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

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Date:   Fri, 25 Nov 2016 11:38:51 +0200
From:   Peter Ujfalusi <peter.ujfalusi@...com>
To:     Vinod Koul <vinod.koul@...el.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 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;
}


-- 
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