RE: [PATCHv10 2/2] dma: Add Freescale eDMA engine driver support

[Jingchang Lu]

> -----Original Message-----
> From: Vinod Koul [mailto:vinod.koul@xxxxxxxxx]
> Sent: Monday, January 20, 2014 3:40 PM
> To: Lu Jingchang-B35083
> Cc: dan.j.williams@xxxxxxxxx; arnd@xxxxxxxx; shawn.guo@xxxxxxxxxx;
> pawel.moll@xxxxxxx; mark.rutland@xxxxxxx; swarren@xxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> devicetree@xxxxxxxxxxxxxxx; Wang Huan-B18965
> Subject: Re: [PATCHv10 2/2] dma: Add Freescale eDMA engine driver support
> 
> On Fri, Jan 17, 2014 at 02:04:44PM +0800, Jingchang Lu wrote:
> > Add Freescale enhanced direct memory(eDMA) controller support.
> > This module can be found on Vybrid and LS-1 SoCs.
> >
> > Signed-off-by: Alison Wang <b18965@xxxxxxxxxxxxx>
> > Signed-off-by: Jingchang Lu <b35083@xxxxxxxxxxxxx>
> > Acked-by: Arnd Bergmann <arnd@xxxxxxxx>
> > ---
> 
> > +static int fsl_edma_control(struct dma_chan *chan, enum dma_ctrl_cmd
> cmd,
> > +		unsigned long arg)
> > +{
> > +	struct fsl_edma_chan *fsl_chan = to_fsl_edma_chan(chan);
> > +	struct dma_slave_config *cfg = (void *)arg;
> > +	unsigned long flags;
> > +	LIST_HEAD(head);
> > +
> > +	switch (cmd) {
> > +	case DMA_TERMINATE_ALL:
> > +		spin_lock_irqsave(&fsl_chan->vchan.lock, flags);
> > +		fsl_edma_disable_request(fsl_chan);
> > +		fsl_chan->edesc = NULL;
> > +		vchan_get_all_descriptors(&fsl_chan->vchan, &head);
> > +		spin_unlock_irqrestore(&fsl_chan->vchan.lock, flags);
> > +		vchan_dma_desc_free_list(&fsl_chan->vchan, &head);
> > +		return 0;
> well what happens to the current ongoing transactions, i don't see those
> getting
> terminated?
The fsl_edma_disable_request(fsl_chan) would end the channel's ongoing transaction, then
the eDMA would not response to device dma request, and the vchan_dma_desc_free_list()
will release all associate memory. Thanks.

> 
> > +
> > +	case DMA_SLAVE_CONFIG:
> > +		fsl_chan->fsc.dir = cfg->direction;
> > +		if (cfg->direction == DMA_DEV_TO_MEM) {
> > +			fsl_chan->fsc.dev_addr = cfg->src_addr;
> > +			fsl_chan->fsc.addr_width = cfg->src_addr_width;
> > +			fsl_chan->fsc.burst = cfg->src_maxburst;
> > +			fsl_chan->fsc.attr = fsl_edma_get_tcd_attr(cfg-
> >src_addr_width);
> > +		} else if (cfg->direction == DMA_MEM_TO_DEV) {
> > +			fsl_chan->fsc.dev_addr = cfg->dst_addr;
> > +			fsl_chan->fsc.addr_width = cfg->dst_addr_width;
> > +			fsl_chan->fsc.burst = cfg->dst_maxburst;
> > +			fsl_chan->fsc.attr = fsl_edma_get_tcd_attr(cfg-
> >dst_addr_width);
> okay atrr is address width, why not save this standard struct instead?
The value saved in fsc.attr is transferred by fsl_edma_get_tcd_attr(), it can
be set into the channel control register later directly. the edma driver doesn't
need to save all dma_slave_config parameters, so it only gets the necessaries.
Thanks.
 
> 
> > +		} else {
> > +			return -EINVAL;
> > +		}
> > +		return 0;
> > +
> > +	case DMA_PAUSE:
> > +		spin_lock_irqsave(&fsl_chan->vchan.lock, flags);
> > +		if (fsl_chan->edesc) {
> > +			fsl_edma_disable_request(fsl_chan);
> > +			fsl_chan->status = DMA_PAUSED;
> > +		}
> > +		spin_unlock_irqrestore(&fsl_chan->vchan.lock, flags);
> > +		return 0;
> > +
> > +	case DMA_RESUME:
> > +		spin_lock_irqsave(&fsl_chan->vchan.lock, flags);
> > +		if (fsl_chan->edesc) {
> > +			fsl_edma_enable_request(fsl_chan);
> > +			fsl_chan->status = DMA_IN_PROGRESS;
> > +		}
> > +		spin_unlock_irqrestore(&fsl_chan->vchan.lock, flags);
> > +		return 0;
> > +
> > +	default:
> > +		return -ENXIO;
> > +	}
> > +}
> > +
> 
> > +static struct fsl_edma_desc *fsl_edma_alloc_desc(struct fsl_edma_chan
> *fsl_chan,
> > +		int sg_len)
> > +{
> > +	struct fsl_edma_desc *fsl_desc;
> > +	int i;
> > +
> > +	fsl_desc = kzalloc(sizeof(*fsl_desc) + sizeof(struct
> fsl_edma_sw_tcd) * sg_len,
> > +				GFP_NOWAIT);
> > +	if (!fsl_desc)
> > +		return NULL;
> > +
> > +	fsl_desc->echan = fsl_chan;
> > +	fsl_desc->n_tcds = sg_len;
> > +	for (i = 0; i < sg_len; i++) {
> > +		fsl_desc->tcd[i].vtcd = dma_pool_alloc(fsl_chan->tcd_pool,
> > +					GFP_NOWAIT, &fsl_desc->tcd[i].ptcd);
> > +		if (!fsl_desc->tcd[i].vtcd)
> > +			goto err;
> > +	}
> > +	return fsl_desc;
> > +
> > +err:
> > +	while (--i >= 0)
> > +		dma_pool_free(fsl_chan->tcd_pool, fsl_desc->tcd[i].vtcd,
> > +				fsl_desc->tcd[i].ptcd);
> > +	kfree(fsl_desc);
> > +	return NULL;
> > +}
> > +
> > +static struct dma_async_tx_descriptor *fsl_edma_prep_dma_cyclic(
> > +		struct dma_chan *chan, dma_addr_t dma_addr, size_t buf_len,
> > +		size_t period_len, enum dma_transfer_direction direction,
> > +		unsigned long flags, void *context)
> > +{
> you may want to implement the capablities api subsequently for audio
> usage.
Do you mean the device_slave_caps function? If it is, I will add it.
Thanks.

> 
> > +	struct fsl_edma_chan *fsl_chan = to_fsl_edma_chan(chan);
> > +	struct fsl_edma_desc *fsl_desc;
> > +	dma_addr_t dma_buf_next;
> > +	int sg_len, i;
> > +	u32 src_addr, dst_addr, last_sg, nbytes;
> > +	u16 soff, doff, iter;
> > +
> > +	if (!is_slave_direction(fsl_chan->fsc.dir))
> > +		return NULL;
> > +
> > +	sg_len = buf_len / period_len;
> > +	fsl_desc = fsl_edma_alloc_desc(fsl_chan, sg_len);
> > +	if (!fsl_desc)
> > +		return NULL;
> > +	fsl_desc->iscyclic = true;
> > +
> > +	dma_buf_next = dma_addr;
> > +	nbytes = fsl_chan->fsc.addr_width * fsl_chan->fsc.burst;
> > +	iter = period_len / nbytes;
> empty line here pls
Ok, thanks.


Best Regards,
Jingchang
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