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ASoC: SOF: ipc4-pcm: fix start offset calculation for chain DMA #5507

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Merged
ujfalusi merged 1 commit into from
Aug 25, 2025
Merged

ASoC: SOF: ipc4-pcm: fix start offset calculation for chain DMA #5507

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14 changes: 10 additions & 4 deletions sound/soc/sof/ipc4-pcm.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1068,18 +1068,24 @@ 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.
*
* 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;
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@kv2019i kv2019i Aug 11, 2025

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FW code calculates above as '2 * 5 / 2', convert to bytes and aligns up to DMA transfer size. We could calculate this exactly, but not sure if it will add value here.


time_info->stream_start_offset = pre_ms * substream->runtime->rate / MSEC_PER_SEC;
goto out;
}

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1 change: 0 additions & 1 deletion sound/soc/sof/ipc4-topology.c
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Expand Up @@ -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);
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2 changes: 2 additions & 0 deletions sound/soc/sof/ipc4-topology.h
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Expand Up @@ -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
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