Revert: "dma-trace: allocate trace buffer only after enabling traces"

A logical, not "real" git revert of commit eca2089 ("dma-trace:
allocate trace buffer only after enabling traces")

Move dma_trace_buffer_init() away from dma_trace_enable() and back to
dma_trace_init_early()

Restore the early traces removed by that commit. There was no rationale in
the commit message and it was merged without review in PR #255.

Earlier refactorings tried hard to trace early:

- commit 36e425e ("dma-trace: move to earlier initialisation point")
- commit 2b86cb3 ("trace: dma: Make sure we can trace platform
  device initialisation.")

... so it's really not clear why early tracing was removed later. "Rage
quit" to avoid unidentified bugs?

This could have been to save one or two 4k HOST_PAGE_SIZE when the
kernel does not enable DMA traces but I can't see what real-world use
case would leverage such savings _at run-time_; what happens then when
the user changes her mind? We don't have any validation for a use case
so dynamic.

Tracing can be disabled at _compile-time_, recently fixed by
commit 571cc29 ("xtensa/cmake: fix !CONFIG_TRACE")

Signed-off-by: Marc Herbert <marc.herbert@intel.com>

Author: marc-hb

src/trace/dma-trace.c

@@ -46,6 +46,9 @@ static int dma_trace_get_avail_data(struct dma_trace_data *d,
 				    struct dma_trace_buf *buffer,
 				    int avail);
 
+static int  dma_trace_buffer_init(struct dma_trace_data *d);
+static void dma_trace_buffer_free(struct dma_trace_data *d);
+
 /** Periodically runs and starts the DMA even when the buffer is not
  * full.
  */
@@ -141,6 +144,10 @@ int dma_trace_init_early(struct sof *sof)
 
 	sof->dmat = rzalloc(SOF_MEM_ZONE_SYS_SHARED, 0, SOF_MEM_CAPS_RAM, sizeof(*sof->dmat));
 
+	ret = dma_trace_buffer_init(sof->dmat);
+	if (ret)
+		goto err;
+
 	dma_sg_init(&sof->dmat->config.elem_array);
 	k_spinlock_init(&sof->dmat->lock);
 
@@ -152,12 +159,42 @@ int dma_trace_init_early(struct sof *sof)
 		goto err;
 	}
 
+#ifdef __ZEPHYR__
+#define ZEPHYR_VER_OPT " zephyr:" META_QUOTE(BUILD_VERSION)
+#else
+#define ZEPHYR_VER_OPT
+#endif
+
+	/* META_QUOTE(SOF_SRC_HASH) is part of the format string so it
+	 * goes to the .ldc file and does not go to the firmware
+	 * binary. It will be different from SOF_SRC_HASH in case of
+	 * mismatch.
+	 */
+#define SOF_BANNER_COMMON  \
+	"FW ABI 0x%x DBG ABI 0x%x tags SOF:" SOF_GIT_TAG  ZEPHYR_VER_OPT  \
+	" src hash 0x%08x (ldc hash " META_QUOTE(SOF_SRC_HASH) ")"  \
+		" HACK: hardcoded DMA_ATTR_BUFFER_ADDRESS_ALIGNMENT"
+
+
+	/* It should be the very first sent log for easy identification. */
+	mtrace_printf(LOG_LEVEL_INFO,
+		      "SHM: " SOF_BANNER_COMMON,
+		      SOF_ABI_VERSION, SOF_ABI_DBG_VERSION, SOF_SRC_HASH);
+
+	/* Use a different, DMA: prefix to ease identification of log files */
+	tr_info(&dt_tr,
+		"DMA: " SOF_BANNER_COMMON,
+		SOF_ABI_VERSION, SOF_ABI_DBG_VERSION, SOF_SRC_HASH);
+
 	return 0;
 
 err:
 	mtrace_printf(LOG_LEVEL_ERROR,
 		      "dma_trace_init_early() failed: %d", ret);
 
+	if (sof->dmat && sof->dmat->dmatb.addr)
+		dma_trace_buffer_free(sof->dmat);
+
 	/* Cannot rfree(sof->dmat) from the system memory pool, see
 	 * comments in lib/alloc.c
 	 */
@@ -173,9 +210,10 @@ int dma_trace_init_complete(struct dma_trace_data *d)
 
 	tr_info(&dt_tr, "dma_trace_init_complete()");
 
-	if (!d) {
+	if (!dma_trace_initialized(d)) {
 		mtrace_printf(LOG_LEVEL_ERROR,
-			      "dma_trace_init_complete(): failed, no dma_trace_data");
+			      "dma_trace_init_complete(): failed, dmat=%p, dmat->dmatb.addr=%p",
+			      d, d ? d->dmatb.addr : NULL);
 		return -ENOMEM;
 	}
 
@@ -224,6 +262,8 @@ static int dma_trace_buffer_init(struct dma_trace_data *d)
 	void *buf;
 	k_spinlock_key_t key;
 	uint32_t addr_align;
+
+#if 0 // early DMA trace init HACK
 	int err;
 
 	if (!d || !d->dc.dmac) {
@@ -236,6 +276,9 @@ static int dma_trace_buffer_init(struct dma_trace_data *d)
 				&addr_align);
 	if (err < 0)
 		return err;
+#else
+	addr_align = 0x80;
+#endif
 
 	/* For DMA to work properly the buffer must be correctly aligned */
 	buf = rballoc_align(0, SOF_MEM_CAPS_RAM | SOF_MEM_CAPS_DMA,
@@ -418,41 +461,14 @@ static int dma_trace_get_avail_data(struct dma_trace_data *d,
  */
 int dma_trace_enable(struct dma_trace_data *d)
 {
-	int err;
-
-	/* initialize dma trace buffer */
-	err = dma_trace_buffer_init(d);
+	int err = 0;
 
-	if (err < 0) {
-		mtrace_printf(LOG_LEVEL_ERROR, "dma_trace_enable: buffer_init failed");
+	if (!dma_trace_initialized(d)) {
+		mtrace_printf(LOG_LEVEL_ERROR, "No buffer, did dma_init fail?");
+		err = -ENOMEM;
 		goto out;
 	}
 
-#ifdef __ZEPHYR__
-#define ZEPHYR_VER_OPT " zephyr:" META_QUOTE(BUILD_VERSION)
-#else
-#define ZEPHYR_VER_OPT
-#endif
-
-	/* META_QUOTE(SOF_SRC_HASH) is part of the format string so it
-	 * goes to the .ldc file and does not go to the firmware
-	 * binary. It will be different from SOF_SRC_HASH in case of
-	 * mismatch.
-	 */
-#define SOF_BANNER_COMMON  \
-	"FW ABI 0x%x DBG ABI 0x%x tags SOF:" SOF_GIT_TAG  ZEPHYR_VER_OPT  \
-	" src hash 0x%08x (ldc hash " META_QUOTE(SOF_SRC_HASH) ")"
-
-	/* It should be the very first sent log for easy identification. */
-	mtrace_printf(LOG_LEVEL_INFO,
-		      "SHM: " SOF_BANNER_COMMON,
-		      SOF_ABI_VERSION, SOF_ABI_DBG_VERSION, SOF_SRC_HASH);
-
-	/* Use a different, DMA: prefix to ease identification of log files */
-	tr_info(&dt_tr,
-		"DMA: " SOF_BANNER_COMMON,
-		SOF_ABI_VERSION, SOF_ABI_DBG_VERSION, SOF_SRC_HASH);
-
 #if CONFIG_DMA_GW
 	/*
 	 * GW DMA need finish DMA config and start before