linux-kernel - Re: [PATCH v2 2/2] dmaengine: omap-dma: Support for slave devices with data port window

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Date:   Tue, 29 Nov 2016 08:47:14 +0530
From:   Vinod Koul <vinod.koul@...el.com>
To:     Peter Ujfalusi <peter.ujfalusi@...com>
Cc:     dan.j.williams@...el.com, tony@...mide.com, linux@...linux.org.uk,
        dmaengine@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-omap@...r.kernel.org, arnd@...db.de
Subject: Re: [PATCH v2 2/2] dmaengine: omap-dma: Support for slave devices
 with data port window

On Fri, Nov 25, 2016 at 11:38:51AM +0200, Peter Ujfalusi wrote:
> 
> 
> On 11/25/2016 08:12 AM, Vinod Koul wrote:
> > On Thu, Nov 17, 2016 at 02:50:17PM +0200, Peter Ujfalusi wrote:
> >> @@ -921,11 +931,45 @@ static struct dma_async_tx_descriptor *omap_dma_prep_slave_sg(
> >>  
> >>  	d->ccr = c->ccr | CCR_SYNC_FRAME;
> >>  	if (dir == DMA_DEV_TO_MEM) {
> >> -		d->ccr |= CCR_DST_AMODE_POSTINC | CCR_SRC_AMODE_CONSTANT;
> >>  		d->csdp = CSDP_DST_BURST_64 | CSDP_DST_PACKED;
> >> +
> >> +		d->ccr |= CCR_DST_AMODE_POSTINC;
> >> +		if (port_window) {
> >> +			d->ccr |= CCR_SRC_AMODE_DBLIDX;
> >> +			d->ei = 1;
> >> +			/*
> >> +			 * One frame covers the port_window and by  configure
> >> +			 * the source frame index to be -1 * (port_window - 1)
> >> +			 * we instruct the sDMA that after a frame is processed
> >> +			 * it should move back to the start of the window.
> >> +			 */
> >> +			d->fi = -(port_window - 1);
> >> +
> >> +			if (port_window >= 64)
> >> +				d->csdp = CSDP_SRC_BURST_64 | CSDP_SRC_PACKED;
> >> +			else if (port_window >= 32)
> >> +				d->csdp = CSDP_SRC_BURST_32 | CSDP_SRC_PACKED;
> >> +			else if (port_window >= 16)
> >> +				d->csdp = CSDP_SRC_BURST_16 | CSDP_SRC_PACKED;
> > 
> > this and other would look better with a switch..
> 
> I'm not sure if it will be any better:
> 
> switch (port_window) {
> case 0 ... 15:
> 	break;
> case 16 ... 31:
> 	d->csdp = CSDP_SRC_BURST_16 | CSDP_SRC_PACKED;
> 	break;
> case 32 ... 63:
> 	d->csdp = CSDP_SRC_BURST_32 | CSDP_SRC_PACKED;
> 	break;
> default:
> 	d->csdp = CSDP_SRC_BURST_64 | CSDP_SRC_PACKED;
> 	break;
> }

Yeah agree with you on this..

-- 
~Vinod