ASoC: SOF: pm: save io region state in case of errors in resume

If there are failures in DSP runtime resume, the device state will not
reach active and this makes it impossible e.g. to retrieve a possible
DSP panic dump via "exception" debugfs node. If
CONFIG_SND_SOC_SOF_DEBUG_ENABLE_DEBUGFS_CACHE=y is set, the data in
cache is stale. If debugfs cache is not used, the region simply cannot
be read.

To allow debugging these scenarios, update the debugfs cache contents in
resume error handler. User-space can then later retrieve DSP panic and
other state via debugfs (requires SOF debugfs cache to be enabled in
build).

Reported-by: Curtis Malainey <cujomalainey@chromium.org
Link: https://github.com/thesofproject/linux/issues/4274
Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com
Reviewed-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com
Reviewed-by: Curtis Malainey <cujomalainey@chromium.org
Reviewed-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com
Link: https://lore.kernel.org/r/20230512104638.21376-1-peter.ujfalusi@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org

sound/soc/sof/pm.c

@@ -164,7 +164,7 @@ static int sof_resume(struct device *dev, bool runtime_resume)
 		ret = tplg_ops->set_up_all_pipelines(sdev, false);
 		if (ret < 0) {
 			dev_err(sdev->dev, "Failed to restore pipeline after resume %d\n", ret);
-			return ret;
+			goto setup_fail;
 		}
 	}
 
@@ -178,6 +178,18 @@ static int sof_resume(struct device *dev, bool runtime_resume)
 			dev_err(sdev->dev, "ctx_restore IPC error during resume: %d\n", ret);
 	}
 
+setup_fail:
+#if IS_ENABLED(CONFIG_SND_SOC_SOF_DEBUG_ENABLE_DEBUGFS_CACHE)
+	if (ret < 0) {
+		/*
+		 * Debugfs cannot be read in runtime suspend, so cache
+		 * the contents upon failure. This allows to capture
+		 * possible DSP coredump information.
+		 */
+		sof_cache_debugfs(sdev);
+	}
+#endif
+
 	return ret;
 }