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Tue, 10 Nov 2026 05:15:22 -0800 (PST) Received: from cryptic.lan ([2001:569:7077:be00:8191:2bfc:aa6d:704b]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-3b16769b589sm3806975a91.5.2026.11.10.05.15.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 10 Nov 2026 05:15:22 -0800 (PST) From: Allen Pais To: Vinod Koul Cc: Allen Pais , Frank Li , Arnd Bergmann , Andy Shevchenko , Bartosz Golaszewski , Dave Jiang , Linus Walleij , Logan Gunthorpe , dmaengine@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v4 00/33] dmaengine: migrate channel tasklets to WQ_BH Date: Tue, 10 Nov 2026 05:13:00 -0800 Message-ID: X-Mailer: git-send-email 2.43.0 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Hi Vinod, Frank and Arnd, 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. Frank asked about DMAengine users outside drivers/dma/ that still open-code completion tasklets. Those will be converted in a follow-up series once this one has landed, to keep this set from growing further. 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/ v3: https://lore.kernel.org/all/cover.1786384168.git.allen.lkml@gmail.com/ Changes since v3: - post as a new thread instead of in reply to v3 (Andy) - rebase onto v7.4-rc2. The ste_dma40 rework merged for 7.4-rc1 added tasklet_schedule() calls in the d40_queue_start() error paths and a devm action that kills the channel tasklets; both now use the BH helpers. fsldma and mv_xor gained tasklet_kill() calls in their channel remove and error paths, which are converted as well. zynqmp_dma and altera-msgdma only needed context fixes. The new amlogic-dma driver and the new at_hdmac channel cleanup path kill the virt-dma channel tasklet directly and are converted in 01/33. - drop the DW DMA patch (v3 31/34). Andy considers it unneeded churn ahead of a larger cleanup of that driver. - pl330: initialize the channel BH at probe time instead of in alloc_chan_resources(). dmaengine_init_bh() warns when called on an already initialized channel, and channels can be re-requested. - txx9dmac: channels served by the shared controller interrupt keep scanning descriptors from the controller tasklet. v3 scheduled a BH that was never initialized for them. - timb_dma: recompute TIMBDMA_IER from the channel BH once the channel has been finished, and drain the channel BHs on remove and in the probe error path. - mpc512x: drain the channel BHs in mpc_dma_remove(). - sf-pdma: reset the retry budget when abandoning a descriptor, and spell out in the changelog how the new error path mirrors the done tasklet (Frank). - hidma: leave hidma_free() unchanged (Frank). Drain the BH in free_chan_resources() and in remove(), after killing the low-level completion tasklet and before hidma_ll_uninit(), and add a device_synchronize() callback. - qcom-gpi: synchronize the vchan before the channel ring is freed, and add a device_synchronize() callback. - collect Frank Li's Reviewed-by from v3. I kept it on patches that only picked up mechanical conversions from the rebase (01, 06, 12, 17, 21, 27, 30). timb_dma, txx9dmac, mpc512x, pl330 and qcom-gpi changed enough that I have not carried his tag forward on those. The driver changes above came out of going through the Sashiko reports on v3. Most of what it flagged are pre-existing teardown and locking issues in the individual drivers that this series does not make worse; those are out of scope here. Review tags retained on unchanged standalone patches: - 09/33 IOAT: Acked-by Dave Jiang - 17/33 STE DMA40: Reviewed-by Linus Walleij (the rebase only added the mechanical conversions mentioned above) - 27/33 PLX DMA and 33/33 Switchtec: Reviewed-by Logan Gunthorpe Review tags received on v2 patches now folded into 01/33: - 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 01/33, but those patch-specific trailers are not attached to the substantially broader 37-file patch. Andy and Bartosz are copied here and on 01/33 for visibility. Testing: - build-tested on top of v7.4-rc2 with W=1 for drivers/dma/, with no new warnings compared to the base commit: - arm64, x86_64 and arm allmodconfig - powerpc 44x/katmai_defconfig + AMCC_PPC440SPE_ADMA, mpc512x_defconfig + MPC512X_DMA, mpc85xx_smp_defconfig + FSL_DMA, and the same with FSL_DMA replaced by FSL_RAID - mips rbtx49xx_defconfig + TXX9_DMAC - every patch builds on its own (drivers/dma/) with the arm64 and x86_64 allmodconfig configurations - the series also applies cleanly on dmaengine/next (currently v7.4-rc1) - scripts/checkpatch.pl --strict is clean on all 33 patches - the sf-pdma and hidma changes are compile-tested only; testing on hardware would be appreciated Allen Pais (33): 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: 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/amlogic-dma.c | 4 +- drivers/dma/apple-admac.c | 16 ++-- drivers/dma/at_hdmac.c | 2 +- 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/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 | 12 +-- 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 | 78 ++++++++++------ drivers/dma/mv_xor.c | 14 +-- 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 | 19 ++-- 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 | 27 +++++- drivers/dma/qcom/hidma.c | 24 ++++- drivers/dma/qcom/qcom_adm.c | 4 +- drivers/dma/sa11x0-dma.c | 2 +- drivers/dma/sf-pdma/sf-pdma.c | 18 +++- drivers/dma/sprd-dma.c | 2 +- drivers/dma/st_fdma.c | 2 +- drivers/dma/ste_dma40.c | 29 +++--- 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 | 41 +++++++-- drivers/dma/txx9dmac.c | 10 +-- 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 ++-- include/linux/dmaengine.h | 28 ++++++ 74 files changed, 503 insertions(+), 316 deletions(-) base-commit: 7475ea8b58616b33c04afb976cf0fbaad9dd63fb -- 2.43.0