On Mon, Aug 10, 2026 at 11:09:01AM -0700, Allen Pais wrote:
> Hi Arnd, Vinod and Frank,
>
> This series moves DMAengine client completion bottom halves from private
> tasklets to a common per-channel API backed by WQ_BH.
>
> The first patch introduces the dmaengine_*_bh() API with a tasklet backend
> and converts virt-dma to it. It also updates every driver that directly
> accesses the removed virt_dma_chan tasklet, keeping the patch buildable on
> its own. This separates the driver-facing API from its implementation
> without changing callback context.
>
> The second patch switches that backend to a dedicated WQ_BH | WQ_PERCPU
> workqueue. WQ_BH keeps callbacks in softirq context, while the common API
> centralizes initialization, scheduling, and synchronization. The
> workqueue helpers remain internal to DMAengine, and dmaengine_kill_bh()
> drains scheduled callbacks to preserve tasklet_kill() semantics.
>
> The remaining patches convert driver-owned channel completion tasklets.
> Tasklets used for controller-level processing, recovery, or other
> non-client-callback work are deliberately left alone because the
> appropriate replacement may differ by driver.
>
> As agreed in the RFC discussion, selecting hardirq callback delivery is a
> separate API change and is not part of this series.
>
> Earlier discussion:
> https://lore.kernel.org/all/20260108080332.2341725-1-allen.lkml@gmail.com/
>
> v2:
> https://lore.kernel.org/all/cover.1785183549.git.allen.lkml@gmail.com/
>
> Changes since v2:
> - rename the new public helpers and callback type from dma_chan_* to
> dmaengine_* as requested by Vinod
> - update all direct virt_dma_chan tasklet users in patch 1, fixing the
> intermediate build failures reported by Sashiko
> - fold the resulting 30 empty teardown patches, reducing the series from
> 64 to 34 patches without dropping any driver changes
> - rebase from Linux 7.2-rc5 to d58772d8520c (latest Linus master)
>
> Review tags retained on unchanged standalone patches:
> - 09/34 IOAT: Acked-by Dave Jiang
> - 17/34 STE DMA40: Reviewed-by Linus Walleij
> - 27/34 PLX DMA and 34/34 Switchtec: Reviewed-by Logan Gunthorpe
>
> Review tags received on v2 patches now folded into 01/34:
> - v2 41/64 HSU: Reviewed-by Andy Shevchenko
> - v2 60/64 BAM DMA: Acked-by Bartosz Golaszewski
>
> The HSU and BAM DMA changes remain in 01/34, but those patch-specific
> trailers are not attached to the substantially broader 35-file patch.
> Andy and Bartosz are copied here and on 01/34 for visibility.
>
> Testing:
> - x86_64 olddefconfig, make -j$(nproc) W=1 drivers/dma/
> - the same DMA build with patch 1 applied independently
> - scripts/checkpatch.pl --strict on all 34 patches
>
> Allen Pais (34):
> dmaengine: add tasklet-backed channel BH helpers
> dmaengine: back channel BH helpers with WQ_BH
> dmaengine: apple-admac: use dmaengine BH callback
> dmaengine: at_xdmac: move irq bottom half to dmaengine BH
> dmaengine: ep93xx: hook callbacks via dmaengine BH
> dmaengine: fsldma: migrate tasklet to dmaengine BH
> dmaengine: fsl_raid: run completions via dmaengine BH
> dmaengine: imx-dma: flip per-chan tasklet to dmaengine BH
> dmaengine: ioat: convert cleanup tasklet to dmaengine BH
> dmaengine: mmp_pdma: replace per-chan tasklet with dmaengine BH
> dmaengine: mmp_tdma: hook completions to dmaengine BH
> dmaengine: mv_xor: convert irq tasklet to dmaengine BH
> dmaengine: mxs-dma: use dmaengine BH scheduling
> dmaengine: nbpfaxi: switch callbacks to dmaengine BH
> dmaengine: pch_dma: convert tasklet to dmaengine BH
> dmaengine: ppc4xx: replace irq tasklet with dmaengine BH
> dmaengine: ste_dma40: convert per-channel tasklet to dmaengine BH
> dmaengine: xgene-dma: wire descriptor cleanup to dmaengine BH
> dmaengine: xilinx-dma: use dmaengine BH instead of tasklets
> dmaengine: xilinx-dpdma: kill vchan BH on remove
> dmaengine: zynqmp-dma: switch completion tasklet to dmaengine BH
> dmaengine: tegra20-apb: use channel BH helpers
> dmaengine: timb_dma: route callbacks via channel BH
> dmaengine: txx9dmac: route callbacks via channel BH
> dmaengine: mv_xor_v2: use channel BH helpers
> dmaengine: mpc512x: route callbacks via channel BH
> dmaengine: plx_dma: use channel BH helpers
> dmaengine: sf-pdma: route error callbacks through channel BH
> dmaengine: pl330: route callbacks via channel BH
> dmaengine: altera-msgdma: use channel BH helpers
> dmaengine: dw: defer callbacks via channel BH
> dmaengine: hidma: defer callbacks via channel BH
> dmaengine: qcom-gpi: defer callbacks via vchan
> dmaengine: switchtec: use channel BH helpers
>
> drivers/dma/altera-msgdma.c | 14 +--
> drivers/dma/apple-admac.c | 16 ++--
> drivers/dma/at_xdmac.c | 13 ++-
> drivers/dma/bcm2835-dma.c | 2 +-
> drivers/dma/dma-axi-dmac.c | 10 ++-
> drivers/dma/dma-jz4780.c | 2 +-
> drivers/dma/dmaengine.c | 89 ++++++++++++++++++-
> .../dma/dw-axi-dmac/dw-axi-dmac-platform.c | 2 +-
> drivers/dma/dw-edma/dw-edma-core.c | 2 +-
> drivers/dma/dw/core.c | 42 +++++++--
> drivers/dma/dw/regs.h | 1 +
> drivers/dma/ep93xx_dma.c | 12 ++-
> drivers/dma/fsl-edma-common.c | 2 +-
> drivers/dma/fsl-qdma.c | 2 +-
> drivers/dma/fsl_raid.c | 11 +--
> drivers/dma/fsl_raid.h | 1 -
> drivers/dma/fsldma.c | 10 +--
> drivers/dma/fsldma.h | 1 -
> drivers/dma/hisi_dma.c | 2 +-
> drivers/dma/hsu/hsu.c | 2 +-
> drivers/dma/idma64.c | 4 +-
> drivers/dma/img-mdc-dma.c | 2 +-
> drivers/dma/imx-dma.c | 26 +++---
> drivers/dma/imx-sdma.c | 4 +-
> drivers/dma/ioat/dma.c | 14 +--
> drivers/dma/ioat/dma.h | 3 +-
> drivers/dma/ioat/init.c | 2 +-
> drivers/dma/k3dma.c | 2 +-
> drivers/dma/loongson/loongson1-apb-dma.c | 2 +-
> drivers/dma/mediatek/mtk-cqdma.c | 2 +-
> drivers/dma/mediatek/mtk-hsdma.c | 2 +-
> drivers/dma/mediatek/mtk-uart-apdma.c | 4 +-
> drivers/dma/mmp_pdma.c | 13 ++-
> drivers/dma/mmp_tdma.c | 9 +-
> drivers/dma/mpc512x_dma.c | 74 +++++++++------
> drivers/dma/mv_xor.c | 12 +--
> drivers/dma/mv_xor.h | 2 -
> drivers/dma/mv_xor_v2.c | 20 ++---
> drivers/dma/mxs-dma.c | 11 ++-
> drivers/dma/nbpfaxi.c | 13 ++-
> drivers/dma/owl-dma.c | 2 +-
> drivers/dma/pch_dma.c | 14 +--
> drivers/dma/pl330.c | 18 ++--
> drivers/dma/plx_dma.c | 12 +--
> drivers/dma/ppc4xx/adma.c | 14 +--
> drivers/dma/ppc4xx/adma.h | 2 -
> drivers/dma/pxa_dma.c | 2 +-
> drivers/dma/qcom/bam_dma.c | 4 +-
> drivers/dma/qcom/gpi.c | 17 +++-
> drivers/dma/qcom/hidma.c | 18 +++-
> drivers/dma/qcom/qcom_adm.c | 4 +-
> drivers/dma/sa11x0-dma.c | 2 +-
> drivers/dma/sf-pdma/sf-pdma.c | 14 ++-
> drivers/dma/sprd-dma.c | 2 +-
> drivers/dma/st_fdma.c | 2 +-
> drivers/dma/ste_dma40.c | 13 ++-
> drivers/dma/sun6i-dma.c | 2 +-
> drivers/dma/switchtec_dma.c | 16 ++--
> drivers/dma/tegra186-gpc-dma.c | 2 +-
> drivers/dma/tegra20-apb-dma.c | 18 ++--
> drivers/dma/tegra210-adma.c | 2 +-
> drivers/dma/ti/edma.c | 2 +-
> drivers/dma/ti/k3-udma.c | 12 +--
> drivers/dma/ti/omap-dma.c | 2 +-
> drivers/dma/timb_dma.c | 21 +++--
> drivers/dma/txx9dmac.c | 12 +--
> drivers/dma/txx9dmac.h | 1 -
> drivers/dma/virt-dma.c | 12 +--
> drivers/dma/virt-dma.h | 7 +-
> drivers/dma/xgene-dma.c | 19 ++--
> drivers/dma/xilinx/xilinx_dma.c | 20 ++---
> drivers/dma/xilinx/xilinx_dpdma.c | 1 +
> drivers/dma/xilinx/zynqmp_dma.c | 19 ++--
There are some dmaengine code out of drivers/dma tree. Do you plan to
convert it also
Frank
> include/linux/dmaengine.h | 28 ++++++
> 74 files changed, 482 insertions(+), 311 deletions(-)
>
> --
> 2.43.0