linux-kernel - [PATCH 6/7] soundwire: cadence_master: add fake_size parameter to sdw_cdns_prepare_read_dma

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Message-ID: <20251014031450.3781789-7-yung-chuan.liao@linux.intel.com>
Date: Tue, 14 Oct 2025 11:14:49 +0800
From: Bard Liao <yung-chuan.liao@...ux.intel.com>
To: linux-sound@...r.kernel.org,
	vkoul@...nel.org
Cc: vinod.koul@...aro.org,
	linux-kernel@...r.kernel.org,
	pierre-louis.bossart@...ux.dev,
	bard.liao@...el.com
Subject: [PATCH 6/7] soundwire: cadence_master: add fake_size parameter to sdw_cdns_prepare_read_dma_buffer

We may need to add few fake frames to fit the aligned read dma buffer
size. Add a fake_size parameter to allow the caller to set the fake data
size.

Signed-off-by: Bard Liao <yung-chuan.liao@...ux.intel.com>
Reviewed-by: Ranjani Sridharan <ranjani.sridharan@...ux.intel.com>
---
 drivers/soundwire/cadence_master.c | 39 +++++++++++++++++++++++++++++-
 drivers/soundwire/cadence_master.h |  2 +-
 drivers/soundwire/intel_ace2x.c    |  2 +-
 3 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/drivers/soundwire/cadence_master.c b/drivers/soundwire/cadence_master.c
index 57671f9b3e9c..4e94da28d8ad 100644
--- a/drivers/soundwire/cadence_master.c
+++ b/drivers/soundwire/cadence_master.c
@@ -2393,7 +2393,7 @@ EXPORT_SYMBOL(sdw_cdns_prepare_write_dma_buffer);
 
 int sdw_cdns_prepare_read_dma_buffer(u8 dev_num, u32 start_register, int data_size,
 				     int data_per_frame, u8 *dma_buffer, int dma_buffer_size,
-				     int *dma_buffer_total_bytes)
+				     int *dma_buffer_total_bytes, unsigned int fake_size)
 {
 	int total_dma_data_written = 0;
 	u8 *p_dma_buffer = dma_buffer;
@@ -2445,6 +2445,43 @@ int sdw_cdns_prepare_read_dma_buffer(u8 dev_num, u32 start_register, int data_si
 		if (ret < 0)
 			return ret;
 
+		counter++;
+
+		p_dma_buffer += dma_data_written;
+		dma_buffer_size -= dma_data_written;
+		total_dma_data_written += dma_data_written;
+	}
+
+	/* Add fake frame */
+	header[0] &= ~GENMASK(7, 6);	/* Set inactive flag in BPT/BRA frame heade */
+	while (fake_size >= data_per_frame) {
+		header[1] = data_per_frame;
+		ret = sdw_cdns_prepare_read_pd0_buffer(header, SDW_CDNS_BRA_HDR, p_dma_buffer,
+						       dma_buffer_size, &dma_data_written,
+						       counter);
+		if (ret < 0)
+			return ret;
+
+		counter++;
+
+		fake_size -= data_per_frame;
+		p_dma_buffer += dma_data_written;
+		dma_buffer_size -= dma_data_written;
+		total_dma_data_written += dma_data_written;
+	}
+
+	if (fake_size) {
+		header[1] = fake_size;
+		ret = sdw_cdns_prepare_read_pd0_buffer(header, SDW_CDNS_BRA_HDR, p_dma_buffer,
+						       dma_buffer_size, &dma_data_written,
+						       counter);
+		if (ret < 0)
+			return ret;
+
+		counter++;
+
+		p_dma_buffer += dma_data_written;
+		dma_buffer_size -= dma_data_written;
 		total_dma_data_written += dma_data_written;
 	}
 
diff --git a/drivers/soundwire/cadence_master.h b/drivers/soundwire/cadence_master.h
index 6830d7f2d772..a269a87486fc 100644
--- a/drivers/soundwire/cadence_master.h
+++ b/drivers/soundwire/cadence_master.h
@@ -226,7 +226,7 @@ int sdw_cdns_prepare_write_dma_buffer(u8 dev_num, u32 start_register, u8 *data,
 
 int sdw_cdns_prepare_read_dma_buffer(u8 dev_num, u32 start_register, int data_size,
 				     int data_per_frame, u8 *dma_buffer, int dma_buffer_size,
-				     int *dma_buffer_total_bytes);
+				     int *dma_buffer_total_bytes, unsigned int fake_size);
 
 int sdw_cdns_check_write_response(struct device *dev, u8 *dma_buffer,
 				  int dma_buffer_size, int num_frames);
diff --git a/drivers/soundwire/intel_ace2x.c b/drivers/soundwire/intel_ace2x.c
index 5d08364ad6d1..22118b053d56 100644
--- a/drivers/soundwire/intel_ace2x.c
+++ b/drivers/soundwire/intel_ace2x.c
@@ -177,7 +177,7 @@ static int intel_ace2x_bpt_open_stream(struct sdw_intel *sdw, struct sdw_slave *
 		ret = sdw_cdns_prepare_read_dma_buffer(msg->dev_num, msg->addr,	msg->len,
 						       data_per_frame,
 						       sdw->bpt_ctx.dmab_tx_bdl.area,
-						       pdi0_buffer_size, &tx_total_bytes);
+						       pdi0_buffer_size, &tx_total_bytes, 0);
 	}
 
 	if (!ret)
-- 
2.43.0