[patch 20/25] ALSA: hda - Fix DMA position inaccuracy

Greg KH
2008-08-04T21:41:39Z

[-- Attachment #1: alsa-hda-fix-dma-position-inaccuracy.patch --]
[-- Type: text/plain, Size: 7270 bytes --]

2.6.26-stable review patch. If anyone has any objections, please let us
know.

------------------

From: Takashi Iwai <tiwai@suse.de>

commit 9ad593f6d326e7a4664e3856520f6c042f82a37f upstream

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
sound/pci/hda/hda_intel.c | 124 +++++++++++++++++++++++++++++++++++++++-------
1 file changed, 106 insertions(+), 18 deletions(-)

--- 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 *chi
}

+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
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_
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_pc
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
}
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 *p
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 s
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);

--