ASoC: SOF: trace: move to opt-in with Kconfig and module parameter

In a number of debug cases, the DMA-based trace can add problems
(e.g. with HDaudio channel allocation). It also generates additional
traffic on the bus and if the DMA handling is unreliable will prevent
audio use-cases from working normally. Using the trace also requires
tools to be installed on the target.

The trace can be instead handled as dynamic debug. We can use a
Kconfig to force the trace to be enabled in all cases, or use a module
parameter to enable it on a need-basis, e.g. by setting "options
snd_sof sof_debug=0x1" in a /etc/modprobe.d file.

Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>

Author: plbossart

sound/soc/sof/Kconfig

@@ -128,6 +128,14 @@ config SND_SOC_SOF_DEBUG_ENABLE_DEBUGFS_CACHE
 	  Say Y if you want to enable caching the memory windows.
 	  If unsure, select "N".
 
+config SND_SOC_SOF_DEBUG_ENABLE_FIRMWARE_TRACE
+	bool "SOF enable firmware trace"
+	help
+	  The firmware trace can be enabled either at build-time with
+	  this option, or dynamically by setting flags in the SOF core
+	  module parameter (similar to dynamic debug)
+	  If unsure, select "N".
+
 endif ## SND_SOC_SOF_DEBUG
 
 endif ## SND_SOC_SOF_OPTIONS

sound/soc/sof/core.c

@@ -16,6 +16,12 @@
 #include "sof-priv.h"
 #include "ops.h"
 
+static int sof_core_debug;
+module_param_named(sof_debug, sof_core_debug, int, 0444);
+MODULE_PARM_DESC(sof_debug, "SOF core debug options (0x0 all off)");
+
+#define SOF_CORE_ENABLE_TRACE BIT(0)
+
 /* SOF defaults if not provided by the platform in ms */
 #define TIMEOUT_DEFAULT_IPC_MS  5
 #define TIMEOUT_DEFAULT_BOOT_MS 100
@@ -350,12 +356,20 @@ static int sof_probe_continue(struct snd_sof_dev *sdev)
 		goto fw_run_err;
 	}
 
-	/* init DMA trace */
-	ret = snd_sof_init_trace(sdev);
-	if (ret < 0) {
-		/* non fatal */
-		dev_warn(sdev->dev,
-			 "warning: failed to initialize trace %d\n", ret);
+	if (IS_ENABLED(CONFIG_SND_SOC_SOF_DEBUG_ENABLE_FIRMWARE_TRACE) ||
+	    (sof_core_debug & SOF_CORE_ENABLE_TRACE)) {
+		sdev->dtrace_is_supported = true;
+
+		/* init DMA trace */
+		ret = snd_sof_init_trace(sdev);
+		if (ret < 0) {
+			/* non fatal */
+			dev_warn(sdev->dev,
+				 "warning: failed to initialize trace %d\n",
+				 ret);
+		}
+	} else {
+		dev_dbg(sdev->dev, "SOF firmware trace disabled\n");
 	}
 
 	/* hereafter all FW boot flows are for PM reasons */

sound/soc/sof/sof-priv.h

@@ -415,6 +415,7 @@ struct snd_sof_dev {
 	int dma_trace_pages;
 	wait_queue_head_t trace_sleep;
 	u32 host_offset;
+	u32 dtrace_is_supported; /* set with Kconfig or module parameter */
 	u32 dtrace_is_enabled;
 	u32 dtrace_error;
 	u32 dtrace_draining;

sound/soc/sof/trace.c

@@ -167,6 +167,9 @@ int snd_sof_init_trace_ipc(struct snd_sof_dev *sdev)
 	struct sof_ipc_reply ipc_reply;
 	int ret;
 
+	if (!sdev->dtrace_is_supported)
+		return 0;
+
 	if (sdev->dtrace_is_enabled || !sdev->dma_trace_pages)
 		return -EINVAL;
 
@@ -227,6 +230,9 @@ int snd_sof_init_trace(struct snd_sof_dev *sdev)
 {
 	int ret;
 
+	if (!sdev->dtrace_is_supported)
+		return 0;
+
 	/* set false before start initialization */
 	sdev->dtrace_is_enabled = false;
 
@@ -282,6 +288,9 @@ EXPORT_SYMBOL(snd_sof_init_trace);
 int snd_sof_trace_update_pos(struct snd_sof_dev *sdev,
 			     struct sof_ipc_dma_trace_posn *posn)
 {
+	if (!sdev->dtrace_is_supported)
+		return 0;
+
 	if (sdev->dtrace_is_enabled && sdev->host_offset != posn->host_offset) {
 		sdev->host_offset = posn->host_offset;
 		wake_up(&sdev->trace_sleep);
@@ -298,6 +307,9 @@ int snd_sof_trace_update_pos(struct snd_sof_dev *sdev,
 /* an error has occurred within the DSP that prevents further trace */
 void snd_sof_trace_notify_for_error(struct snd_sof_dev *sdev)
 {
+	if (!sdev->dtrace_is_supported)
+		return;
+
 	if (sdev->dtrace_is_enabled) {
 		dev_err(sdev->dev, "error: waking up any trace sleepers\n");
 		sdev->dtrace_error = true;
@@ -310,7 +322,7 @@ void snd_sof_release_trace(struct snd_sof_dev *sdev)
 {
 	int ret;
 
-	if (!sdev->dtrace_is_enabled)
+	if (!sdev->dtrace_is_supported || !sdev->dtrace_is_enabled)
 		return;
 
 	ret = snd_sof_dma_trace_trigger(sdev, SNDRV_PCM_TRIGGER_STOP);
@@ -331,6 +343,9 @@ EXPORT_SYMBOL(snd_sof_release_trace);
 
 void snd_sof_free_trace(struct snd_sof_dev *sdev)
 {
+	if (!sdev->dtrace_is_supported)
+		return;
+
 	snd_sof_release_trace(sdev);
 
 	snd_dma_free_pages(&sdev->dmatb);