Re: [PATCH v3 1/3] dma: Support multiple interleaved frames with non-contiguous memory

[Lars-Peter Clausen <lars@xxxxxxxxxx>]

On 02/17/2014 10:29 AM, Srikanth Thokala wrote:
> On Mon, Feb 17, 2014 at 2:13 PM, Vinod Koul <vinod.koul@xxxxxxxxx> wrote:
> > On Sat, Feb 15, 2014 at 05:30:17PM +0530, Srikanth Thokala wrote:
> > > The current implementation of interleaved DMA API support multiple
> > > frames only when the memory is contiguous by incrementing src_start/
> > > dst_start members of interleaved template.
> > >
> > > But, when the memory is non-contiguous it will restrict slave device
> > > to not submit multiple frames in a batch.  This patch handles this
> > > issue by allowing the slave device to send array of interleaved dma
> > > templates each having a different memory location.
> > This seems to be missing the numbers of templates you are sending, wouldnt this
> > require sending ARRAY_SiZE too?
> >
> > And why send double pointer?
>
> Array size is not required, when we pass the double pointer.  The last
> element would be
> pointed to NULL and we could get the number of templates from this condition.
> Here is an example snippet,
>
> In slave device driver,
>
>          struct dma_interleaved_template **xts;
>
>          xts = kcalloc(frm_cnt+1, sizeof(struct
> dma_interleaved_template *), GFP_KERNEL);
>          /* Error check for xts */
>          for (i = 0; i < frm_cnt; i++) {
>                  xts[i] = kmalloc(sizeof(struct
> dma_interleaved_template), GFP_KERNEL);
>                  /* Error check for xts[i] */
>          }
>          xts[i] = NULL;
>
> In DMA engine driver,  we could get the number of frames by,
>
>          for (; xts[frmno] != NULL; frmno++);
>
> I felt this way is simpler than adding an extra argument to the API.
> Please let me know
> your opinion and suggest me a better way.

I think Vinod's suggestion of passing in an array of interleaved_templates 
and the size of the array is better than what you are currently doing.

Btw. you also need to update the current implementations and users of the 
API accordingly.

> > --
> > ~Vinod
> >
> > > Signed-off-by: Srikanth Thokala <sthokal@xxxxxxxxxx>
> > > ---
> > >   Documentation/dmaengine.txt              |    2 +-
> > >   drivers/dma/imx-dma.c                    |    3 ++-
> > >   drivers/dma/sirf-dma.c                   |    3 ++-
> > >   drivers/media/platform/m2m-deinterlace.c |    2 +-
> > >   include/linux/dmaengine.h                |    6 +++---
> > >   5 files changed, 9 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/Documentation/dmaengine.txt b/Documentation/dmaengine.txt
> > > index 879b6e3..c642614 100644
> > > --- a/Documentation/dmaengine.txt
> > > +++ b/Documentation/dmaengine.txt
> > > @@ -94,7 +94,7 @@ The slave DMA usage consists of following steps:
> > >                size_t period_len, enum dma_data_direction direction);
> > >
> > >        struct dma_async_tx_descriptor *(*device_prep_interleaved_dma)(
> > > -             struct dma_chan *chan, struct dma_interleaved_template *xt,
> > > +             struct dma_chan *chan, struct dma_interleaved_template **xts,
> > >                unsigned long flags);
> > >
> > >      The peripheral driver is expected to have mapped the scatterlist for
> > > diff --git a/drivers/dma/imx-dma.c b/drivers/dma/imx-dma.c
> > > index 6f9ac20..e2c52ce 100644
> > > --- a/drivers/dma/imx-dma.c
> > > +++ b/drivers/dma/imx-dma.c
> > > @@ -954,12 +954,13 @@ static struct dma_async_tx_descriptor *imxdma_prep_dma_memcpy(
> > >   }
> > >
> > >   static struct dma_async_tx_descriptor *imxdma_prep_dma_interleaved(
> > > -     struct dma_chan *chan, struct dma_interleaved_template *xt,
> > > +     struct dma_chan *chan, struct dma_interleaved_template **xts,
> > >        unsigned long flags)
> > >   {
> > >        struct imxdma_channel *imxdmac = to_imxdma_chan(chan);
> > >        struct imxdma_engine *imxdma = imxdmac->imxdma;
> > >        struct imxdma_desc *desc;
> > > +     struct dma_interleaved_template *xt = *xts;
> > >
> > >        dev_dbg(imxdma->dev, "%s channel: %d src_start=0x%llx dst_start=0x%llx\n"
> > >                "   src_sgl=%s dst_sgl=%s numf=%zu frame_size=%zu\n", __func__,
> > > diff --git a/drivers/dma/sirf-dma.c b/drivers/dma/sirf-dma.c
> > > index d4d3a31..b6a150b 100644
> > > --- a/drivers/dma/sirf-dma.c
> > > +++ b/drivers/dma/sirf-dma.c
> > > @@ -509,12 +509,13 @@ sirfsoc_dma_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
> > >   }
> > >
> > >   static struct dma_async_tx_descriptor *sirfsoc_dma_prep_interleaved(
> > > -     struct dma_chan *chan, struct dma_interleaved_template *xt,
> > > +     struct dma_chan *chan, struct dma_interleaved_template **xts,
> > >        unsigned long flags)
> > >   {
> > >        struct sirfsoc_dma *sdma = dma_chan_to_sirfsoc_dma(chan);
> > >        struct sirfsoc_dma_chan *schan = dma_chan_to_sirfsoc_dma_chan(chan);
> > >        struct sirfsoc_dma_desc *sdesc = NULL;
> > > +     struct dma_interleaved_template *xt = *xts;
> > >        unsigned long iflags;
> > >        int ret;
> > >
> > > diff --git a/drivers/media/platform/m2m-deinterlace.c b/drivers/media/platform/m2m-deinterlace.c
> > > index 6bb86b5..468110a 100644
> > > --- a/drivers/media/platform/m2m-deinterlace.c
> > > +++ b/drivers/media/platform/m2m-deinterlace.c
> > > @@ -343,7 +343,7 @@ static void deinterlace_issue_dma(struct deinterlace_ctx *ctx, int op,
> > >        ctx->xt->dst_sgl = true;
> > >        flags = DMA_CTRL_ACK | DMA_PREP_INTERRUPT;
> > >
> > > -     tx = dmadev->device_prep_interleaved_dma(chan, ctx->xt, flags);
> > > +     tx = dmadev->device_prep_interleaved_dma(chan, &ctx->xt, flags);
> > >        if (tx == NULL) {
> > >                v4l2_warn(&pcdev->v4l2_dev, "DMA interleaved prep error\n");
> > >                return;
> > > diff --git a/include/linux/dmaengine.h b/include/linux/dmaengine.h
> > > index c5c92d5..2f77a9a 100644
> > > --- a/include/linux/dmaengine.h
> > > +++ b/include/linux/dmaengine.h
> > > @@ -675,7 +675,7 @@ struct dma_device {
> > >                size_t period_len, enum dma_transfer_direction direction,
> > >                unsigned long flags, void *context);
> > >        struct dma_async_tx_descriptor *(*device_prep_interleaved_dma)(
> > > -             struct dma_chan *chan, struct dma_interleaved_template *xt,
> > > +             struct dma_chan *chan, struct dma_interleaved_template **xts,
> > >                unsigned long flags);
> > >        int (*device_control)(struct dma_chan *chan, enum dma_ctrl_cmd cmd,
> > >                unsigned long arg);
> > > @@ -752,10 +752,10 @@ static inline struct dma_async_tx_descriptor *dmaengine_prep_dma_cyclic(
> > >   }
> > >
> > >   static inline struct dma_async_tx_descriptor *dmaengine_prep_interleaved_dma(
> > > -             struct dma_chan *chan, struct dma_interleaved_template *xt,
> > > +             struct dma_chan *chan, struct dma_interleaved_template **xts,
> > >                unsigned long flags)
> > >   {
> > > -     return chan->device->device_prep_interleaved_dma(chan, xt, flags);
> > > +     return chan->device->device_prep_interleaved_dma(chan, xts, flags);
> > >   }
> > >
> > >   static inline int dma_get_slave_caps(struct dma_chan *chan, struct dma_slave_caps *caps)
> > > --
> > > 1.7.9.5
> > >
> > > --
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