[PATCH] ASoC: tas2781: Add delay before block checksum retry to prevent deadlock

[Zeliang Li]

During runtime resume from power-saving states, the tas2781 amplifier
firmware block calibration checksum verification may occasionally fail
due to transient instabilities on the I2C bus or the chip's internal
power rails.

When tasdev_block_chksum() detects a checksum mismatch, it correctly
decrements block->nr_retry and returns -EAGAIN to trigger a
re-transmission loop. However, because there is no delay introduced
before repeating the loop, all available retry attempts are exhausted
almost instantly (within microseconds) before the hardware can fully
stabilize. This causes a permanent calibration failure, triggering
"ERROR_PRAM_CRCCHK", and results in a silent speaker deadlock after
pausing/resuming media on modern laptops.

Fix this by adding a 2ms usleep_range() delay before initiating a
checksum re-try loop, allowing the hardware sufficient time to
stabilize.

Signed-off-by: Zeliang Li <lizeliang.linux@xxxxxxxxx>
---
 sound/soc/codecs/tas2781-fmwlib.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/sound/soc/codecs/tas2781-fmwlib.c
b/sound/soc/codecs/tas2781-fmwlib.c
index dcbeb9618195..09cbee7a55dc 100644
--- a/sound/soc/codecs/tas2781-fmwlib.c
+++ b/sound/soc/codecs/tas2781-fmwlib.c
@@ -1765,9 +1765,16 @@ static int tasdev_block_chksum(struct
tasdevice_priv *tas_priv,
  ret = -EAGAIN;
  block->nr_retry--;

- if (block->nr_retry <= 0)
+ if (block->nr_retry <= 0) {
  set_err_prg_cfg(block->type,
  &tas_priv->tasdevice[chn]);
+
+ } else {
+ /* Give the chip and I2C bus time to stabilize before
+ * next re-transmission attempt.
+ */
+ usleep_range(2000, 2500);
+ }
  } else
  tas_priv->tasdevice[chn].err_code &= ~ERROR_PRAM_CRCCHK;

-- 
2.53.0

-- 
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