) {
+               if (!pos) {
+                       printk(KERN_WARNING
+                              "hda-intel: Invalid position buffer, "
+                              "using LPIB read method instead.\n");
+                       chip->position_fix = POS_FIX_NONE;
+                       pos = azx_get_position(chip, azx_dev);
+               } else
+                       chip->position_fix = POS_FIX_POSBUF;
+       }
+
+       if (pos % azx_dev->period_bytes > azx_dev->period_bytes / 2)
+               return 0; /* NG - it's below the period boundary */
+       return 1; /* OK, it's fine */
+}
+
+/*
+ * The work for pending PCM period updates.
+ */
+static void azx_irq_pending_work(struct work_struct *work)
+{
+       struct azx *chip = container_of(work, struct azx, irq_pending_work);
+       int i, pending;
+
+       for (;;) {
+               pending = 0;
+               spin_lock_irq(&chip->reg_lock);
+               for (i = 0; i < chip->num_streams; i++) {
+                       struct azx_dev *azx_dev = &chip->azx_dev[i];
+                       if (!azx_dev->irq_pending ||
+                           !azx_dev->substream ||
+                           !azx_dev->running)
+                               continue;
+                       if (azx_position_ok(chip, azx_dev)) {
+                               azx_dev->irq_pending = 0;
+                               spin_unlock(&chip->reg_lock);
+                               snd_pcm_period_elapsed(azx_dev->substream);
+                               spin_lock(&chip->reg_lock);
+                       } else
+                               pending++;
+               }
+               spin_unlock_irq(&chip->reg_lock);
+               if (!pending)
+                       return;
+               cond_resched();
+       }
+}
+
+/* clear irq_pending flags and assure no on-going workq */
+static void azx_clear_irq_pending(struct azx *chip)
+{
+       int i;
+
+       spin_lock_irq(&chip->reg_lock);
+       for (i = 0; i < chip->num_streams; i++)
+               chip->azx_dev[i].irq_pending = 0;
+       spin_unlock_irq(&chip->reg_lock);
+       flush_scheduled_work();
 }
 
 static struct snd_pcm_ops azx_pcm_ops = {
@@ -1676,6 +1761,7 @@ static int azx_suspend(struct pci_dev *pci, pm_message_t state)
        int i;
 
        snd_power_change_state(card, SNDRV_CTL_POWER_D3hot);
+       azx_clear_irq_pending(chip);
        for (i = 0; i < AZX_MAX_PCMS; i++)
                snd_pcm_suspend_all(chip->pcm[i]);
        if (chip->initialized)
@@ -1732,6 +1818,7 @@ static int azx_free(struct azx *chip)
        int i;
 
        if (chip->initialized) {
+               azx_clear_irq_pending(chip);
                for (i = 0; i < chip->num_streams; i++)
                        azx_stream_stop(chip, &chip->azx_dev[i]);
                azx_stop_chip(chip);
@@ -1857,6 +1944,7 @@ static int __devinit azx_create(struct snd_card *card, struct pci_dev *pci,
        chip->irq = -1;
        chip->driver_type = driver_type;
        chip->msi = enable_msi;
+       INIT_WORK(&chip->irq_pending_work, azx_irq_pending_work);
 
        chip->position_fix = check_position_fix(chip, position_fix[dev]);
        check_probe_mask(chip, dev);