Re: [PATCH v4 3/3] dmaengine: ti: edma: Support for polled (memcpy) completion

[Vinod Koul <vkoul@kernel.org>]

On 18-06-19, 16:21, Peter Ujfalusi wrote:
> When a DMA client driver does not set the DMA_PREP_INTERRUPT because it
> does not want to use interrupts for DMA completion or because it can not
> rely on DMA interrupts due to executing the memcpy when interrupts are
> disabled it will poll the status of the transfer.
> 
> Since we can not tell from any EDMA register that the transfer is
> completed, we can only know that the paRAM set has been sent to TPTC for
> processing we need to check the residue of the transfer, if it is 0 then
> the transfer is completed.
> 
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
> ---
>  drivers/dma/ti/edma.c | 37 +++++++++++++++++++++++++++++++++----
>  1 file changed, 33 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/dma/ti/edma.c b/drivers/dma/ti/edma.c
> index 48b155cab822..87d7fdaa204b 100644
> --- a/drivers/dma/ti/edma.c
> +++ b/drivers/dma/ti/edma.c
> @@ -171,6 +171,7 @@ struct edma_desc {
>  	struct list_head		node;
>  	enum dma_transfer_direction	direction;
>  	int				cyclic;
> +	bool				polled;
>  	int				absync;
>  	int				pset_nr;
>  	struct edma_chan		*echan;
> @@ -1240,8 +1241,9 @@ static struct dma_async_tx_descriptor *edma_prep_dma_memcpy(
>  
>  	edesc->pset[0].param.opt |= ITCCHEN;
>  	if (nslots == 1) {
> -		/* Enable transfer complete interrupt */
> -		edesc->pset[0].param.opt |= TCINTEN;
> +		/* Enable transfer complete interrupt if requested */
> +		if (tx_flags & DMA_PREP_INTERRUPT)
> +			edesc->pset[0].param.opt |= TCINTEN;
>  	} else {
>  		/* Enable transfer complete chaining for the first slot */
>  		edesc->pset[0].param.opt |= TCCHEN;
> @@ -1268,9 +1270,14 @@ static struct dma_async_tx_descriptor *edma_prep_dma_memcpy(
>  		}
>  
>  		edesc->pset[1].param.opt |= ITCCHEN;
> -		edesc->pset[1].param.opt |= TCINTEN;
> +		/* Enable transfer complete interrupt if requested */
> +		if (tx_flags & DMA_PREP_INTERRUPT)
> +			edesc->pset[1].param.opt |= TCINTEN;
>  	}
>  
> +	if (!(tx_flags & DMA_PREP_INTERRUPT))
> +		edesc->polled = true;
> +
>  	return vchan_tx_prep(&echan->vchan, &edesc->vdesc, tx_flags);
>  }
>  
> @@ -1840,18 +1847,40 @@ static enum dma_status edma_tx_status(struct dma_chan *chan,
>  {
>  	struct edma_chan *echan = to_edma_chan(chan);
>  	struct virt_dma_desc *vdesc;
> +	struct dma_tx_state txstate_tmp;
>  	enum dma_status ret;
>  	unsigned long flags;
>  
>  	ret = dma_cookie_status(chan, cookie, txstate);
> -	if (ret == DMA_COMPLETE || !txstate)
> +
> +	/* Provide a dummy dma_tx_state for completion checking */
> +	if (ret != DMA_COMPLETE && !txstate)
> +		txstate = &txstate_tmp;
> +
> +	if (ret == DMA_COMPLETE)
>  		return ret;

why not do:

        if (ret == DMA_COMPLETE)
                return ret;

        if (!txstate)
                txstate = &txstate_tmp;

> +	txstate->residue = 0;
>  	spin_lock_irqsave(&echan->vchan.lock, flags);
>  	if (echan->edesc && echan->edesc->vdesc.tx.cookie == cookie)
>  		txstate->residue = edma_residue(echan->edesc);
>  	else if ((vdesc = vchan_find_desc(&echan->vchan, cookie)))
>  		txstate->residue = to_edma_desc(&vdesc->tx)->residue;
> +
> +	/*
> +	 * Mark the cookie completed if the residue is 0 for non cyclic
> +	 * transfers
> +	 */
> +	if (ret != DMA_COMPLETE && !txstate->residue &&
> +	    echan->edesc && echan->edesc->polled &&
> +	    echan->edesc->vdesc.tx.cookie == cookie) {
> +		edma_stop(echan);
> +		vchan_cookie_complete(&echan->edesc->vdesc);
> +		echan->edesc = NULL;
> +		edma_execute(echan);
> +		ret = DMA_COMPLETE;
> +	}
> +
>  	spin_unlock_irqrestore(&echan->vchan.lock, flags);
>  
>  	return ret;
> -- 
> Peter
> 
> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki

-- 
~Vinod

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