Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1542859 > unrolled thread

Re: [PATCH 2/3] dmaeninge: xilinx_dma: Fix bug in multiple frame stores scenario in vdma

Back to article view | Back to linux.kernel

This discussion starts older than the indexed window; earlier articles aren't shown. The article labeled Started by below is the oldest one visible, not the original post.

Contents

  Re: [PATCH 2/3] dmaeninge: xilinx_dma: Fix bug in multiple frame  stores scenario in vdma Jose Abreu <Jose.Abreu@synopsys.com> - 2016-12-15 17:20 +0100
    Re: [PATCH 2/3] dmaeninge: xilinx_dma: Fix bug in multiple frame  stores scenario in vdma Jose Abreu <Jose.Abreu@synopsys.com> - 2016-12-16 11:20 +0100

#1542859 — Re: [PATCH 2/3] dmaeninge: xilinx_dma: Fix bug in multiple frame stores scenario in vdma

Hi Kedar,


On 15-12-2016 15:11, Kedareswara rao Appana wrote:
> When VDMA is configured for more than one frame in the h/w
> for example h/w is configured for n number of frames and user
> Submits n number of frames and triggered the DMA using issue_pending API.
> In the current driver flow we are submitting one frame at a time
> but we should submit all the n number of frames at one time as the h/w
> Is configured for n number of frames.
>
> This patch fixes this issue.
>
> Signed-off-by: Kedareswara rao Appana <appanad@xilinx.com>
> ---
>  drivers/dma/xilinx/xilinx_dma.c | 43 +++++++++++++++++++++++++----------------
>  1 file changed, 26 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/dma/xilinx/xilinx_dma.c b/drivers/dma/xilinx/xilinx_dma.c
> index 736c2a3..4f3fa94 100644
> --- a/drivers/dma/xilinx/xilinx_dma.c
> +++ b/drivers/dma/xilinx/xilinx_dma.c
> @@ -1087,23 +1087,33 @@ static void xilinx_vdma_start_transfer(struct xilinx_dma_chan *chan)
>  				tail_segment->phys);
>  	} else {
>  		struct xilinx_vdma_tx_segment *segment, *last = NULL;
> -		int i = 0;
> +		int i = 0, j = 0;
>  
>  		if (chan->desc_submitcount < chan->num_frms)
>  			i = chan->desc_submitcount;
>  
> -		list_for_each_entry(segment, &desc->segments, node) {
> -			if (chan->ext_addr)
> -				vdma_desc_write_64(chan,
> -					XILINX_VDMA_REG_START_ADDRESS_64(i++),
> -					segment->hw.buf_addr,
> -					segment->hw.buf_addr_msb);
> -			else
> -				vdma_desc_write(chan,
> -					XILINX_VDMA_REG_START_ADDRESS(i++),
> -					segment->hw.buf_addr);
> -
> -			last = segment;
> +		for (j = 0; j < chan->num_frms; ) {
> +			list_for_each_entry(segment, &desc->segments, node) {
> +				if (chan->ext_addr)
> +					vdma_desc_write_64(chan,
> +					  XILINX_VDMA_REG_START_ADDRESS_64(i++),
> +					  segment->hw.buf_addr,
> +					  segment->hw.buf_addr_msb);
> +				else
> +					vdma_desc_write(chan,
> +					    XILINX_VDMA_REG_START_ADDRESS(i++),
> +					    segment->hw.buf_addr);
> +
> +				last = segment;

Hmm, is it possible to submit more than one segment? If so, then
i and j will get out of sync.

> +			}
> +			list_del(&desc->node);
> +			list_add_tail(&desc->node, &chan->active_list);
> +			j++;

But if i is non zero and pending_list has more than num_frms then
i will not wrap-around as it should and will write to invalid
framebuffer location, right?

> +			if (list_empty(&chan->pending_list))
> +				break;
> +			desc = list_first_entry(&chan->pending_list,
> +						struct xilinx_dma_tx_descriptor,
> +						node);
>  		}
>  
>  		if (!last)
> @@ -1114,14 +1124,13 @@ static void xilinx_vdma_start_transfer(struct xilinx_dma_chan *chan)
>  		vdma_desc_write(chan, XILINX_DMA_REG_FRMDLY_STRIDE,
>  				last->hw.stride);
>  		vdma_desc_write(chan, XILINX_DMA_REG_VSIZE, last->hw.vsize);

Maybe a check that all framebuffers contain valid addresses
should be done before programming vsize so that VDMA does not try
to write to invalid addresses.

> +
> +		chan->desc_submitcount += j;
> +		chan->desc_pendingcount -= j;
>  	}
>  
>  	chan->idle = false;
>  	if (!chan->has_sg) {
> -		list_del(&desc->node);
> -		list_add_tail(&desc->node, &chan->active_list);
> -		chan->desc_submitcount++;
> -		chan->desc_pendingcount--;
>  		if (chan->desc_submitcount == chan->num_frms)
>  			chan->desc_submitcount = 0;

"desc_submitcount >= chan->num_frms would be safer here.

>  	} else {

Best regards,
Jose Miguel Abreu

[toc] | [next] | [standalone]

#1543333

Hi Kedar,


On 15-12-2016 19:09, Appana Durga Kedareswara Rao wrote:
> Hi Jose Miguel Abreu,
>
> 	Thanks for the review....
>
>>> -			last = segment;
>>> +		for (j = 0; j < chan->num_frms; ) {
>>> +			list_for_each_entry(segment, &desc->segments, node)
>> {
>>> +				if (chan->ext_addr)
>>> +					vdma_desc_write_64(chan,
>>> +
>> XILINX_VDMA_REG_START_ADDRESS_64(i++),
>>> +					  segment->hw.buf_addr,
>>> +					  segment->hw.buf_addr_msb);
>>> +				else
>>> +					vdma_desc_write(chan,
>>> +
>> XILINX_VDMA_REG_START_ADDRESS(i++),
>>> +					    segment->hw.buf_addr);
>>> +
>>> +				last = segment;
>> Hmm, is it possible to submit more than one segment? If so, then i and j will get
>> out of sync.
> If h/w is configured for more than 1 frame buffer and user submits more than one frame buffer
> We can submit more than one frame/ segment to hw right??

I'm not sure. When I used VDMA driver I always submitted only one
segment and multiple descriptors. But the problem is, for example:

If you have:
descriptor1 (2 segments)
descriptor2 (2 segments)

And you have 3 frame buffers in the HW.

Then:
1st frame buffer will have: descriptor1 -> segment1
2nd frame buffer will have: descriptor1 -> segment2
3rd frame buffer will have: descriptor2 -> segment1
but, 4th frame buffer will have: descriptor2 -> segment2 <----
INVALID because there is only 3 frame buffers

So, maybe a check inside the loop "list_for_each_entry(segment,
&desc->segments, node)" could be a nice to have.

>
>>> +			}
>>> +			list_del(&desc->node);
>>> +			list_add_tail(&desc->node, &chan->active_list);
>>> +			j++;
>> But if i is non zero and pending_list has more than num_frms then i will not
>> wrap-around as it should and will write to invalid framebuffer location, right?
> Yep will fix in v2...
> 		
> 	If (if (list_empty(&chan->pending_list)) || (i == chan->num_frms)
> 		break;
>
> Above condition is sufficient right???

Looks ok.

>
>>> +			if (list_empty(&chan->pending_list))
>>> +				break;
>>> +			desc = list_first_entry(&chan->pending_list,
>>> +						struct
>> xilinx_dma_tx_descriptor,
>>> +						node);
>>>  		}
>>>
>>>  		if (!last)
>>> @@ -1114,14 +1124,13 @@ static void xilinx_vdma_start_transfer(struct
>> xilinx_dma_chan *chan)
>>>  		vdma_desc_write(chan, XILINX_DMA_REG_FRMDLY_STRIDE,
>>>  				last->hw.stride);
>>>  		vdma_desc_write(chan, XILINX_DMA_REG_VSIZE, last-
>>> hw.vsize);
>> Maybe a check that all framebuffers contain valid addresses should be done
>> before programming vsize so that VDMA does not try to write to invalid
>> addresses.
> Do we really need to check for valid address??? 
> I didn't get you what to do you mean by invalid address could you please explain???
> In the driver we are reading form the pending_list which will be updated by pep_interleaved_dma 
> Call so we are under assumption that user sends the proper address right???

What I mean by valid address is to check that i variable has
already been incremented by num_frms at least once since a VDMA
reset. This way you know that you have programmed all the
addresses of the frame buffers with an address and they are non-zero.

Best regards,
Jose Miguel Abreu

>
>>> +
>>> +		chan->desc_submitcount += j;
>>> +		chan->desc_pendingcount -= j;
>>>  	}
>>>
>>>  	chan->idle = false;
>>>  	if (!chan->has_sg) {
>>> -		list_del(&desc->node);
>>> -		list_add_tail(&desc->node, &chan->active_list);
>>> -		chan->desc_submitcount++;
>>> -		chan->desc_pendingcount--;
>>>  		if (chan->desc_submitcount == chan->num_frms)
>>>  			chan->desc_submitcount = 0;
>> "desc_submitcount >= chan->num_frms would be safer here.
> Sure will fix in v2...
>
> Regards,
> Kedar.
>
>>>  	} else {
>> Best regards,
>> Jose Miguel Abreu
>> --
>> To unsubscribe from this list: send the line "unsubscribe dmaengine" in the body
>> of a message to majordomo@vger.kernel.org More majordomo info at
>> http://vger.kernel.org/majordomo-info.html

[toc] | [prev] | [standalone]

Back to top | Article view | linux.kernel

csiph-web