ASoC: Support leaving paths enabled over system suspend

Some devices can usefully run audio while the Linux system is suspended.
One of the most common examples is smartphone systems, which are normally
designed to allow audio to be run between the baseband and the CODEC
without passing through the CPU and so can suspend the CPU when on a
voice call for additional power savings.

Support such systems by providing an API snd_soc_dapm_ignore_suspend().
This can be used to mark DAPM endpoints as not being sensitive to
system suspend. When the system is being suspended paths between
endpoints which are marked as ignoring suspend will be kept active.
Both source and sink must be marked, and there must already be an
active path between the two endpoints prior to suspend.

When paths are active over suspend the bias management will hold the
device bias in the ON state. This is used to avoid suspending the
CODEC while it is still in use.

Tested-by: Peter Ujfalusi <peter.ujfalusi@nokia.com>
Acked-by: Liam Girdwood <lrg@slimlogic.co.uk>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>

1 files changed, 28 insertions, 4 deletions

diff --git a/sound/soc/soc-core.c b/sound/soc/soc-core.c
index 95739767ec45..8661e5b4adb1 100644
--- a/sound/soc/soc-core.c
+++ b/sound/soc/soc-core.c
@@ -927,8 +927,19 @@ static int soc_suspend(struct device *dev)
                                 SND_SOC_DAPM_STREAM_SUSPEND);
         }
 
-        if (codec_dev->suspend)
-                codec_dev->suspend(pdev, PMSG_SUSPEND);
+        /* If there are paths active then the CODEC will be held with
+         * bias _ON and should not be suspended. */
+        if (codec_dev->suspend) {
+                switch (codec->bias_level) {
+                case SND_SOC_BIAS_STANDBY:
+                case SND_SOC_BIAS_OFF:
+                        codec_dev->suspend(pdev, PMSG_SUSPEND);
+                        break;
+                default:
+                        dev_dbg(socdev->dev, "CODEC is on over suspend\n");
+                        break;
+                }
+        }
 
         for (i = 0; i < card->num_links; i++) {
                 struct snd_soc_dai *cpu_dai = card->dai_link[i].cpu_dai;
@@ -975,8 +986,21 @@ static void soc_resume_deferred(struct work_struct *work)
                         cpu_dai->resume(cpu_dai);
         }
 
-        if (codec_dev->resume)
-                codec_dev->resume(pdev);
+        /* If the CODEC was idle over suspend then it will have been
+         * left with bias OFF or STANDBY and suspended so we must now
+         * resume.  Otherwise the suspend was suppressed.
+         */
+        if (codec_dev->resume) {
+                switch (codec->bias_level) {
+                case SND_SOC_BIAS_STANDBY:
+                case SND_SOC_BIAS_OFF:
+                        codec_dev->resume(pdev);
+                        break;
+                default:
+                        dev_dbg(socdev->dev, "CODEC was on over suspend\n");
+                        break;
+                }
+        }
 
         for (i = 0; i < codec->num_dai; i++) {
                 char *stream = codec->dai[i].playback.stream_name;