ALSA: ASoC: Don't block system resume

On OpenMoko soc-audio resume is taking 700ms of the whole resume time of
1.3s, dominated by writes to the codec over I2C.  This patch shunts the
resume guts into a workqueue which then is done asynchronously.

The "card" is locked using the ALSA power state APIs as suggested by
Mark Brown.

[Added fix for race with resume to suspend and fixed a couple of nits
from checkpatch -- broonie.]

Signed-off-by: Andy Green <andy@openmoko.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

2 files changed, 44 insertions, 3 deletions

diff --git a/include/sound/soc.h b/include/sound/soc.h
index 1f5c62181002..340223a8f24c 100644
--- a/include/sound/soc.h
+++ b/include/sound/soc.h
@@ -510,6 +510,7 @@ struct snd_soc_device {
         struct snd_soc_codec *codec;
         struct snd_soc_codec_device *codec_dev;
         struct delayed_work delayed_work;
+        struct work_struct deferred_resume_work;
         void *codec_data;
 };
 
diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
index c96a6184d66e..b931039632c5 100644
--- a/sound/soc/soc-core.c
+++ b/sound/soc/soc-core.c
@@ -639,6 +639,16 @@ static int soc_suspend(struct platform_device *pdev, pm_message_t state)
         struct snd_soc_codec *codec = socdev->codec;
         int i;
 
+        /* Due to the resume being scheduled into a workqueue we could
+        * suspend before that's finished - wait for it to complete.
+         */
+        snd_power_lock(codec->card);
+        snd_power_wait(codec->card, SNDRV_CTL_POWER_D0);
+        snd_power_unlock(codec->card);
+
+        /* we're going to block userspace touching us until resume completes */
+        snd_power_change_state(codec->card, SNDRV_CTL_POWER_D3hot);
+
         /* mute any active DAC's */
         for (i = 0; i < machine->num_links; i++) {
                 struct snd_soc_codec_dai *dai = machine->dai_link[i].codec_dai;
@@ -691,16 +701,27 @@ static int soc_suspend(struct platform_device *pdev, pm_message_t state)
         return 0;
 }
 
-/* powers up audio subsystem after a suspend */
-static int soc_resume(struct platform_device *pdev)
+/* deferred resume work, so resume can complete before we finished
+ * setting our codec back up, which can be very slow on I2C
+ */
+static void soc_resume_deferred(struct work_struct *work)
 {
-        struct snd_soc_device *socdev = platform_get_drvdata(pdev);
+        struct snd_soc_device *socdev = container_of(work,
+                                                     struct snd_soc_device,
+                                                     deferred_resume_work);
         struct snd_soc_machine *machine = socdev->machine;
         struct snd_soc_platform *platform = socdev->platform;
         struct snd_soc_codec_device *codec_dev = socdev->codec_dev;
         struct snd_soc_codec *codec = socdev->codec;
+        struct platform_device *pdev = to_platform_device(socdev->dev);
         int i;
 
+        /* our power state is still SNDRV_CTL_POWER_D3hot from suspend time,
+         * so userspace apps are blocked from touching us
+         */
+
+        dev_info(socdev->dev, "starting resume work\n");
+
         if (machine->resume_pre)
                 machine->resume_pre(pdev);
 
@@ -742,6 +763,22 @@ static int soc_resume(struct platform_device *pdev)
         if (machine->resume_post)
                 machine->resume_post(pdev);
 
+        dev_info(socdev->dev, "resume work completed\n");
+
+        /* userspace can access us now we are back as we were before */
+        snd_power_change_state(codec->card, SNDRV_CTL_POWER_D0);
+}
+
+/* powers up audio subsystem after a suspend */
+static int soc_resume(struct platform_device *pdev)
+{
+        struct snd_soc_device *socdev = platform_get_drvdata(pdev);
+
+        dev_info(socdev->dev, "scheduling resume work\n");
+
+        if (!schedule_work(&socdev->deferred_resume_work))
+                dev_err(socdev->dev, "work item may be lost\n");
+
         return 0;
 }
 
@@ -788,6 +825,9 @@ static int soc_probe(struct platform_device *pdev)
 
         /* DAPM stream work */
         INIT_DELAYED_WORK(&socdev->delayed_work, close_delayed_work);
+        /* deferred resume work */
+        INIT_WORK(&socdev->deferred_resume_work, soc_resume_deferred);
+
         return 0;
 
 platform_err: