RE: [PATCH -next 3/8] dmaengine: xilinx_dma: Introduce xilinx_dma_get_residue

[Radhey Shyam Pandey <radheys@xilinx.com>]

> -----Original Message-----
> From: Vinod Koul <vkoul@kernel.org>
> Sent: Thursday, September 26, 2019 2:31 AM
> To: Radhey Shyam Pandey <radheys@xilinx.com>
> Cc: dan.j.williams@intel.com; Michal Simek <michals@xilinx.com>;
> nick.graumann@gmail.com; andrea.merello@gmail.com; Appana Durga
> Kedareswara Rao <appanad@xilinx.com>; mcgrof@kernel.org;
> dmaengine@vger.kernel.org; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH -next 3/8] dmaengine: xilinx_dma: Introduce
> xilinx_dma_get_residue
> 
> On 05-09-19, 22:06, Radhey Shyam Pandey wrote:
> > From: Nicholas Graumann <nick.graumann@gmail.com>
> >
> > Introduce a function that can calculate residues for IPs that support it:
> > AXI DMA and CDMA.
> >
> > Signed-off-by: Nicholas Graumann <nick.graumann@gmail.com>
> > Signed-off-by: Radhey Shyam Pandey
> <radhey.shyam.pandey@xilinx.com>
> > ---
> >  drivers/dma/xilinx/xilinx_dma.c | 75
> > ++++++++++++++++++++++++++++++-----------
> >  1 file changed, 56 insertions(+), 19 deletions(-)
> >
> > diff --git a/drivers/dma/xilinx/xilinx_dma.c
> > b/drivers/dma/xilinx/xilinx_dma.c index 9909bfb..4094adb 100644
> > --- a/drivers/dma/xilinx/xilinx_dma.c
> > +++ b/drivers/dma/xilinx/xilinx_dma.c
> > @@ -787,6 +787,51 @@ static void xilinx_dma_free_chan_resources(struct
> > dma_chan *dchan)  }
> >
> >  /**
> > + * xilinx_dma_get_residue - Compute residue for a given descriptor
> > + * @chan: Driver specific dma channel
> > + * @desc: dma transaction descriptor
> > + *
> > + * Return: The number of residue bytes for the descriptor.
> > + */
> > +static u32 xilinx_dma_get_residue(struct xilinx_dma_chan *chan,
> > +				  struct xilinx_dma_tx_descriptor *desc) {
> > +	struct xilinx_cdma_tx_segment *cdma_seg;
> > +	struct xilinx_axidma_tx_segment *axidma_seg;
> > +	struct xilinx_cdma_desc_hw *cdma_hw;
> > +	struct xilinx_axidma_desc_hw *axidma_hw;
> > +	struct list_head *entry;
> > +	u32 residue = 0;
> > +
> > +	/**
> 
> it should be:
>         /*
>          * comment...
> 
Thanks for pointing it out. I will fix it in v2.

> > +	 * VDMA and simple mode do not support residue reporting, so the
> > +	 * residue field will always be 0.
> > +	 */
> > +	if (chan->xdev->dma_config->dmatype == XDMA_TYPE_VDMA ||
> !chan->has_sg)
> > +		return residue;
> 
> why not check this in status callback?
Assuming we mean to move vdma and non-sg check to xilinx_dma_tx_status.
Just a thought- Keeping this check in xilinx_dma_get_residue provides
an abstraction and caller can simply call this func with knowing about
IP config specific residue calculation. Considering this point does it
looks ok ? 
> 
> > +
> > +	list_for_each(entry, &desc->segments) {
> > +		if (chan->xdev->dma_config->dmatype ==
> XDMA_TYPE_CDMA) {
> > +			cdma_seg = list_entry(entry,
> > +					      struct xilinx_cdma_tx_segment,
> > +					      node);
> > +			cdma_hw = &cdma_seg->hw;
> > +			residue += (cdma_hw->control - cdma_hw->status)
> &
> > +				   chan->xdev->max_buffer_len;
> > +		} else {
> > +			axidma_seg = list_entry(entry,
> > +						struct
> xilinx_axidma_tx_segment,
> > +						node);
> > +			axidma_hw = &axidma_seg->hw;
> > +			residue += (axidma_hw->control - axidma_hw-
> >status) &
> > +				   chan->xdev->max_buffer_len;
> > +		}
> > +	}
> > +
> > +	return residue;
> > +}
> > +
> > +/**
> >   * xilinx_dma_chan_handle_cyclic - Cyclic dma callback
> >   * @chan: Driver specific dma channel
> >   * @desc: dma transaction descriptor
> > @@ -995,33 +1040,22 @@ static enum dma_status
> > xilinx_dma_tx_status(struct dma_chan *dchan,  {
> >  	struct xilinx_dma_chan *chan = to_xilinx_chan(dchan);
> >  	struct xilinx_dma_tx_descriptor *desc;
> > -	struct xilinx_axidma_tx_segment *segment;
> > -	struct xilinx_axidma_desc_hw *hw;
> >  	enum dma_status ret;
> >  	unsigned long flags;
> > -	u32 residue = 0;
> >
> >  	ret = dma_cookie_status(dchan, cookie, txstate);
> >  	if (ret == DMA_COMPLETE || !txstate)
> >  		return ret;
> >
> > -	if (chan->xdev->dma_config->dmatype == XDMA_TYPE_AXIDMA) {
> > -		spin_lock_irqsave(&chan->lock, flags);
> > +	spin_lock_irqsave(&chan->lock, flags);
> >
> > -		desc = list_last_entry(&chan->active_list,
> > -				       struct xilinx_dma_tx_descriptor, node);
> > -		if (chan->has_sg) {
> > -			list_for_each_entry(segment, &desc->segments,
> node) {
> > -				hw = &segment->hw;
> > -				residue += (hw->control - hw->status) &
> > -					   chan->xdev->max_buffer_len;
> > -			}
> > -		}
> > -		spin_unlock_irqrestore(&chan->lock, flags);
> > +	desc = list_last_entry(&chan->active_list,
> > +			       struct xilinx_dma_tx_descriptor, node);
> > +	chan->residue = xilinx_dma_get_residue(chan, desc);
> >
> > -		chan->residue = residue;
> > -		dma_set_residue(txstate, chan->residue);
> > -	}
> > +	spin_unlock_irqrestore(&chan->lock, flags);
> > +
> > +	dma_set_residue(txstate, chan->residue);
> >
> >  	return ret;
> >  }
> > @@ -2701,12 +2735,15 @@ static int xilinx_dma_probe(struct
> platform_device *pdev)
> >  					  xilinx_dma_prep_dma_cyclic;
> >  		xdev->common.device_prep_interleaved_dma =
> >  					xilinx_dma_prep_interleaved;
> > -		/* Residue calculation is supported by only AXI DMA */
> > +		/* Residue calculation is supported by only AXI DMA and
> CDMA */
> >  		xdev->common.residue_granularity =
> >
> DMA_RESIDUE_GRANULARITY_SEGMENT;
> >  	} else if (xdev->dma_config->dmatype == XDMA_TYPE_CDMA) {
> >  		dma_cap_set(DMA_MEMCPY, xdev->common.cap_mask);
> >  		xdev->common.device_prep_dma_memcpy =
> xilinx_cdma_prep_memcpy;
> > +		/* Residue calculation is supported by only AXI DMA and
> CDMA */
> > +		xdev->common.residue_granularity =
> > +
> 	DMA_RESIDUE_GRANULARITY_SEGMENT;
> >  	} else {
> >  		xdev->common.device_prep_interleaved_dma =
> >  				xilinx_vdma_dma_prep_interleaved;
> > --
> > 2.7.4
> 
> --
> ~Vinod