Re: [PATCH v3 01/34] dmaengine: add tasklet-backed channel BH helpers

[Frank Li]

On Mon, Aug 10, 2026 at 11:09:02AM -0700, Allen Pais wrote:
> DMAengine drivers commonly use a per-channel tasklet to invoke client
> callbacks. Add helpers that initialize, schedule, and kill a channel
> bottom half, with an initial tasklet-backed implementation that preserves
> the existing execution context.
>
> Convert virt-dma to the new API and remove its private tasklet. Update all
> drivers that directly kill or override that tasklet in the same change so
> no stale users remain. While touching the completion handler, avoid forming
> a result pointer from a NULL cyclic descriptor.
>
> This establishes a backend-independent API before changing how channel
> bottom halves are dispatched.
>
> Signed-off-by: Allen Pais <allen.lkml@xxxxxxxxx>
> ---

Reviewed-by: Frank Li <Frank.Li@xxxxxxx>

>  drivers/dma/bcm2835-dma.c                     |  2 +-
>  drivers/dma/dma-axi-dmac.c                    | 10 +++--
>  drivers/dma/dma-jz4780.c                      |  2 +-
>  drivers/dma/dmaengine.c                       | 42 +++++++++++++++++++
>  .../dma/dw-axi-dmac/dw-axi-dmac-platform.c    |  2 +-
>  drivers/dma/dw-edma/dw-edma-core.c            |  2 +-
>  drivers/dma/fsl-edma-common.c                 |  2 +-
>  drivers/dma/fsl-qdma.c                        |  2 +-
>  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-sdma.c                        |  4 +-
>  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/owl-dma.c                         |  2 +-
>  drivers/dma/pxa_dma.c                         |  2 +-
>  drivers/dma/qcom/bam_dma.c                    |  4 +-
>  drivers/dma/qcom/qcom_adm.c                   |  4 +-
>  drivers/dma/sa11x0-dma.c                      |  2 +-
>  drivers/dma/sf-pdma/sf-pdma.c                 |  2 +-
>  drivers/dma/sprd-dma.c                        |  2 +-
>  drivers/dma/st_fdma.c                         |  2 +-
>  drivers/dma/sun6i-dma.c                       |  2 +-
>  drivers/dma/tegra186-gpc-dma.c                |  2 +-
>  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/virt-dma.c                        | 12 +++---
>  drivers/dma/virt-dma.h                        |  7 ++--
>  include/linux/dmaengine.h                     | 28 +++++++++++++
>  35 files changed, 125 insertions(+), 54 deletions(-)
>
> diff --git a/drivers/dma/bcm2835-dma.c b/drivers/dma/bcm2835-dma.c
> index 06d830d36882..c8add249dbfb 100644
> --- a/drivers/dma/bcm2835-dma.c
> +++ b/drivers/dma/bcm2835-dma.c
> @@ -829,7 +829,7 @@ static void bcm2835_dma_free(struct bcm2835_dmadev *od)
>  	list_for_each_entry_safe(c, next, &od->ddev.channels,
>  				 vc.chan.device_node) {
>  		list_del(&c->vc.chan.device_node);
> -		tasklet_kill(&c->vc.task);
> +		dmaengine_kill_bh(&c->vc.chan);
>  	}
>
>  	dma_unmap_page_attrs(od->ddev.dev, od->zero_page, PAGE_SIZE,
> diff --git a/drivers/dma/dma-axi-dmac.c b/drivers/dma/dma-axi-dmac.c
> index d47ff27e1408..d245d04c3a27 100644
> --- a/drivers/dma/dma-axi-dmac.c
> +++ b/drivers/dma/dma-axi-dmac.c
> @@ -1195,9 +1195,11 @@ static int axi_dmac_detect_caps(struct axi_dmac *dmac, unsigned int version)
>  	return 0;
>  }
>
> -static void axi_dmac_tasklet_kill(void *task)
> +static void axi_dmac_kill_bh(void *data)
>  {
> -	tasklet_kill(task);
> +	struct dma_chan *chan = data;
> +
> +	dmaengine_kill_bh(chan);
>  }
>
>  static void axi_dmac_free_dma_controller(void *of_node)
> @@ -1302,8 +1304,8 @@ static int axi_dmac_probe(struct platform_device *pdev)
>  	 * Put the action in here so it get's done before unregistering the DMA
>  	 * device.
>  	 */
> -	ret = devm_add_action_or_reset(&pdev->dev, axi_dmac_tasklet_kill,
> -				       &dmac->chan.vchan.task);
> +	ret = devm_add_action_or_reset(&pdev->dev, axi_dmac_kill_bh,
> +				       &dmac->chan.vchan.chan);
>  	if (ret)
>  		return ret;
>
> diff --git a/drivers/dma/dma-jz4780.c b/drivers/dma/dma-jz4780.c
> index 6070dfdb7114..738801501e29 100644
> --- a/drivers/dma/dma-jz4780.c
> +++ b/drivers/dma/dma-jz4780.c
> @@ -1019,7 +1019,7 @@ static void jz4780_dma_remove(struct platform_device *pdev)
>  	free_irq(jzdma->irq, jzdma);
>
>  	for (i = 0; i < jzdma->soc_data->nb_channels; i++)
> -		tasklet_kill(&jzdma->chan[i].vchan.task);
> +		dmaengine_kill_bh(&jzdma->chan[i].vchan.chan);
>  }
>
>  static const struct jz4780_dma_soc_data jz4740_dma_soc_data = {
> diff --git a/drivers/dma/dmaengine.c b/drivers/dma/dmaengine.c
> index 9049171df857..d8fc7eb71b48 100644
> --- a/drivers/dma/dmaengine.c
> +++ b/drivers/dma/dmaengine.c
> @@ -1428,6 +1428,48 @@ static void dmaengine_destroy_unmap_pool(void)
>  	}
>  }
>
> +static void dma_chan_bh_entry(struct tasklet_struct *tasklet)
> +{
> +	struct dma_chan *chan = from_tasklet(chan, tasklet, bh_tasklet);
> +	dmaengine_bh_work_fn fn = READ_ONCE(chan->bh_work_fn);
> +
> +	if (fn)
> +		fn(chan);
> +}
> +
> +void dmaengine_init_bh(struct dma_chan *chan, dmaengine_bh_work_fn fn)
> +{
> +	if (WARN_ON(!fn))
> +		return;
> +
> +	if (WARN_ON(chan->bh_work_initialized))
> +		return;
> +
> +	chan->bh_work_fn = fn;
> +	tasklet_setup(&chan->bh_tasklet, dma_chan_bh_entry);
> +	chan->bh_work_initialized = true;
> +}
> +EXPORT_SYMBOL_GPL(dmaengine_init_bh);
> +
> +bool dmaengine_schedule_bh(struct dma_chan *chan)
> +{
> +	if (WARN_ON(!chan->bh_work_initialized))
> +		return false;
> +
> +	tasklet_schedule(&chan->bh_tasklet);
> +	return true;
> +}
> +EXPORT_SYMBOL_GPL(dmaengine_schedule_bh);
> +
> +void dmaengine_kill_bh(struct dma_chan *chan)
> +{
> +	if (!chan->bh_work_initialized)
> +		return;
> +
> +	tasklet_kill(&chan->bh_tasklet);
> +}
> +EXPORT_SYMBOL_GPL(dmaengine_kill_bh);
> +
>  static int __init dmaengine_init_unmap_pool(void)
>  {
>  	int i;
> diff --git a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> index bcefaff03b5c..a2b688e7f47e 100644
> --- a/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> +++ b/drivers/dma/dw-axi-dmac/dw-axi-dmac-platform.c
> @@ -1663,7 +1663,7 @@ static void dw_remove(struct platform_device *pdev)
>  	list_for_each_entry_safe(chan, _chan, &dw->dma.channels,
>  				 vc.chan.device_node) {
>  		list_del(&chan->vc.chan.device_node);
> -		tasklet_kill(&chan->vc.task);
> +		dmaengine_kill_bh(&chan->vc.chan);
>  	}
>  }
>
> diff --git a/drivers/dma/dw-edma/dw-edma-core.c b/drivers/dma/dw-edma/dw-edma-core.c
> index 89a4c498a17b..ade866fba2ad 100644
> --- a/drivers/dma/dw-edma/dw-edma-core.c
> +++ b/drivers/dma/dw-edma/dw-edma-core.c
> @@ -1170,7 +1170,7 @@ int dw_edma_remove(struct dw_edma_chip *chip)
>  	dma_async_device_unregister(&dw->dma);
>  	list_for_each_entry_safe(chan, _chan, &dw->dma.channels,
>  				 vc.chan.device_node) {
> -		tasklet_kill(&chan->vc.task);
> +		dmaengine_kill_bh(&chan->vc.chan);
>  		list_del(&chan->vc.chan.device_node);
>  	}
>
> diff --git a/drivers/dma/fsl-edma-common.c b/drivers/dma/fsl-edma-common.c
> index bb7531c456df..90ae678c68d4 100644
> --- a/drivers/dma/fsl-edma-common.c
> +++ b/drivers/dma/fsl-edma-common.c
> @@ -915,7 +915,7 @@ void fsl_edma_cleanup_vchan(struct dma_device *dmadev)
>  	list_for_each_entry_safe(chan, _chan,
>  				&dmadev->channels, vchan.chan.device_node) {
>  		list_del(&chan->vchan.chan.device_node);
> -		tasklet_kill(&chan->vchan.task);
> +		dmaengine_kill_bh(&chan->vchan.chan);
>  	}
>  }
>
> diff --git a/drivers/dma/fsl-qdma.c b/drivers/dma/fsl-qdma.c
> index df843fad0ece..b0ace8bad498 100644
> --- a/drivers/dma/fsl-qdma.c
> +++ b/drivers/dma/fsl-qdma.c
> @@ -1255,7 +1255,7 @@ static void fsl_qdma_cleanup_vchan(struct dma_device *dmadev)
>  	list_for_each_entry_safe(chan, _chan,
>  				 &dmadev->channels, vchan.chan.device_node) {
>  		list_del(&chan->vchan.chan.device_node);
> -		tasklet_kill(&chan->vchan.task);
> +		dmaengine_kill_bh(&chan->vchan.chan);
>  	}
>  }
>
> diff --git a/drivers/dma/hisi_dma.c b/drivers/dma/hisi_dma.c
> index 28bf818f9aa6..10eb98350b9f 100644
> --- a/drivers/dma/hisi_dma.c
> +++ b/drivers/dma/hisi_dma.c
> @@ -720,7 +720,7 @@ static void hisi_dma_disable_qps(struct hisi_dma_dev *hdma_dev)
>
>  	for (i = 0; i < hdma_dev->chan_num; i++) {
>  		hisi_dma_disable_qp(hdma_dev, i);
> -		tasklet_kill(&hdma_dev->chan[i].vc.task);
> +		dmaengine_kill_bh(&hdma_dev->chan[i].vc.chan);
>  	}
>  }
>
> diff --git a/drivers/dma/hsu/hsu.c b/drivers/dma/hsu/hsu.c
> index f62d60d7bc6b..315d0ebecd57 100644
> --- a/drivers/dma/hsu/hsu.c
> +++ b/drivers/dma/hsu/hsu.c
> @@ -500,7 +500,7 @@ int hsu_dma_remove(struct hsu_dma_chip *chip)
>  	for (i = 0; i < hsu->nr_channels; i++) {
>  		struct hsu_dma_chan *hsuc = &hsu->chan[i];
>
> -		tasklet_kill(&hsuc->vchan.task);
> +		dmaengine_kill_bh(&hsuc->vchan.chan);
>  	}
>
>  	return 0;
> diff --git a/drivers/dma/idma64.c b/drivers/dma/idma64.c
> index 5fcd1befc92d..1d395fb735ff 100644
> --- a/drivers/dma/idma64.c
> +++ b/drivers/dma/idma64.c
> @@ -617,14 +617,14 @@ static void idma64_remove(struct idma64_chip *chip)
>
>  	/*
>  	 * Explicitly call devm_request_irq() to avoid the side effects with
> -	 * the scheduled tasklets.
> +	 * scheduled BH work.
>  	 */
>  	devm_free_irq(chip->dev, chip->irq, idma64);
>
>  	for (i = 0; i < idma64->dma.chancnt; i++) {
>  		struct idma64_chan *idma64c = &idma64->chan[i];
>
> -		tasklet_kill(&idma64c->vchan.task);
> +		dmaengine_kill_bh(&idma64c->vchan.chan);
>  	}
>  }
>
> diff --git a/drivers/dma/img-mdc-dma.c b/drivers/dma/img-mdc-dma.c
> index b3765ba15803..0c6024088444 100644
> --- a/drivers/dma/img-mdc-dma.c
> +++ b/drivers/dma/img-mdc-dma.c
> @@ -1031,7 +1031,7 @@ static void mdc_dma_remove(struct platform_device *pdev)
>
>  		devm_free_irq(&pdev->dev, mchan->irq, mchan);
>
> -		tasklet_kill(&mchan->vc.task);
> +		dmaengine_kill_bh(&mchan->vc.chan);
>  	}
>
>  	pm_runtime_disable(&pdev->dev);
> diff --git a/drivers/dma/imx-sdma.c b/drivers/dma/imx-sdma.c
> index 36368835a845..4d13b9d2880d 100644
> --- a/drivers/dma/imx-sdma.c
> +++ b/drivers/dma/imx-sdma.c
> @@ -2399,11 +2399,11 @@ static void sdma_remove(struct platform_device *pdev)
>  	int i;
>
>  	devm_free_irq(&pdev->dev, sdma->irq, sdma);
> -	/* Kill the tasklet */
> +	/* Kill the channel BH */
>  	for (i = 0; i < MAX_DMA_CHANNELS; i++) {
>  		struct sdma_channel *sdmac = &sdma->channel[i];
>
> -		tasklet_kill(&sdmac->vc.task);
> +		dmaengine_kill_bh(&sdmac->vc.chan);
>  		sdma_free_chan_resources(&sdmac->vc.chan);
>  	}
>
> diff --git a/drivers/dma/k3dma.c b/drivers/dma/k3dma.c
> index e84f197fea76..3d73b391e42e 100644
> --- a/drivers/dma/k3dma.c
> +++ b/drivers/dma/k3dma.c
> @@ -976,7 +976,7 @@ static void k3_dma_remove(struct platform_device *op)
>
>  	list_for_each_entry_safe(c, cn, &d->slave.channels, vc.chan.device_node) {
>  		list_del(&c->vc.chan.device_node);
> -		tasklet_kill(&c->vc.task);
> +		dmaengine_kill_bh(&c->vc.chan);
>  	}
>  	tasklet_kill(&d->task);
>  	clk_disable_unprepare(d->clk);
> diff --git a/drivers/dma/loongson/loongson1-apb-dma.c b/drivers/dma/loongson/loongson1-apb-dma.c
> index 89786cbd20ab..52a360719644 100644
> --- a/drivers/dma/loongson/loongson1-apb-dma.c
> +++ b/drivers/dma/loongson/loongson1-apb-dma.c
> @@ -552,7 +552,7 @@ static void ls1x_dma_chan_remove(struct ls1x_dma *dma)
>
>  		if (chan->vc.chan.device == &dma->ddev) {
>  			list_del(&chan->vc.chan.device_node);
> -			tasklet_kill(&chan->vc.task);
> +			dmaengine_kill_bh(&chan->vc.chan);
>  		}
>  	}
>  }
> diff --git a/drivers/dma/mediatek/mtk-cqdma.c b/drivers/dma/mediatek/mtk-cqdma.c
> index 80791e30aec2..7b44d3358cda 100644
> --- a/drivers/dma/mediatek/mtk-cqdma.c
> +++ b/drivers/dma/mediatek/mtk-cqdma.c
> @@ -895,7 +895,7 @@ static void mtk_cqdma_remove(struct platform_device *pdev)
>  		vc = &cqdma->vc[i];
>
>  		list_del(&vc->vc.chan.device_node);
> -		tasklet_kill(&vc->vc.task);
> +		dmaengine_kill_bh(&vc->vc.chan);
>  	}
>
>  	/* disable interrupt */
> diff --git a/drivers/dma/mediatek/mtk-hsdma.c b/drivers/dma/mediatek/mtk-hsdma.c
> index a43412ff5edd..75555fa41536 100644
> --- a/drivers/dma/mediatek/mtk-hsdma.c
> +++ b/drivers/dma/mediatek/mtk-hsdma.c
> @@ -1020,7 +1020,7 @@ static void mtk_hsdma_remove(struct platform_device *pdev)
>  		vc = &hsdma->vc[i];
>
>  		list_del(&vc->vc.chan.device_node);
> -		tasklet_kill(&vc->vc.task);
> +		dmaengine_kill_bh(&vc->vc.chan);
>  	}
>
>  	/* Disable DMA interrupt */
> diff --git a/drivers/dma/mediatek/mtk-uart-apdma.c b/drivers/dma/mediatek/mtk-uart-apdma.c
> index c269d84d7bd2..8ce206a0ecc5 100644
> --- a/drivers/dma/mediatek/mtk-uart-apdma.c
> +++ b/drivers/dma/mediatek/mtk-uart-apdma.c
> @@ -312,7 +312,7 @@ static void mtk_uart_apdma_free_chan_resources(struct dma_chan *chan)
>
>  	free_irq(c->irq, chan);
>
> -	tasklet_kill(&c->vc.task);
> +	dmaengine_kill_bh(&c->vc.chan);
>
>  	vchan_free_chan_resources(&c->vc);
>
> @@ -463,7 +463,7 @@ static void mtk_uart_apdma_free(struct mtk_uart_apdmadev *mtkd)
>  			struct mtk_chan, vc.chan.device_node);
>
>  		list_del(&c->vc.chan.device_node);
> -		tasklet_kill(&c->vc.task);
> +		dmaengine_kill_bh(&c->vc.chan);
>  	}
>  }
>
> diff --git a/drivers/dma/owl-dma.c b/drivers/dma/owl-dma.c
> index 7c80572fc71d..0d9f324adba0 100644
> --- a/drivers/dma/owl-dma.c
> +++ b/drivers/dma/owl-dma.c
> @@ -1055,7 +1055,7 @@ static inline void owl_dma_free(struct owl_dma *od)
>  	list_for_each_entry_safe(vchan,
>  				 next, &od->dma.channels, vc.chan.device_node) {
>  		list_del(&vchan->vc.chan.device_node);
> -		tasklet_kill(&vchan->vc.task);
> +		dmaengine_kill_bh(&vchan->vc.chan);
>  	}
>  }
>
> diff --git a/drivers/dma/pxa_dma.c b/drivers/dma/pxa_dma.c
> index fa2ee0b3e09f..2cca8c31929c 100644
> --- a/drivers/dma/pxa_dma.c
> +++ b/drivers/dma/pxa_dma.c
> @@ -1215,7 +1215,7 @@ static void pxad_free_channels(struct dma_device *dmadev)
>  	list_for_each_entry_safe(c, cn, &dmadev->channels,
>  				 vc.chan.device_node) {
>  		list_del(&c->vc.chan.device_node);
> -		tasklet_kill(&c->vc.task);
> +		dmaengine_kill_bh(&c->vc.chan);
>  	}
>  }
>
> diff --git a/drivers/dma/qcom/bam_dma.c b/drivers/dma/qcom/bam_dma.c
> index 1bb26af0405f..c23496c3ac69 100644
> --- a/drivers/dma/qcom/bam_dma.c
> +++ b/drivers/dma/qcom/bam_dma.c
> @@ -1387,7 +1387,7 @@ static int bam_dma_probe(struct platform_device *pdev)
>  	dma_async_device_unregister(&bdev->common);
>  err_bam_channel_exit:
>  	for (i = 0; i < bdev->num_channels; i++)
> -		tasklet_kill(&bdev->channels[i].vc.task);
> +		dmaengine_kill_bh(&bdev->channels[i].vc.chan);
>  err_tasklet_kill:
>  	tasklet_kill(&bdev->task);
>  err_disable_clk:
> @@ -1413,7 +1413,7 @@ static void bam_dma_remove(struct platform_device *pdev)
>
>  	for (i = 0; i < bdev->num_channels; i++) {
>  		bam_dma_terminate_all(&bdev->channels[i].vc.chan);
> -		tasklet_kill(&bdev->channels[i].vc.task);
> +		dmaengine_kill_bh(&bdev->channels[i].vc.chan);
>
>  		if (!bdev->channels[i].fifo_virt)
>  			continue;
> diff --git a/drivers/dma/qcom/qcom_adm.c b/drivers/dma/qcom/qcom_adm.c
> index 07fbe32d31fa..13f5ca8ff808 100644
> --- a/drivers/dma/qcom/qcom_adm.c
> +++ b/drivers/dma/qcom/qcom_adm.c
> @@ -918,8 +918,8 @@ static void adm_dma_remove(struct platform_device *pdev)
>  		/* mask IRQs for this channel/EE pair */
>  		writel(0, adev->regs + ADM_CH_RSLT_CONF(achan->id, adev->ee));
>
> -		tasklet_kill(&adev->channels[i].vc.task);
> -		adm_terminate_all(&adev->channels[i].vc.chan);
> +		dmaengine_kill_bh(&achan->vc.chan);
> +		adm_terminate_all(&achan->vc.chan);
>  	}
>
>  	devm_free_irq(adev->dev, adev->irq, adev);
> diff --git a/drivers/dma/sa11x0-dma.c b/drivers/dma/sa11x0-dma.c
> index a6fa431530e3..e14566fa2d74 100644
> --- a/drivers/dma/sa11x0-dma.c
> +++ b/drivers/dma/sa11x0-dma.c
> @@ -891,7 +891,7 @@ static void sa11x0_dma_free_channels(struct dma_device *dmadev)
>
>  	list_for_each_entry_safe(c, cn, &dmadev->channels, vc.chan.device_node) {
>  		list_del(&c->vc.chan.device_node);
> -		tasklet_kill(&c->vc.task);
> +		dmaengine_kill_bh(&c->vc.chan);
>  		kfree(c);
>  	}
>  }
> diff --git a/drivers/dma/sf-pdma/sf-pdma.c b/drivers/dma/sf-pdma/sf-pdma.c
> index 6f79cc28703e..a08ca355dadb 100644
> --- a/drivers/dma/sf-pdma/sf-pdma.c
> +++ b/drivers/dma/sf-pdma/sf-pdma.c
> @@ -602,7 +602,7 @@ static void sf_pdma_remove(struct platform_device *pdev)
>  		devm_free_irq(&pdev->dev, ch->txirq, ch);
>  		devm_free_irq(&pdev->dev, ch->errirq, ch);
>  		list_del(&ch->vchan.chan.device_node);
> -		tasklet_kill(&ch->vchan.task);
> +		dmaengine_kill_bh(&ch->vchan.chan);
>  		tasklet_kill(&ch->done_tasklet);
>  		tasklet_kill(&ch->err_tasklet);
>  	}
> diff --git a/drivers/dma/sprd-dma.c b/drivers/dma/sprd-dma.c
> index 087fea3af2e4..f90f5d8d5a1e 100644
> --- a/drivers/dma/sprd-dma.c
> +++ b/drivers/dma/sprd-dma.c
> @@ -1253,7 +1253,7 @@ static void sprd_dma_remove(struct platform_device *pdev)
>  	list_for_each_entry_safe(c, cn, &sdev->dma_dev.channels,
>  				 vc.chan.device_node) {
>  		list_del(&c->vc.chan.device_node);
> -		tasklet_kill(&c->vc.task);
> +		dmaengine_kill_bh(&c->vc.chan);
>  	}
>
>  	of_dma_controller_free(pdev->dev.of_node);
> diff --git a/drivers/dma/st_fdma.c b/drivers/dma/st_fdma.c
> index d9547017f3bd..cae0a7fe6ceb 100644
> --- a/drivers/dma/st_fdma.c
> +++ b/drivers/dma/st_fdma.c
> @@ -733,7 +733,7 @@ static void st_fdma_free(struct st_fdma_dev *fdev)
>  	for (i = 0; i < fdev->nr_channels; i++) {
>  		fchan = &fdev->chans[i];
>  		list_del(&fchan->vchan.chan.device_node);
> -		tasklet_kill(&fchan->vchan.task);
> +		dmaengine_kill_bh(&fchan->vchan.chan);
>  	}
>  }
>
> diff --git a/drivers/dma/sun6i-dma.c b/drivers/dma/sun6i-dma.c
> index f47a326dd7ff..4ddea3cdcd66 100644
> --- a/drivers/dma/sun6i-dma.c
> +++ b/drivers/dma/sun6i-dma.c
> @@ -1094,7 +1094,7 @@ static inline void sun6i_dma_free(struct sun6i_dma_dev *sdev)
>  		struct sun6i_vchan *vchan = &sdev->vchans[i];
>
>  		list_del(&vchan->vc.chan.device_node);
> -		tasklet_kill(&vchan->vc.task);
> +		dmaengine_kill_bh(&vchan->vc.chan);
>  	}
>  }
>
> diff --git a/drivers/dma/tegra186-gpc-dma.c b/drivers/dma/tegra186-gpc-dma.c
> index 64cedef1050a..3a27a83a3288 100644
> --- a/drivers/dma/tegra186-gpc-dma.c
> +++ b/drivers/dma/tegra186-gpc-dma.c
> @@ -1284,7 +1284,7 @@ static void tegra_dma_free_chan_resources(struct dma_chan *dc)
>  	tegra_dma_terminate_all(dc);
>  	synchronize_irq(tdc->irq);
>
> -	tasklet_kill(&tdc->vc.task);
> +	dmaengine_kill_bh(&tdc->vc.chan);
>  	tdc->config_init = false;
>  	tdc->slave_id = -1;
>  	tdc->sid_dir = DMA_TRANS_NONE;
> diff --git a/drivers/dma/tegra210-adma.c b/drivers/dma/tegra210-adma.c
> index ceaee1e33e68..780863199224 100644
> --- a/drivers/dma/tegra210-adma.c
> +++ b/drivers/dma/tegra210-adma.c
> @@ -811,7 +811,7 @@ static void tegra_adma_free_chan_resources(struct dma_chan *dc)
>
>  	tegra_adma_terminate_all(dc);
>  	vchan_free_chan_resources(&tdc->vc);
> -	tasklet_kill(&tdc->vc.task);
> +	dmaengine_kill_bh(&tdc->vc.chan);
>  	free_irq(tdc->irq, tdc);
>  	pm_runtime_put(tdc2dev(tdc));
>
> diff --git a/drivers/dma/ti/edma.c b/drivers/dma/ti/edma.c
> index d97db5af3555..c0ad0cdabb87 100644
> --- a/drivers/dma/ti/edma.c
> +++ b/drivers/dma/ti/edma.c
> @@ -2560,7 +2560,7 @@ static void edma_cleanupp_vchan(struct dma_device *dmadev)
>  	list_for_each_entry_safe(echan, _echan,
>  			&dmadev->channels, vchan.chan.device_node) {
>  		list_del(&echan->vchan.chan.device_node);
> -		tasklet_kill(&echan->vchan.task);
> +		dmaengine_kill_bh(&echan->vchan.chan);
>  	}
>  }
>
> diff --git a/drivers/dma/ti/k3-udma.c b/drivers/dma/ti/k3-udma.c
> index 1cf158eb7bdb..fd428c26799a 100644
> --- a/drivers/dma/ti/k3-udma.c
> +++ b/drivers/dma/ti/k3-udma.c
> @@ -4042,12 +4042,12 @@ static void udma_desc_pre_callback(struct virt_dma_chan *vc,
>  }
>
>  /*
> - * This tasklet handles the completion of a DMA descriptor by
> + * This BH handles the completion of a DMA descriptor by
>   * calling its callback and freeing it.
>   */
> -static void udma_vchan_complete(struct tasklet_struct *t)
> +static void udma_vchan_complete(struct dma_chan *chan)
>  {
> -	struct virt_dma_chan *vc = from_tasklet(vc, t, task);
> +	struct virt_dma_chan *vc = to_virt_chan(chan);
>  	struct virt_dma_desc *vd, *_vd;
>  	struct dmaengine_desc_callback cb;
>  	LIST_HEAD(head);
> @@ -4112,7 +4112,7 @@ static void udma_free_chan_resources(struct dma_chan *chan)
>  	}
>
>  	vchan_free_chan_resources(&uc->vc);
> -	tasklet_kill(&uc->vc.task);
> +	dmaengine_kill_bh(&uc->vc.chan);
>
>  	bcdma_free_bchan_resources(uc);
>  	udma_free_tx_resources(uc);
> @@ -5627,8 +5627,8 @@ static int udma_probe(struct platform_device *pdev)
>  		if (!uc->name)
>  			return -ENOMEM;
>  		vchan_init(&uc->vc, &ud->ddev);
> -		/* Use custom vchan completion handling */
> -		tasklet_setup(&uc->vc.task, udma_vchan_complete);
> +		/* Override the default vchan completion handler */
> +		uc->vc.chan.bh_work_fn = udma_vchan_complete;
>  		init_completion(&uc->teardown_completed);
>  		INIT_DELAYED_WORK(&uc->tx_drain.work, udma_check_tx_completion);
>  	}
> diff --git a/drivers/dma/ti/omap-dma.c b/drivers/dma/ti/omap-dma.c
> index 55ece7fd0d99..899c5eeeac88 100644
> --- a/drivers/dma/ti/omap-dma.c
> +++ b/drivers/dma/ti/omap-dma.c
> @@ -1521,7 +1521,7 @@ static void omap_dma_free(struct omap_dmadev *od)
>  			struct omap_chan, vc.chan.device_node);
>
>  		list_del(&c->vc.chan.device_node);
> -		tasklet_kill(&c->vc.task);
> +		dmaengine_kill_bh(&c->vc.chan);
>  		kfree(c);
>  	}
>  }
> diff --git a/drivers/dma/virt-dma.c b/drivers/dma/virt-dma.c
> index 7961172a780d..d407af6cc1da 100644
> --- a/drivers/dma/virt-dma.c
> +++ b/drivers/dma/virt-dma.c
> @@ -77,12 +77,12 @@ struct virt_dma_desc *vchan_find_desc(struct virt_dma_chan *vc,
>  EXPORT_SYMBOL_GPL(vchan_find_desc);
>
>  /*
> - * This tasklet handles the completion of a DMA descriptor by
> - * calling its callback and freeing it.
> + * This bottom-half handler completes a DMA descriptor by invoking its
> + * callback and freeing it.
>   */
> -static void vchan_complete(struct tasklet_struct *t)
> +static void vchan_complete(struct dma_chan *chan)
>  {
> -	struct virt_dma_chan *vc = from_tasklet(vc, t, task);
> +	struct virt_dma_chan *vc = to_virt_chan(chan);
>  	struct virt_dma_desc *vd, *_vd;
>  	struct dmaengine_desc_callback cb;
>  	LIST_HEAD(head);
> @@ -98,7 +98,7 @@ static void vchan_complete(struct tasklet_struct *t)
>  	}
>  	spin_unlock_irq(&vc->lock);
>
> -	dmaengine_desc_callback_invoke(&cb, &vd->tx_result);
> +	dmaengine_desc_callback_invoke(&cb, vd ? &vd->tx_result : NULL);
>
>  	list_for_each_entry_safe(vd, _vd, &head, node) {
>  		dmaengine_desc_get_callback(&vd->tx, &cb);
> @@ -131,7 +131,7 @@ void vchan_init(struct virt_dma_chan *vc, struct dma_device *dmadev)
>  	INIT_LIST_HEAD(&vc->desc_completed);
>  	INIT_LIST_HEAD(&vc->desc_terminated);
>
> -	tasklet_setup(&vc->task, vchan_complete);
> +	dmaengine_init_bh(&vc->chan, vchan_complete);
>
>  	vc->chan.device = dmadev;
>  	list_add_tail(&vc->chan.device_node, &dmadev->channels);
> diff --git a/drivers/dma/virt-dma.h b/drivers/dma/virt-dma.h
> index 59d9eabc8b67..0ba42fded2cc 100644
> --- a/drivers/dma/virt-dma.h
> +++ b/drivers/dma/virt-dma.h
> @@ -21,7 +21,6 @@ struct virt_dma_desc {
>
>  struct virt_dma_chan {
>  	struct dma_chan	chan;
> -	struct tasklet_struct task;
>  	void (*desc_free)(struct virt_dma_desc *);
>
>  	spinlock_t lock;
> @@ -106,7 +105,7 @@ static inline void vchan_cookie_complete(struct virt_dma_desc *vd)
>  		 vd, cookie);
>  	list_add_tail(&vd->node, &vc->desc_completed);
>
> -	tasklet_schedule(&vc->task);
> +	dmaengine_schedule_bh(&vc->chan);
>  }
>
>  /**
> @@ -137,7 +136,7 @@ static inline void vchan_cyclic_callback(struct virt_dma_desc *vd)
>  	struct virt_dma_chan *vc = to_virt_chan(vd->tx.chan);
>
>  	vc->cyclic = vd;
> -	tasklet_schedule(&vc->task);
> +	dmaengine_schedule_bh(&vc->chan);
>  }
>
>  /**
> @@ -223,7 +222,7 @@ static inline void vchan_synchronize(struct virt_dma_chan *vc)
>  	LIST_HEAD(head);
>  	unsigned long flags;
>
> -	tasklet_kill(&vc->task);
> +	dmaengine_kill_bh(&vc->chan);
>
>  	spin_lock_irqsave(&vc->lock, flags);
>
> diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> index b3d251c9734e..a1437bdbda9b 100644
> --- a/include/linux/dmaengine.h
> +++ b/include/linux/dmaengine.h
> @@ -12,6 +12,7 @@
>  #include <linux/scatterlist.h>
>  #include <linux/bitmap.h>
>  #include <linux/types.h>
> +#include <linux/interrupt.h>
>  #include <asm/page.h>
>
>  /**
> @@ -295,6 +296,10 @@ enum dma_desc_metadata_mode {
>  	DESC_METADATA_ENGINE = BIT(1),
>  };
>
> +struct dma_chan;
> +
> +typedef void (*dmaengine_bh_work_fn)(struct dma_chan *chan);
> +
>  /**
>   * struct dma_chan_percpu - the per-CPU part of struct dma_chan
>   * @memcpy_count: transaction counter
> @@ -334,6 +339,9 @@ struct dma_router {
>   * @router: pointer to the DMA router structure
>   * @route_data: channel specific data for the router
>   * @private: private data for certain client-channel associations
> + * @bh_tasklet: bottom-half tasklet stored per-channel
> + * @bh_work_fn: callback executed when @bh_tasklet runs
> + * @bh_work_initialized: indicates whether @bh_tasklet has been initialized
>   */
>  struct dma_chan {
>  	struct dma_device *device;
> @@ -359,6 +367,9 @@ struct dma_chan {
>  	void *route_data;
>
>  	void *private;
> +	struct tasklet_struct bh_tasklet;
> +	dmaengine_bh_work_fn bh_work_fn;
> +	bool bh_work_initialized;
>  };
>
>  /**
> @@ -1529,6 +1540,9 @@ struct dma_chan *devm_dma_request_chan(struct device *dev, const char *name);
>
>  void dma_release_channel(struct dma_chan *chan);
>  int dma_get_slave_caps(struct dma_chan *chan, struct dma_slave_caps *caps);
> +void dmaengine_init_bh(struct dma_chan *chan, dmaengine_bh_work_fn fn);
> +bool dmaengine_schedule_bh(struct dma_chan *chan);
> +void dmaengine_kill_bh(struct dma_chan *chan);
>  #else
>  static inline struct dma_chan *dma_find_channel(enum dma_transaction_type tx_type)
>  {
> @@ -1576,6 +1590,20 @@ static inline int dma_get_slave_caps(struct dma_chan *chan,
>  {
>  	return -ENXIO;
>  }
> +
> +static inline void dmaengine_init_bh(struct dma_chan *chan,
> +				     dmaengine_bh_work_fn fn)
> +{
> +}
> +
> +static inline bool dmaengine_schedule_bh(struct dma_chan *chan)
> +{
> +	return false;
> +}
> +
> +static inline void dmaengine_kill_bh(struct dma_chan *chan)
> +{
> +}
>  #endif
>
>  static inline int dmaengine_desc_set_reuse(struct dma_async_tx_descriptor *tx)
> --
> 2.43.0
>