linux/include/sound/soc-dpcm.h
Takashi Iwai ea9d0d771f ASoC: dpcm: Fix race between FE/BE updates and trigger
DPCM can update the FE/BE connection states totally asynchronously
from the FE's PCM state.  Most of FE/BE state changes are protected by
mutex, so that they won't race, but there are still some actions that
are uncovered.  For example, suppose to switch a BE while a FE's
stream is running.  This would call soc_dpcm_runtime_update(), which
sets FE's runtime_update flag, then sets up and starts BEs, and clears
FE's runtime_update flag again.

When a device emits XRUN during this operation, the PCM core triggers
snd_pcm_stop(XRUN).  Since the trigger action is an atomic ops, this
isn't blocked by the mutex, thus it kicks off DPCM's trigger action.
It eventually updates and clears FE's runtime_update flag while
soc_dpcm_runtime_update() is running concurrently, and it results in
confusion.

Usually, for avoiding such a race, we take a lock.  There is a PCM
stream lock for that purpose.  However, as already mentioned, the
trigger action is atomic, and we can't take the lock for the whole
soc_dpcm_runtime_update() or other operations that include the lengthy
jobs like hw_params or prepare.

This patch provides an alternative solution.  This adds a way to defer
the conflicting trigger callback to be executed at the end of FE/BE
state changes.  For doing it, two things are introduced:

- Each runtime_update state change of FEs is protected via PCM stream
  lock.
- The FE's trigger callback checks the runtime_update flag.  If it's
  not set, the trigger action is executed there.  If set, mark the
  pending trigger action and returns immediately.
- At the exit of runtime_update state change, it checks whether the
  pending trigger is present.  If yes, it executes the trigger action
  at this point.

Reported-and-tested-by: Qiao Zhou <zhouqiao@marvell.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Acked-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org
2014-11-04 17:18:32 +00:00

163 lines
4.7 KiB
C

/*
* linux/sound/soc-dpcm.h -- ALSA SoC Dynamic PCM Support
*
* Author: Liam Girdwood <lrg@ti.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#ifndef __LINUX_SND_SOC_DPCM_H
#define __LINUX_SND_SOC_DPCM_H
#include <linux/slab.h>
#include <linux/list.h>
#include <sound/pcm.h>
struct snd_soc_pcm_runtime;
/*
* Types of runtime_update to perform. e.g. originated from FE PCM ops
* or audio route changes triggered by muxes/mixers.
*/
enum snd_soc_dpcm_update {
SND_SOC_DPCM_UPDATE_NO = 0,
SND_SOC_DPCM_UPDATE_BE,
SND_SOC_DPCM_UPDATE_FE,
};
/*
* Dynamic PCM Frontend -> Backend link management states.
*/
enum snd_soc_dpcm_link_state {
SND_SOC_DPCM_LINK_STATE_NEW = 0, /* newly created link */
SND_SOC_DPCM_LINK_STATE_FREE, /* link to be dismantled */
};
/*
* Dynamic PCM Frontend -> Backend link PCM states.
*/
enum snd_soc_dpcm_state {
SND_SOC_DPCM_STATE_NEW = 0,
SND_SOC_DPCM_STATE_OPEN,
SND_SOC_DPCM_STATE_HW_PARAMS,
SND_SOC_DPCM_STATE_PREPARE,
SND_SOC_DPCM_STATE_START,
SND_SOC_DPCM_STATE_STOP,
SND_SOC_DPCM_STATE_PAUSED,
SND_SOC_DPCM_STATE_SUSPEND,
SND_SOC_DPCM_STATE_HW_FREE,
SND_SOC_DPCM_STATE_CLOSE,
};
/*
* Dynamic PCM trigger ordering. Triggering flexibility is required as some
* DSPs require triggering before/after their CPU platform and DAIs.
*
* i.e. some clients may want to manually order this call in their PCM
* trigger() whilst others will just use the regular core ordering.
*/
enum snd_soc_dpcm_trigger {
SND_SOC_DPCM_TRIGGER_PRE = 0,
SND_SOC_DPCM_TRIGGER_POST,
SND_SOC_DPCM_TRIGGER_BESPOKE,
};
/*
* Dynamic PCM link
* This links together a FE and BE DAI at runtime and stores the link
* state information and the hw_params configuration.
*/
struct snd_soc_dpcm {
/* FE and BE DAIs*/
struct snd_soc_pcm_runtime *be;
struct snd_soc_pcm_runtime *fe;
/* link state */
enum snd_soc_dpcm_link_state state;
/* list of BE and FE for this DPCM link */
struct list_head list_be;
struct list_head list_fe;
/* hw params for this link - may be different for each link */
struct snd_pcm_hw_params hw_params;
#ifdef CONFIG_DEBUG_FS
struct dentry *debugfs_state;
#endif
};
/*
* Dynamic PCM runtime data.
*/
struct snd_soc_dpcm_runtime {
struct list_head be_clients;
struct list_head fe_clients;
int users;
struct snd_pcm_runtime *runtime;
struct snd_pcm_hw_params hw_params;
/* state and update */
enum snd_soc_dpcm_update runtime_update;
enum snd_soc_dpcm_state state;
int trigger_pending; /* trigger cmd + 1 if pending, 0 if not */
};
/* can this BE stop and free */
int snd_soc_dpcm_can_be_free_stop(struct snd_soc_pcm_runtime *fe,
struct snd_soc_pcm_runtime *be, int stream);
/* can this BE perform a hw_params() */
int snd_soc_dpcm_can_be_params(struct snd_soc_pcm_runtime *fe,
struct snd_soc_pcm_runtime *be, int stream);
/* is the current PCM operation for this FE ? */
int snd_soc_dpcm_fe_can_update(struct snd_soc_pcm_runtime *fe, int stream);
/* is the current PCM operation for this BE ? */
int snd_soc_dpcm_be_can_update(struct snd_soc_pcm_runtime *fe,
struct snd_soc_pcm_runtime *be, int stream);
/* get the substream for this BE */
struct snd_pcm_substream *
snd_soc_dpcm_get_substream(struct snd_soc_pcm_runtime *be, int stream);
/* get the BE runtime state */
enum snd_soc_dpcm_state
snd_soc_dpcm_be_get_state(struct snd_soc_pcm_runtime *be, int stream);
/* set the BE runtime state */
void snd_soc_dpcm_be_set_state(struct snd_soc_pcm_runtime *be, int stream,
enum snd_soc_dpcm_state state);
/* internal use only */
int soc_dpcm_be_digital_mute(struct snd_soc_pcm_runtime *fe, int mute);
int soc_dpcm_debugfs_add(struct snd_soc_pcm_runtime *rtd);
int soc_dpcm_runtime_update(struct snd_soc_card *);
int dpcm_path_get(struct snd_soc_pcm_runtime *fe,
int stream, struct snd_soc_dapm_widget_list **list_);
int dpcm_process_paths(struct snd_soc_pcm_runtime *fe,
int stream, struct snd_soc_dapm_widget_list **list, int new);
int dpcm_be_dai_startup(struct snd_soc_pcm_runtime *fe, int stream);
int dpcm_be_dai_shutdown(struct snd_soc_pcm_runtime *fe, int stream);
void dpcm_be_disconnect(struct snd_soc_pcm_runtime *fe, int stream);
void dpcm_clear_pending_state(struct snd_soc_pcm_runtime *fe, int stream);
int dpcm_be_dai_hw_free(struct snd_soc_pcm_runtime *fe, int stream);
int dpcm_be_dai_hw_params(struct snd_soc_pcm_runtime *fe, int tream);
int dpcm_be_dai_trigger(struct snd_soc_pcm_runtime *fe, int stream, int cmd);
int dpcm_be_dai_prepare(struct snd_soc_pcm_runtime *fe, int stream);
int dpcm_dapm_stream_event(struct snd_soc_pcm_runtime *fe, int dir,
int event);
static inline void dpcm_path_put(struct snd_soc_dapm_widget_list **list)
{
kfree(*list);
}
#endif