[PATCH v2 0/8] dmaengine: Add new API to combine onfiguration and descriptor preparation

Frank Li
2025-12-18T15:56:50Z

Previously, configuration and preparation required two separate calls. This
works well when configuration is done only once during initialization.

However, in cases where the burst length or source/destination address must
be adjusted for each transfer, calling two functions is verbose.

if (dmaengine_slave_config(chan, &sconf)) {
dev_err(dev, "DMA slave config fail\n");
return -EIO;
}

tx = dmaengine_prep_slave_single(chan, dma_local, len, dir, flags);

After new API added

tx = dmaengine_prep_config_single(chan, dma_local, len, dir, flags, &sconf);

Additional, prevous two calls requires additional locking to ensure both
steps complete atomically.

mutex_lock()
dmaengine_slave_config()
dmaengine_prep_slave_single()
mutex_unlock()

after new API added, mutex lock can be moved. See patch
nvmet: pci-epf: Use dmaengine_prep_config_single_safe() API

Signed-off-by: Frank Li <Frank.Li@nxp.com>
---
Changes in v2:
- Use name dmaengine_prep_config_single() and dmaengine_prep_config_sg()
- Add _safe version to avoid confuse, which needn't additional mutex.
- Update document/
- Update commit message. add () for function name. Use upcase for subject.
- Add more explain for remove lock.
- Link to v1: https://lore.kernel.org/r/20251208-dma_prep_config-v1-0-53490c5e1e2a@nxp.com

---
Frank Li (8):
dmaengine: Add API to combine configuration and preparation (sg and single)
PCI: endpoint: pci-epf-test: Use dmaenigne_prep_config_single() to simplify code
dmaengine: dw-edma: Use new .device_prep_config_sg() callback
dmaengine: dw-edma: Pass dma_slave_config to dw_edma_device_transfer()
nvmet: pci-epf: Remove unnecessary dmaengine_terminate_sync() on each DMA transfer
nvmet: pci-epf: Use dmaengine_prep_config_single_safe() API
PCI: epf-mhi: Use dmaengine_prep_config_single() to simplify code
crypto: atmel: Use dmaengine_prep_config_single() API

Documentation/driver-api/dmaengine/client.rst | 9 +++
drivers/crypto/atmel-aes.c | 10 +--
drivers/dma/dw-edma/dw-edma-core.c | 36 ++++++---
drivers/nvme/target/pci-epf.c | 21 ++----
drivers/pci/endpoint/functions/pci-epf-mhi.c | 52 ++++---------
drivers/pci/endpoint/functions/pci-epf-test.c | 8 +-
include/linux/dmaengine.h | 103 ++++++++++++++++++++++++--
7 files changed, 156 insertions(+), 83 deletions(-)
---
base-commit: 8f0b4cce4481fb22653697cced8d0d04027cb1e8
change-id: 20251204-dma_prep_config-654170d245a2

Best regards,
--
Frank Li <Frank.Li@nxp.com>