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Date: Mon, 17 Feb 2014 10:44:42 +0100
From: Lars-Peter Clausen <lars@...afoo.de>
To: Srikanth Thokala <sthokal@...inx.com>
CC: Vinod Koul <vinod.koul@...el.com>, dan.j.williams@...el.com,
michal.simek@...inx.com, Grant Likely <grant.likely@...aro.org>,
robh+dt@...nel.org, Levente Kurusa <levex@...ux.com>,
andriy.shevchenko@...ux.jf.intel.com, dmaengine@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
devicetree@...r.kernel.org
Subject: Re: [PATCH v3 1/3] dma: Support multiple interleaved frames with
non-contiguous memory
On 02/17/2014 10:42 AM, Srikanth Thokala wrote:
> On Mon, Feb 17, 2014 at 3:05 PM, Lars-Peter Clausen <lars@...afoo.de> wrote:
>> On 02/17/2014 10:29 AM, Srikanth Thokala wrote:
>>>
>>> On Mon, Feb 17, 2014 at 2:13 PM, Vinod Koul <vinod.koul@...el.com> 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.
>
> Ok, Lars. I will update with this in my v4. Thanks.
>
>>
>> Btw. you also need to update the current implementations and users of the
>> API accordingly.
>
> Yes, I have updated them in this patch.
But you didn't update them accordingly to your proposed semantics. The
caller didn't NULL terminate the array and the drivers did blindly assume
there will always be exactly one transfer.
>
> Thanks
> Srikanth
>
>
>>
>>
>>>
>>>>
>>>> --
>>>> ~Vinod
>>>>
>>>>>
>>>>> Signed-off-by: Srikanth Thokala <sthokal@...inx.com>
>>>>> ---
>>>>> 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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>>>>
>>>>
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