Re: [PATCH 1/2] dma: pl330: improve pl330_tx_status() function

["Krzysztof Kozłowski" <k.kozlowski@samsung.com>]

On 25.11.2014 13:25, Robert Baldyga wrote:
> This patch adds possibility to read residue of DMA transfer. It's useful
> when we want to know how many bytes have been transfered before we
> terminate channel. It can take place, for example, on timeout interrupt.
> 
> Signed-off-by: Lukasz Czerwinski <l.czerwinski@samsung.com>
> Signed-off-by: Robert Baldyga <r.baldyga@samsung.com>
> ---
>  drivers/dma/pl330.c | 61 ++++++++++++++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 60 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
> index d5149aa..c32806d 100644
> --- a/drivers/dma/pl330.c
> +++ b/drivers/dma/pl330.c
> @@ -437,6 +437,7 @@ struct dma_pl330_chan {
>  	/* For D-to-M and M-to-D channels */
>  	int burst_sz; /* the peripheral fifo width */
>  	int burst_len; /* the number of burst */
> +	int transfered;
>  	dma_addr_t fifo_addr;
>  
>  	/* for cyclic capability */
> @@ -500,6 +501,9 @@ struct dma_pl330_desc {
>  
>  	enum desc_status status;
>  
> +	int bytes_requested;
> +	int direction;
> +
>  	/* The channel which currently holds this desc */
>  	struct dma_pl330_chan *pchan;
>  
> @@ -2156,11 +2160,60 @@ static void pl330_free_chan_resources(struct dma_chan *chan)
>  	spin_unlock_irqrestore(&pch->lock, flags);
>  }
>  
> +int pl330_get_current_xferred_count(struct dma_pl330_chan *pch,
> +		struct dma_pl330_desc *desc)
> +{
> +	u32 val, addr;
> +	struct pl330_thread *thrd = pch->thread;
> +	void __iomem *regs = thrd->dmac->base;
> +
> +	val = addr = 0;
> +	switch (desc->direction) {
> +	case DMA_MEM_TO_DEV:
> +		val = readl(regs + SA(thrd->id));
> +		addr = desc->px.src_addr;
> +		break;
> +	case DMA_DEV_TO_MEM:
> +		val = readl(regs + DA(thrd->id));
> +		addr = desc->px.dst_addr;
> +		break;
> +	default:
> +		break;
> +	}
> +	return val - addr;
> +}
> +
>  static enum dma_status
>  pl330_tx_status(struct dma_chan *chan, dma_cookie_t cookie,
>  		 struct dma_tx_state *txstate)
>  {
> -	return dma_cookie_status(chan, cookie, txstate);
> +	enum dma_status ret;
> +	unsigned long flags;
> +	struct dma_pl330_desc *desc;
> +	struct dma_pl330_chan *pch = to_pchan(chan);
> +	unsigned int bytes_transferred;
> +	unsigned int residual;
> +
> +	/* Check in pending list */
> +	spin_lock_irqsave(&pch->lock, flags);
> +	list_for_each_entry(desc, &pch->work_list, node) {
> +		if (desc->txd.cookie == cookie) {
> +			bytes_transferred =
> +				pl330_get_current_xferred_count(pch, desc);

As in 2nd patch - what if this get called after all transfers complete?
You're touching the device here so pm_runtime_get_sync()/put/autosuspend
may be needed.

Best regards,
Krzysztof

> +			residual =  desc->bytes_requested -
> +				bytes_transferred % desc->bytes_requested;
> +			dma_set_residue(txstate, residual);
> +			ret = desc->status;
> +			spin_unlock_irqrestore(&pch->lock, flags);
> +			return ret;
> +		}
> +	}
> +	spin_unlock_irqrestore(&pch->lock, flags);
> +
> +	ret = dma_cookie_status(chan, cookie, txstate);
> +	dma_set_residue(txstate,  pch->transfered);
> +
> +	return ret;
>  }
>  
>  static void pl330_issue_pending(struct dma_chan *chan)
> @@ -2421,10 +2474,13 @@ static struct dma_async_tx_descriptor *pl330_prep_dma_cyclic(
>  			break;
>  		}
>  
> +		desc->direction = direction;
>  		desc->rqtype = direction;
>  		desc->rqcfg.brst_size = pch->burst_sz;
>  		desc->rqcfg.brst_len = 1;
> +		desc->bytes_requested = period_len;
>  		fill_px(&desc->px, dst, src, period_len);
> +		pch->transfered = 0;
>  
>  		if (!first)
>  			first = desc;
> @@ -2554,9 +2610,12 @@ pl330_prep_slave_sg(struct dma_chan *chan, struct scatterlist *sgl,
>  				sg_dma_address(sg), addr, sg_dma_len(sg));
>  		}
>  
> +		desc->direction = direction;
>  		desc->rqcfg.brst_size = pch->burst_sz;
>  		desc->rqcfg.brst_len = 1;
>  		desc->rqtype = direction;
> +		desc->bytes_requested = sg_dma_len(sg);
> +		pch->transfered = 0;
>  	}
>  
>  	/* Return the last desc in the chain */
>