ASoC: SOF: ipc4-pcm: fix start offset calculation for chain DMA

Assumption that chain DMA module starts the link DMA when 1ms of
data is available from host is not correct. Instead the firmware
chain DMA module fills the link DMA with initial buffer of zeroes
and the host and link DMAs are started at the same time.

This results in a small error in delay calculation. This can become a
more severe problem if host DMA has delays that exceed 1ms. This results
in negative delay to be calculated and bogus values reported to
applications. This can confuse some applications like
alsa_conformance_test.

Fix the issue by correctly calculating the firmware chain DMA
preamble size and initializing the start offset to this value.

Cc: stable@vger.kernel.org
Fixes: a1d203d390e0 ("ASoC: SOF: ipc4-pcm: Enable delay reporting for ChainDMA streams")
Signed-off-by: Kai Vehmanen <kai.vehmanen@linux.intel.com>
Reviewed-by: Péter Ujfalusi <peter.ujfalusi@linux.intel.com>
Reviewed-by: Bard Liao <yung-chuan.liao@linux.intel.com>
Signed-off-by: Peter Ujfalusi <peter.ujfalusi@linux.intel.com>
Link: https://patch.msgid.link/20251002074719.2084-3-peter.ujfalusi@linux.intel.com
Signed-off-by: Mark Brown <broonie@kernel.org>

diff --git a/sound/soc/sof/ipc4-pcm.c b/sound/soc/sof/ipc4-pcm.c
index 769ba4fed56a9565b1504235c04b67e7099f91f2..9d29d2e56c00863f069461eb236a5f2933a5a88d 100644 (file)
--- a/sound/soc/sof/ipc4-pcm.c
+++ b/sound/soc/sof/ipc4-pcm.c
@@ -1108,7 +1108,7 @@ static int sof_ipc4_get_stream_start_offset(struct snd_sof_dev *sdev,
                return -EINVAL;
        } else if (host_copier->data.gtw_cfg.node_id == SOF_IPC4_CHAIN_DMA_NODE_ID) {
                /*
-                * While the firmware does not supports time_info reporting for
+                * While the firmware does not support time_info reporting for
                 * streams using ChainDMA, it is granted that ChainDMA can only
                 * be used on Host+Link pairs where the link position is
                 * accessible from the host side.
@@ -1116,10 +1116,16 @@ static int sof_ipc4_get_stream_start_offset(struct snd_sof_dev *sdev,
                 * Enable delay calculation in case of ChainDMA via host
                 * accessible registers.
                 *
-                * The ChainDMA uses 2x 1ms ping-pong buffer, dai side starts
-                * when 1ms data is available
+                * The ChainDMA prefills the link DMA with a preamble
+                * of zero samples. Set the stream start offset based
+                * on size of the preamble (driver provided fifo size
+                * multiplied by 2.5). We add 1ms of margin as the FW
+                * will align the buffer size to DMA hardware
+                * alignment that is not known to host.
                 */
-               time_info->stream_start_offset = substream->runtime->rate / MSEC_PER_SEC;
+               int pre_ms = SOF_IPC4_CHAIN_DMA_BUF_SIZE_MS * 5 / 2 + 1;
+
+               time_info->stream_start_offset = pre_ms * substream->runtime->rate / MSEC_PER_SEC;
                goto out;
        }
 

diff --git a/sound/soc/sof/ipc4-topology.c b/sound/soc/sof/ipc4-topology.c
index b6a732d0adb4b7be8b73a9e51278ea11744c1611..36568160f163961f27b117029b0ff366e9705d7f 100644 (file)
--- a/sound/soc/sof/ipc4-topology.c
+++ b/sound/soc/sof/ipc4-topology.c
@@ -33,7 +33,6 @@ MODULE_PARM_DESC(ipc4_ignore_cpc,
 
 #define SOF_IPC4_GAIN_PARAM_ID  0
 #define SOF_IPC4_TPLG_ABI_SIZE 6
-#define SOF_IPC4_CHAIN_DMA_BUF_SIZE_MS 2
 
 static DEFINE_IDA(alh_group_ida);
 static DEFINE_IDA(pipeline_ida);

diff --git a/sound/soc/sof/ipc4-topology.h b/sound/soc/sof/ipc4-topology.h
index dfa1a6c2ffa8293b2aed3f5fe0db92ace14c4377..6b29692dff165d4f859ff07812eaa46add62774c 100644 (file)
--- a/sound/soc/sof/ipc4-topology.h
+++ b/sound/soc/sof/ipc4-topology.h
@@ -263,6 +263,8 @@ struct sof_ipc4_dma_stream_ch_map {
 #define SOF_IPC4_DMA_METHOD_HDA   1
 #define SOF_IPC4_DMA_METHOD_GPDMA 2 /* defined for consistency but not used */
 
+#define SOF_IPC4_CHAIN_DMA_BUF_SIZE_MS 2
+
 /**
  * struct sof_ipc4_dma_config: DMA configuration
  * @dma_method: HDAudio or GPDMA