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>
Link: https://lore.kernel.org/r/20190927200538.660-4-pierre-louis.bossart@linux.intel.comSigned-off-by: Mark Brown <broonie@kernel.org>

sound/soc/sof/Kconfig

@@ -142,6 +142,14 @@ 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".
+
 config SND_SOC_SOF_DEBUG_IPC_FLOOD_TEST
 	bool "SOF enable IPC flood test"
 	help

sound/soc/sof/core.c

@@ -16,6 +16,11 @@
 #include "sof-priv.h"
 #include "ops.h"
 
+/* see SOF_DBG_ flags */
+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)");
+
 /* SOF defaults if not provided by the platform in ms */
 #define TIMEOUT_DEFAULT_IPC_MS  500
 #define TIMEOUT_DEFAULT_BOOT_MS 2000
@@ -350,12 +355,20 @@ 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_DBG_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

@@ -28,10 +28,14 @@
 #include <uapi/sound/sof/fw.h>
 
 /* debug flags */
-#define SOF_DBG_REGS	BIT(1)
-#define SOF_DBG_MBOX	BIT(2)
-#define SOF_DBG_TEXT	BIT(3)
-#define SOF_DBG_PCI	BIT(4)
+#define SOF_DBG_ENABLE_TRACE	BIT(0)
+#define SOF_DBG_REGS		BIT(1)
+#define SOF_DBG_MBOX		BIT(2)
+#define SOF_DBG_TEXT		BIT(3)
+#define SOF_DBG_PCI		BIT(4)
+
+/* global debug state set by SOF_DBG_ flags */
+extern int sof_core_debug;
 
 /* max BARs mmaped devices can use */
 #define SND_SOF_BARS	8
@@ -434,6 +438,7 @@ 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

@@ -162,6 +162,9 @@ 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;
 
@@ -222,6 +225,9 @@ 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;
 
@@ -277,6 +283,9 @@ 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);
@@ -293,6 +302,9 @@ 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;
@@ -305,7 +317,7 @@ 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);
@@ -326,6 +338,9 @@ 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);