ASoC: SOF: trace: Use proper DMA direction for the trace data buffer

Buffers allocated with snd_dma_alloc_pages() will have DMA direction
DMA_BIDIRECTIONAL. The trace data memory is only used for one DMA
direction: DMA_FROM_DEVICE, DMA only writes there, never reads.

We also need to do a sync before accessing (reading with CPU) from the
trace data buffer to copy it to user space.

Note: snd_dma_buffer_sync() is also used for normal playback and capture
streams to make sure that the data is available for the DMA or CPU.

Reviewed-by: Ranjani Sridharan <ranjani.sridharan@linux.intel.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20220310171651.249385-4-pierre-louis.bossart@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/sound/soc/sof/trace.c b/sound/soc/sof/trace.c
index 104388c551cb3f23a1ba3ce0e6a6d04426cb027d..ea8e4506d02e6670376c70a4e9298ae52026937f 100644 (file)
--- a/sound/soc/sof/trace.c
+++ b/sound/soc/sof/trace.c
@@ -320,6 +320,13 @@ static ssize_t sof_dfsentry_trace_read(struct file *file, char __user *buffer,
        if (count > avail)
                count = avail;
 
+       /*
+        * make sure that all trace data is available for the CPU as the trace
+        * data buffer might be allocated from non consistent memory.
+        * Note: snd_dma_buffer_sync() is called for normal audio playback and
+        *       capture streams also.
+        */
+       snd_dma_buffer_sync(&sdev->dmatb, SNDRV_DMA_SYNC_CPU);
        /* copy available trace data to debugfs */
        rem = copy_to_user(buffer, ((u8 *)(dfse->buf) + lpos), count);
        if (rem)
@@ -464,8 +471,9 @@ int snd_sof_init_trace(struct snd_sof_dev *sdev)
        }
 
        /* allocate trace data buffer */
-       ret = snd_dma_alloc_pages(SNDRV_DMA_TYPE_DEV_SG, sdev->dev,
-                                 DMA_BUF_SIZE_FOR_TRACE, &sdev->dmatb);
+       ret = snd_dma_alloc_dir_pages(SNDRV_DMA_TYPE_DEV_SG, sdev->dev,
+                                     DMA_FROM_DEVICE, DMA_BUF_SIZE_FOR_TRACE,
+                                     &sdev->dmatb);
        if (ret < 0) {
                dev_err(sdev->dev,
                        "error: can't alloc buffer for trace %d\n", ret);