Re: [PATCH 2/9] dma: Convert from tasklet to BH workqueue

Allen
2024-03-28T17:50:03Z

>
> Subsytem is dmaengine, can you rename this to dmaengine: ...

My apologies, will have it fixed in v2.

>
> On 27-03-24, 16:03, Allen Pais wrote:
> > The only generic interface to execute asynchronously in the BH context is
> > tasklet; however, it's marked deprecated and has some design flaws. To
> > replace tasklets, BH workqueue support was recently added. A BH workqueue
> > behaves similarly to regular workqueues except that the queued work items
> > are executed in the BH context.
>
> Thanks for conversion, am happy with BH alternative as it helps in
> dmaengine where we need shortest possible time between tasklet and
> interrupt handling to maximize dma performance
>
> >
> > This patch converts drivers/dma/* from tasklet to BH workqueue.
>
> >
> > Based on the work done by Tejun Heo <tj@kernel.org>
> > Branch: git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq.git for-6.10
> >
> > Signed-off-by: Allen Pais <allen.lkml@gmail.com>
> > ---
> > drivers/dma/altera-msgdma.c | 15 ++++----
> > drivers/dma/apple-admac.c | 15 ++++----
> > drivers/dma/at_hdmac.c | 2 +-
> > drivers/dma/at_xdmac.c | 15 ++++----
> > drivers/dma/bcm2835-dma.c | 2 +-
> > drivers/dma/dma-axi-dmac.c | 2 +-
> > drivers/dma/dma-jz4780.c | 2 +-
> > .../dma/dw-axi-dmac/dw-axi-dmac-platform.c | 2 +-
> > drivers/dma/dw-edma/dw-edma-core.c | 2 +-
> > drivers/dma/dw/core.c | 13 +++----
> > drivers/dma/dw/regs.h | 3 +-
> > drivers/dma/ep93xx_dma.c | 15 ++++----
> > drivers/dma/fsl-edma-common.c | 2 +-
> > drivers/dma/fsl-qdma.c | 2 +-
> > drivers/dma/fsl_raid.c | 11 +++---
> > drivers/dma/fsl_raid.h | 2 +-
> > drivers/dma/fsldma.c | 15 ++++----
> > drivers/dma/fsldma.h | 3 +-
> > 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 | 27 +++++++-------
> > drivers/dma/imx-sdma.c | 6 ++--
> > drivers/dma/ioat/dma.c | 17 ++++-----
> > drivers/dma/ioat/dma.h | 5 +--
> > drivers/dma/ioat/init.c | 2 +-
> > drivers/dma/k3dma.c | 19 +++++-----
> > drivers/dma/mediatek/mtk-cqdma.c | 35 ++++++++++---------
> > 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 | 11 +++---
> > drivers/dma/mpc512x_dma.c | 17 ++++-----
> > drivers/dma/mv_xor.c | 13 +++----
> > drivers/dma/mv_xor.h | 5 +--
> > drivers/dma/mv_xor_v2.c | 23 ++++++------
> > drivers/dma/mxs-dma.c | 13 +++----
> > drivers/dma/nbpfaxi.c | 15 ++++----
> > drivers/dma/owl-dma.c | 2 +-
> > drivers/dma/pch_dma.c | 17 ++++-----
> > drivers/dma/pl330.c | 31 ++++++++--------
> > drivers/dma/plx_dma.c | 13 +++----
> > drivers/dma/ppc4xx/adma.c | 17 ++++-----
> > drivers/dma/ppc4xx/adma.h | 5 +--
> > drivers/dma/pxa_dma.c | 2 +-
> > drivers/dma/qcom/bam_dma.c | 35 ++++++++++---------
> > drivers/dma/qcom/gpi.c | 18 +++++-----
> > drivers/dma/qcom/hidma.c | 11 +++---
> > drivers/dma/qcom/hidma.h | 5 +--
> > drivers/dma/qcom/hidma_ll.c | 11 +++---
> > drivers/dma/qcom/qcom_adm.c | 2 +-
> > drivers/dma/sa11x0-dma.c | 27 +++++++-------
> > drivers/dma/sf-pdma/sf-pdma.c | 23 ++++++------
> > drivers/dma/sf-pdma/sf-pdma.h | 5 +--
> > drivers/dma/sprd-dma.c | 2 +-
> > drivers/dma/st_fdma.c | 2 +-
> > drivers/dma/ste_dma40.c | 17 ++++-----
> > drivers/dma/sun6i-dma.c | 33 ++++++++---------
> > drivers/dma/tegra186-gpc-dma.c | 2 +-
> > drivers/dma/tegra20-apb-dma.c | 19 +++++-----
> > drivers/dma/tegra210-adma.c | 2 +-
> > drivers/dma/ti/edma.c | 2 +-
> > drivers/dma/ti/k3-udma.c | 11 +++---
> > drivers/dma/ti/omap-dma.c | 2 +-
> > drivers/dma/timb_dma.c | 23 ++++++------
> > drivers/dma/txx9dmac.c | 29 +++++++--------
> > drivers/dma/txx9dmac.h | 5 +--
> > drivers/dma/virt-dma.c | 9 ++---
> > drivers/dma/virt-dma.h | 9 ++---
> > drivers/dma/xgene-dma.c | 21 +++++------
> > drivers/dma/xilinx/xilinx_dma.c | 23 ++++++------
> > drivers/dma/xilinx/xilinx_dpdma.c | 21 +++++------
> > drivers/dma/xilinx/zynqmp_dma.c | 21 +++++------
> > 74 files changed, 442 insertions(+), 395 deletions(-)
> >
> > diff --git a/drivers/dma/altera-msgdma.c b/drivers/dma/altera-msgdma.c
> > index a8e3615235b8..611b5290324b 100644
> > --- a/drivers/dma/altera-msgdma.c
> > +++ b/drivers/dma/altera-msgdma.c
> > @@ -20,6 +20,7 @@
> > #include <linux/platform_device.h>
> > #include <linux/slab.h>
> > #include <linux/of_dma.h>
> > +#include <linux/workqueue.h>
> >
> > #include "dmaengine.h"
> >
> > @@ -170,7 +171,7 @@ struct msgdma_sw_desc {
> > struct msgdma_device {
> > spinlock_t lock;
> > struct device *dev;
> > - struct tasklet_struct irq_tasklet;
> > + struct work_struct irq_work;
>
> Can we name these as bh_work to signify that we are always in bh
> context? here and everywhere please

Sure, will address it in v2.
>
>
> > struct list_head pending_list;
> > struct list_head free_list;
> > struct list_head active_list;
> > @@ -676,12 +677,12 @@ static int msgdma_alloc_chan_resources(struct dma_chan *dchan)
> > }
> >
> > /**
> > - * msgdma_tasklet - Schedule completion tasklet
> > + * msgdma_work - Schedule completion work
>
> ..
>
> > @@ -515,7 +516,7 @@ struct gpii {
> > enum gpi_pm_state pm_state;
> > rwlock_t pm_lock;
> > struct gpi_ring ev_ring;
> > - struct tasklet_struct ev_task; /* event processing tasklet */
> > + struct work_struct ev_task; /* event processing work */
> > struct completion cmd_completion;
> > enum gpi_cmd gpi_cmd;
> > u32 cntxt_type_irq_msk;
> > @@ -755,7 +756,7 @@ static void gpi_process_ieob(struct gpii *gpii)
> > gpi_write_reg(gpii, gpii->ieob_clr_reg, BIT(0));
> >
> > gpi_config_interrupts(gpii, MASK_IEOB_SETTINGS, 0);
> > - tasklet_hi_schedule(&gpii->ev_task);
> > + queue_work(system_bh_highpri_wq, &gpii->ev_task);
>
> This is good conversion, thanks for ensuring system_bh_highpri_wq is
> used here

Thank you very much for the review, will have v2 sent soon.

- Allen

> --
> ~Vinod
>