ASoC: SOF: Intel: hda: Allow trace DMA in S0 when DSP is in D0I3 for debug

Trace DMA is disabled by default when the DSP is in D0I3.
Add a debug option to keep trace DMA enabled when the DSP
is in D0I3 during S0.
Signed-off-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Signed-off-by: Keyon Jie <yang.jie@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20200129220726.31792-10-pierre-louis.bossart@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/intel/hda-dsp.c

@@ -15,6 +15,7 @@
  * Hardware interface for generic Intel audio DSP HDA IP
  */
 
+#include <linux/module.h>
 #include <sound/hdaudio_ext.h>
 #include <sound/hda_register.h>
 #include "../sof-audio.h"
@@ -22,6 +23,13 @@
 #include "hda.h"
 #include "hda-ipc.h"
 
+static bool hda_enable_trace_D0I3_S0;
+#if IS_ENABLED(CONFIG_SND_SOC_SOF_DEBUG)
+module_param_named(enable_trace_D0I3_S0, hda_enable_trace_D0I3_S0, bool, 0444);
+MODULE_PARM_DESC(enable_trace_D0I3_S0,
+		 "SOF HDA enable trace when the DSP is in D0I3 in S0");
+#endif
+
 /*
  * DSP Core control.
  */
@@ -399,8 +407,14 @@ static int hda_dsp_set_D0_state(struct snd_sof_dev *sdev,
 	if (target_state->substate == SOF_HDA_DSP_PM_D0I3) {
 		value = SOF_HDA_VS_D0I3C_I3;
 
-		/* disable DMA trace in D0I3 */
-		flags = HDA_PM_NO_DMA_TRACE;
+		/*
+		 * Trace DMA is disabled by default when the DSP enters D0I3.
+		 * But it can be kept enabled when the DSP enters D0I3 while the
+		 * system is in S0 for debug.
+		 */
+		if (hda_enable_trace_D0I3_S0 &&
+		    sdev->system_suspend_target != SOF_SUSPEND_NONE)
+			flags = HDA_PM_NO_DMA_TRACE;
 	} else {
 		/* prevent power gating in D0I0 */
 		flags = HDA_PM_PPG;
@@ -450,11 +464,26 @@ int hda_dsp_set_power_state(struct snd_sof_dev *sdev,
 {
 	int ret = 0;
 
-	/* Nothing to do if the DSP is already in the requested state */
+	/*
+	 * When the DSP is already in D0I3 and the target state is D0I3,
+	 * it could be the case that the DSP is in D0I3 during S0
+	 * and the system is suspending to S0Ix. Therefore,
+	 * hda_dsp_set_D0_state() must be called to disable trace DMA
+	 * by sending the PM_GATE IPC to the FW.
+	 */
+	if (target_state->substate == SOF_HDA_DSP_PM_D0I3 &&
+	    sdev->system_suspend_target == SOF_SUSPEND_S0IX)
+		goto set_state;
+
+	/*
+	 * For all other cases, return without doing anything if
+	 * the DSP is already in the target state.
+	 */
 	if (target_state->state == sdev->dsp_power_state.state &&
 	    target_state->substate == sdev->dsp_power_state.substate)
 		return 0;
 
+set_state:
 	switch (target_state->state) {
 	case SOF_DSP_PM_D0:
 		ret = hda_dsp_set_D0_state(sdev, target_state);