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ALSA: pcm_lib - add possibility to log last 10 DMA ring buffer positions
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In some debug cases, it might be usefull to see previous ring buffer
positions to determine position problems from the lowlevel drivers.

Signed-off-by: Jaroslav Kysela <perex@perex.cz>
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@perexg
perexg committed Jan 7, 2010
1 parent 741b20c commit 4d96eb2
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Showing 3 changed files with 127 additions and 23 deletions.
6 changes: 6 additions & 0 deletions include/sound/pcm.h
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Original file line number Diff line number Diff line change
Expand Up @@ -262,6 +262,8 @@ struct snd_pcm_hw_constraint_list {
unsigned int mask;
};

struct snd_pcm_hwptr_log;

struct snd_pcm_runtime {
/* -- Status -- */
struct snd_pcm_substream *trigger_master;
Expand Down Expand Up @@ -340,6 +342,10 @@ struct snd_pcm_runtime {
/* -- OSS things -- */
struct snd_pcm_oss_runtime oss;
#endif

#ifdef CONFIG_SND_PCM_XRUN_DEBUG
struct snd_pcm_hwptr_log *hwptr_log;
#endif
};

struct snd_pcm_group { /* keep linked substreams */
Expand Down
4 changes: 4 additions & 0 deletions sound/core/pcm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -921,6 +921,10 @@ void snd_pcm_detach_substream(struct snd_pcm_substream *substream)
snd_free_pages((void*)runtime->control,
PAGE_ALIGN(sizeof(struct snd_pcm_mmap_control)));
kfree(runtime->hw_constraints.rules);
#ifdef CONFIG_SND_PCM_XRUN_DEBUG
if (runtime->hwptr_log)
kfree(runtime->hwptr_log);
#endif
kfree(runtime);
substream->runtime = NULL;
put_pid(substream->pid);
Expand Down
140 changes: 117 additions & 23 deletions sound/core/pcm_lib.c
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Original file line number Diff line number Diff line change
Expand Up @@ -126,34 +126,34 @@ void snd_pcm_playback_silence(struct snd_pcm_substream *substream, snd_pcm_ufram
}
}

static void pcm_debug_name(struct snd_pcm_substream *substream,
char *name, size_t len)
{
snprintf(name, len, "pcmC%dD%d%c:%d",
substream->pcm->card->number,
substream->pcm->device,
substream->stream ? 'c' : 'p',
substream->number);
}

#define XRUN_DEBUG_BASIC (1<<0)
#define XRUN_DEBUG_STACK (1<<1) /* dump also stack */
#define XRUN_DEBUG_JIFFIESCHECK (1<<2) /* do jiffies check */
#define XRUN_DEBUG_PERIODUPDATE (1<<3) /* full period update info */
#define XRUN_DEBUG_HWPTRUPDATE (1<<4) /* full hwptr update info */
#define XRUN_DEBUG_LOG (1<<5) /* show last 10 positions on err */
#define XRUN_DEBUG_LOGONCE (1<<6) /* do above only once */

#ifdef CONFIG_SND_PCM_XRUN_DEBUG

#define xrun_debug(substream, mask) \
((substream)->pstr->xrun_debug & (mask))
#else
#define xrun_debug(substream, mask) 0
#endif

#define dump_stack_on_xrun(substream) do { \
if (xrun_debug(substream, XRUN_DEBUG_STACK)) \
dump_stack(); \
} while (0)

static void pcm_debug_name(struct snd_pcm_substream *substream,
char *name, size_t len)
{
snprintf(name, len, "pcmC%dD%d%c:%d",
substream->pcm->card->number,
substream->pcm->device,
substream->stream ? 'c' : 'p',
substream->number);
}

static void xrun(struct snd_pcm_substream *substream)
{
struct snd_pcm_runtime *runtime = substream->runtime;
Expand All @@ -169,6 +169,102 @@ static void xrun(struct snd_pcm_substream *substream)
}
}

#define hw_ptr_error(substream, fmt, args...) \
do { \
if (xrun_debug(substream, XRUN_DEBUG_BASIC)) { \
if (printk_ratelimit()) { \
snd_printd("PCM: " fmt, ##args); \
} \
dump_stack_on_xrun(substream); \
} \
} while (0)

#define XRUN_LOG_CNT 10

struct hwptr_log_entry {
unsigned long jiffies;
snd_pcm_uframes_t pos;
snd_pcm_uframes_t period_size;
snd_pcm_uframes_t buffer_size;
snd_pcm_uframes_t old_hw_ptr;
snd_pcm_uframes_t hw_ptr_base;
snd_pcm_uframes_t hw_ptr_interrupt;
};

struct snd_pcm_hwptr_log {
unsigned int idx;
unsigned int hit: 1;
struct hwptr_log_entry entries[XRUN_LOG_CNT];
};

static void xrun_log(struct snd_pcm_substream *substream,
snd_pcm_uframes_t pos)
{
struct snd_pcm_runtime *runtime = substream->runtime;
struct snd_pcm_hwptr_log *log = runtime->hwptr_log;
struct hwptr_log_entry *entry;

if (log == NULL) {
log = kzalloc(sizeof(*log), GFP_ATOMIC);
if (log == NULL)
return;
runtime->hwptr_log = log;
} else {
if (xrun_debug(substream, XRUN_DEBUG_LOGONCE) && log->hit)
return;
}
entry = &log->entries[log->idx];
entry->jiffies = jiffies;
entry->pos = pos;
entry->period_size = runtime->period_size;
entry->buffer_size = runtime->buffer_size;;
entry->old_hw_ptr = runtime->status->hw_ptr;
entry->hw_ptr_base = runtime->hw_ptr_base;
entry->hw_ptr_interrupt = runtime->hw_ptr_interrupt;;
log->idx = (log->idx + 1) % XRUN_LOG_CNT;
}

static void xrun_log_show(struct snd_pcm_substream *substream)
{
struct snd_pcm_hwptr_log *log = substream->runtime->hwptr_log;
struct hwptr_log_entry *entry;
char name[16];
unsigned int idx;
int cnt;

if (log == NULL)
return;
if (xrun_debug(substream, XRUN_DEBUG_LOGONCE) && log->hit)
return;
pcm_debug_name(substream, name, sizeof(name));
for (cnt = 0, idx = log->idx; cnt < XRUN_LOG_CNT; cnt++) {
entry = &log->entries[idx];
if (entry->period_size == 0)
break;
snd_printd("hwptr log: %s: j=%lu, pos=0x%lx/0x%lx/0x%lx, "
"hwptr=0x%lx, hw_base=0x%lx, hw_intr=0x%lx\n",
name, entry->jiffies, (unsigned long)entry->pos,
(unsigned long)entry->period_size,
(unsigned long)entry->buffer_size,
(unsigned long)entry->old_hw_ptr,
(unsigned long)entry->hw_ptr_base,
(unsigned long)entry->hw_ptr_interrupt);
idx++;
idx %= XRUN_LOG_CNT;
}
log->hit = 1;
}

#else /* ! CONFIG_SND_PCM_XRUN_DEBUG */

#define xrun_debug(substream, mask) 0
#define xrun(substream) do { } while (0)
#define hw_ptr_error(substream, fmt, args...) do { } while (0)
#define xrun_log(substream, pos) do { } while (0)
#define xrun_log_show(substream) do { } while (0)

#endif

static snd_pcm_uframes_t
snd_pcm_update_hw_ptr_pos(struct snd_pcm_substream *substream,
struct snd_pcm_runtime *runtime)
Expand All @@ -182,6 +278,7 @@ snd_pcm_update_hw_ptr_pos(struct snd_pcm_substream *substream,
if (printk_ratelimit()) {
char name[16];
pcm_debug_name(substream, name, sizeof(name));
xrun_log_show(substream);
snd_printd(KERN_ERR "BUG: %s, pos = 0x%lx, "
"buffer size = 0x%lx, period size = 0x%lx\n",
name, pos, runtime->buffer_size,
Expand All @@ -190,6 +287,8 @@ snd_pcm_update_hw_ptr_pos(struct snd_pcm_substream *substream,
pos = 0;
}
pos -= pos % runtime->min_align;
if (xrun_debug(substream, XRUN_DEBUG_LOG))
xrun_log(substream, pos);
return pos;
}

Expand Down Expand Up @@ -220,16 +319,6 @@ static int snd_pcm_update_hw_ptr_post(struct snd_pcm_substream *substream,
return 0;
}

#define hw_ptr_error(substream, fmt, args...) \
do { \
if (xrun_debug(substream, XRUN_DEBUG_BASIC)) { \
if (printk_ratelimit()) { \
snd_printd("PCM: " fmt, ##args); \
} \
dump_stack_on_xrun(substream); \
} \
} while (0)

static int snd_pcm_update_hw_ptr_interrupt(struct snd_pcm_substream *substream)
{
struct snd_pcm_runtime *runtime = substream->runtime;
Expand Down Expand Up @@ -270,6 +359,7 @@ static int snd_pcm_update_hw_ptr_interrupt(struct snd_pcm_substream *substream)
if (runtime->periods == 1 || new_hw_ptr < old_hw_ptr)
delta += runtime->buffer_size;
if (delta < 0) {
xrun_log_show(substream);
hw_ptr_error(substream,
"Unexpected hw_pointer value "
"(stream=%i, pos=%ld, intr_ptr=%ld)\n",
Expand Down Expand Up @@ -315,6 +405,7 @@ static int snd_pcm_update_hw_ptr_interrupt(struct snd_pcm_substream *substream)
delta = jdelta /
(((runtime->period_size * HZ) / runtime->rate)
+ HZ/100);
xrun_log_show(substream);
hw_ptr_error(substream,
"hw_ptr skipping! [Q] "
"(pos=%ld, delta=%ld, period=%ld, "
Expand All @@ -334,6 +425,7 @@ static int snd_pcm_update_hw_ptr_interrupt(struct snd_pcm_substream *substream)
}
no_jiffies_check:
if (delta > runtime->period_size + runtime->period_size / 2) {
xrun_log_show(substream);
hw_ptr_error(substream,
"Lost interrupts? "
"(stream=%i, delta=%ld, intr_ptr=%ld)\n",
Expand Down Expand Up @@ -397,6 +489,7 @@ int snd_pcm_update_hw_ptr(struct snd_pcm_substream *substream)
if (delta < 0) {
delta += runtime->buffer_size;
if (delta < 0) {
xrun_log_show(substream);
hw_ptr_error(substream,
"Unexpected hw_pointer value [2] "
"(stream=%i, pos=%ld, old_ptr=%ld, jdelta=%li)\n",
Expand All @@ -416,6 +509,7 @@ int snd_pcm_update_hw_ptr(struct snd_pcm_substream *substream)
goto no_jiffies_check;
delta -= runtime->delay;
if (((delta * HZ) / runtime->rate) > jdelta + HZ/100) {
xrun_log_show(substream);
hw_ptr_error(substream,
"hw_ptr skipping! "
"(pos=%ld, delta=%ld, period=%ld, jdelta=%lu/%lu)\n",
Expand Down

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