[PATCH v2 0/4] dmaengine: dw: serialize completion and termination

[James Hilliard <james.hilliard1@gmail.com>]

Keep descriptor callbacks in the controller tasklet and serialize the
ownership changes used by completion, error recovery and termination.
This lets device_synchronize wait for callbacks while preserving tasklet
scheduling requests from other active channels.

The first two patches carry Serge Semin's fixes [0], with unchanged code
and the collected review trailers. They make tx_status calculate residue
without invoking callbacks [1], clear stopped-channel interrupts and keep
normal completion-list updates under the channel lock [2].

The third patch fixes error recovery separately: recheck the error under
the channel lock, stop the channel and detach the failed descriptor before
starting queued work. The fourth adds synchronization using
tasklet_disable()/tasklet_enable(), preserving pending tasklet runs while
waiting for an executing callback.

[0] https://lore.kernel.org/r/20240911184710.4207-1-fancer.lancer@gmail.com
[1] https://patch.msgid.link/20240911184710.4207-2-fancer.lancer@gmail.com
[2] https://patch.msgid.link/20240911184710.4207-3-fancer.lancer@gmail.com

Assisted-by: Codex:gpt-6-astra
Signed-off-by: James Hilliard <james.hilliard1@gmail.com>

---
Changes in v2:
- Carry Serge Semin's two posted fixes before the synchronization change,
  preserving his authorship and revision notes. Add the requested stable
  Cc trailers and Andy Shevchenko's Tested-by tags to those unchanged fixes.
- Add a separate error-recovery fix for stale error status, empty channel
  lists and software-LLP state when terminating or restarting a channel.
- Use tasklet_disable()/tasklet_enable() instead of tasklet_kill() so
  synchronization preserves scheduling requests from other channels.
- Explain descriptor ownership during termination and acknowledge the
  shared-tasklet scheduling race reported by Sashiko.
- Link to v1: https://patch.msgid.link/20261021-submit-dw-dma-synchronize-v1-v1-1-6af85c2d6f69@gmail.com

Revision history from Serge's series:

Link: https://lore.kernel.org/dmaengine/20240802080756.7415-1-fancer.lancer@gmail.com/
Changelog RFC:
- Add a new patch:
  [PATCH 2/2] dmaengine: dw: Fix XFER bit set, but channel not idle error
  fixing the "XFER bit set, but channel not idle" error.
- Instead of just dropping the dwc_scan_descriptors() method invocation
  calculate the residue in the Tx-status getter.

---
James Hilliard (2):
      dmaengine: dw: serialize error recovery with channel termination
      dmaengine: dw: synchronize completion callbacks

Serge Semin (2):
      dmaengine: dw: Prevent tx-status calling DMA-desc callback
      dmaengine: dw: Fix XFER bit set, but channel not idle error

 drivers/dma/dw/core.c | 180 +++++++++++++++++++++++++++++---------------------
 1 file changed, 103 insertions(+), 77 deletions(-)
---
base-commit: 93f51579e7df248780214094418f205253383cc5
change-id: 20261021-submit-dw-dma-synchronize-v1-e550f47fd1da

Best regards,
--  
James Hilliard <james.hilliard1@gmail.com>