Messages in this thread |  | | From | Frank Li <> | | Subject | [PATCH v4 0/9] dmaengine: Add new API to combine configuration and descriptor preparation | | Date | Wed, 06 May 2026 16:44:12 -0400 |
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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 v4: - remove void* context in config_prep() callback - use spin lock to protect config() and prep(). - Link to v3: https://lore.kernel.org/r/20260105-dma_prep_config-v3-0-a8480362fd42@nxp.com
Changes in v3: - collect review tags - create safe version in framework - Link to v2: https://lore.kernel.org/r/20251218-dma_prep_config-v2-0-c07079836128@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 (9): dmaengine: Add API to combine configuration and preparation (sg and single) dmaengine: Add safe API to combine configuration and preparation 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/dmaengine.c | 2 + drivers/dma/dw-edma/dw-edma-core.c | 41 ++++++--- 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 | 121 ++++++++++++++++++++++++-- 8 files changed, 180 insertions(+), 84 deletions(-) --- base-commit: b9303e6bff706758c167af686b5315ad00233bf8 change-id: 20251204-dma_prep_config-654170d245a2
Best regards, -- Frank Li <Frank.Li@nxp.com>
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