linux-kernel - Re: [PATCH 7/7] dmaengine: omap-dma: Support for LinkedList transfer of slave

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Date:	Mon, 18 Jul 2016 14:12:51 +0300
From:	Peter Ujfalusi <peter.ujfalusi@...com>
To:	Russell King - ARM Linux <linux@...linux.org.uk>
CC:	<vinod.koul@...el.com>, <linux-kernel@...r.kernel.org>,
	<dmaengine@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>,
	<linux-omap@...r.kernel.org>, <tony@...mide.com>
Subject: Re: [PATCH 7/7] dmaengine: omap-dma: Support for LinkedList transfer
 of slave_sg

On 07/18/16 13:42, Russell King - ARM Linux wrote:
> On Thu, Jul 14, 2016 at 03:42:42PM +0300, Peter Ujfalusi wrote:
>>  struct omap_desc {
>> +	struct omap_chan *c;
>>  	struct virt_dma_desc vd;
> 
> No need for this.  to_omap_dma_chan(foo->vd.tx.chan) will give you the
> omap_chan for the descriptor.  In any case, I question whether you
> actually need this (see below.)

I don't know how I missed that. Works and looks better!


>> +	bool using_ll;
>>  	enum dma_transfer_direction dir;
>>  	dma_addr_t dev_addr;
>>  
>> @@ -81,6 +109,9 @@ struct omap_desc {
>>  };
>>  
>>  enum {
>> +	CAPS_0_SUPPORT_LL123	= BIT(20),	/* Linked List type1/2/3 */
>> +	CAPS_0_SUPPORT_LL4	= BIT(21),	/* Linked List type4 */
>> +
>>  	CCR_FS			= BIT(5),
>>  	CCR_READ_PRIORITY	= BIT(6),
>>  	CCR_ENABLE		= BIT(7),
>> @@ -151,6 +182,19 @@ enum {
>>  	CICR_SUPER_BLOCK_IE	= BIT(14),	/* OMAP2+ only */
>>  
>>  	CLNK_CTRL_ENABLE_LNK	= BIT(15),
>> +
>> +	CDP_DST_VALID_INC	= 0 << 0,
>> +	CDP_DST_VALID_RELOAD	= 1 << 0,
>> +	CDP_DST_VALID_REUSE	= 2 << 0,
>> +	CDP_SRC_VALID_INC	= 0 << 2,
>> +	CDP_SRC_VALID_RELOAD	= 1 << 2,
>> +	CDP_SRC_VALID_REUSE	= 2 << 2,
>> +	CDP_NTYPE_TYPE1		= 1 << 4,
>> +	CDP_NTYPE_TYPE2		= 2 << 4,
>> +	CDP_NTYPE_TYPE3		= 3 << 4,
>> +	CDP_TMODE_NORMAL	= 0 << 8,
>> +	CDP_TMODE_LLIST		= 1 << 8,
>> +	CDP_FAST		= BIT(10),
>>  };
>>  
>>  static const unsigned es_bytes[] = {
>> @@ -180,7 +224,64 @@ static inline struct omap_desc *to_omap_dma_desc(struct dma_async_tx_descriptor
>>  
>>  static void omap_dma_desc_free(struct virt_dma_desc *vd)
>>  {
>> -	kfree(container_of(vd, struct omap_desc, vd));
>> +	struct omap_desc *d = container_of(vd, struct omap_desc, vd);
> 
> 	struct omap_desc *d = to_omap_dma_desc(&vd->tx);
> 
> works just as well, and looks much nicer, and follows the existing code
> pattern.

Yes, I missed this as well.

>> +
>> +	if (d->using_ll) {
>> +		struct omap_chan *c = d->c;
>> +		int i;
>> +
>> +		for (i = 0; i < d->sglen; i++) {
>> +			if (d->sg[i].t2_desc)
>> +				dma_pool_free(c->desc_pool, d->sg[i].t2_desc,
>> +					      d->sg[i].t2_desc_paddr);
> 
> Why do you need a per-channel pool of descriptors?  Won't a per-device
> descriptor pool be much better, and simplify the code here?

I was planning to try per-device pool after this series. I think I went with
per-channel pool as for example bcm2835-dma was doing the same.
In code wise I don't think it is going to simplify much as we still need to
free here what we have allocated. I can test this out.

-- 
Péter