RE: [PATCH V4 03/14] DMA: PL330: Support DMA_SLAVE_CONFIG command

[Boojin Kim <boojin.kim@samsung.com>]

Vinod Koul Wrote:
> Sent: Monday, July 25, 2011 10:48 PM
> To: Boojin Kim
> Cc: vinod.koul@intel.com; linux-arm-kernel@lists.infradead.org; linux-
> samsung-soc@vger.kernel.org; 'Kukjin Kim'; 'Jassi Brar'; 'Grant
> Likely'; 'Mark Brown'; 'Dan Williams'
> Subject: RE: [PATCH V4 03/14] DMA: PL330: Support DMA_SLAVE_CONFIG
> command
>
> On Mon, 2011-07-25 at 21:51 +0900, Boojin Kim wrote:
> > Vinod Koul Wrote:
> > > Sent: Monday, July 25, 2011 7:27 PM
> > > To: Boojin Kim
> > > Cc: vinod.koul@intel.com; linux-arm-kernel@lists.infradead.org;
> linux-
> > > samsung-soc@vger.kernel.org; Kukjin Kim; Jassi Brar; Grant Likely;
> > > Mark Brown; Dan Williams
> > > Subject: Re: [PATCH V4 03/14] DMA: PL330: Support DMA_SLAVE_CONFIG
> > > command
> > >
> > > On Mon, 2011-07-25 at 10:28 +0900, Boojin Kim wrote:
> > > > This patch adds support DMA_SLAVE_CONFIG command.
> > > >
> > > > Signed-off-by: Boojin Kim <boojin.kim@samsung.com>
> > > > ---
> > > >  drivers/dma/pl330.c |   53
> +++++++++++++++++++++++++++++++++++++----
> > > ---------
> > > >  1 files changed, 39 insertions(+), 14 deletions(-)
> > > >
> > > > diff --git a/drivers/dma/pl330.c b/drivers/dma/pl330.c
> > > > index 586ab39..880f010 100644
> > > > --- a/drivers/dma/pl330.c
> > > > +++ b/drivers/dma/pl330.c
> > > > @@ -256,25 +256,50 @@ static int
> pl330_alloc_chan_resources(struct
> > > dma_chan *chan)
> > > >  static int pl330_control(struct dma_chan *chan, enum
> dma_ctrl_cmd
> > > cmd, unsigned long arg)
> > > >  {
> > > >  	struct dma_pl330_chan *pch = to_pchan(chan);
> > > > -	struct dma_pl330_desc *desc;
> > > > +	struct dma_pl330_desc *desc, *_dt;
> > > >  	unsigned long flags;
> > > > +	struct dma_pl330_dmac *pdmac = pch->dmac;
> > > > +	struct dma_slave_config *slave_config;
> > > > +	struct dma_pl330_peri *peri;
> > > > +	LIST_HEAD(list);
> > > >
> > > > -	/* Only supports DMA_TERMINATE_ALL */
> > > > -	if (cmd != DMA_TERMINATE_ALL)
> > > > -		return -ENXIO;
> > > > -
> > > > -	spin_lock_irqsave(&pch->lock, flags);
> > > > -
> > > > -	/* FLUSH the PL330 Channel thread */
> > > > -	pl330_chan_ctrl(pch->pl330_chid, PL330_OP_FLUSH);
> > > > +	switch (cmd) {
> > > > +	case DMA_TERMINATE_ALL:
> > > > +		spin_lock_irqsave(&pch->lock, flags);
> > > >
> > > > -	/* Mark all desc done */
> > > > -	list_for_each_entry(desc, &pch->work_list, node)
> > > > -		desc->status = DONE;
> > > > +		/* FLUSH the PL330 Channel thread */
> > > > +		pl330_chan_ctrl(pch->pl330_chid, PL330_OP_FLUSH);
> > > >
> > > > -	spin_unlock_irqrestore(&pch->lock, flags);
> > > > +		/* Mark all desc done */
> > > > +		list_for_each_entry_safe(desc, _dt, &pch-
> >work_list , node)
> > > {
> > > > +			desc->status = DONE;
> > > > +			pch->completed = desc->txd.cookie;
> > > > +			list_move_tail(&desc->node, &list);
> > > > +		}
> > > >
> > > > -	pl330_tasklet((unsigned long) pch);
> > > > +		list_splice_tail_init(&list, &pdmac->desc_pool);
> > > > +		spin_unlock_irqrestore(&pch->lock, flags);
> > > > +		break;
> > > > +	case DMA_SLAVE_CONFIG:
> > > > +		slave_config = (struct dma_slave_config *)arg;
> > > > +		peri = pch->chan.private;
> > > > +
> > > > +		if (slave_config->direction == DMA_TO_DEVICE) {
> > > > +			if (slave_config->dst_addr)
> > > > +				peri->fifo_addr = slave_config-
> >dst_addr;
> > > > +			if (slave_config->dst_addr_width)
> > > > +				peri->burst_sz = __ffs(slave_config-
> > > >dst_addr_width);
> > > This doesn't sound right, why can't you use xxx_maxburst field
> instead?
> > Can you explain the problem in more detail?
> > Do you mean that 'xxx_maxburst' takes place of 'xxx_addr_width' or
> __ffs()
> > isn't proper here?
> >
> > Additionally, I will modify this code to consider '_maxburst' field.
> __ffs is okay and sensible.
> I meant you should use proper fields for passing info, which in this
> case would be dst_maxburst for specifying destination burst sizes
I think the naming seems to make confusion.
'Peri->burst_sz' on this code means the width of fifo in bytes of the peri. 
It's same with the meaning 'xxx_addr_width'. So, I think it's proper usage.
'peri->burst_sz' is passed to PL330 HW. PL330 HW wants to get the power of 2 
based the fifo width for it.
For example, If fifo width is 8 bytes, PL330 HW should get '3' for it.
And I will modify code to consider xxx_maxburst.


> --
> ~Vinod Koul
> Intel Corp.