linux-kernel - Re: [PATCH v6 2/4] dmaengine: mediatek-cqdma: remove redundant queue structure

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Date:   Thu, 6 Aug 2020 14:27:18 +0800
From:   EastL <EastL.Lee@...iatek.com>
To:     Vinod Koul <vkoul@...nel.org>
CC:     Sean Wang <sean.wang@...iatek.com>, <robh+dt@...nel.org>,
        <mark.rutland@....com>, <matthias.bgg@...il.com>,
        <dmaengine@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <wsd_upstream@...iatek.com>, <cc.hwang@...iatek.com>
Subject: Re: [PATCH v6 2/4] dmaengine: mediatek-cqdma: remove redundant
 queue structure

On Mon, 2020-07-27 at 15:14 +0530, Vinod Koul wrote:
> On 23-07-20, 10:34, EastL wrote:
> > On Wed, 2020-07-15 at 11:49 +0530, Vinod Koul wrote:
> > > On 02-07-20, 15:06, EastL Lee wrote:
> > > 
> > > >  static enum dma_status mtk_cqdma_tx_status(struct dma_chan *c,
> > > >  					   dma_cookie_t cookie,
> > > >  					   struct dma_tx_state *txstate)
> > > >  {
> > > > -	struct mtk_cqdma_vchan *cvc = to_cqdma_vchan(c);
> > > > -	struct mtk_cqdma_vdesc *cvd;
> > > > -	struct virt_dma_desc *vd;
> > > > -	enum dma_status ret;
> > > > -	unsigned long flags;
> > > > -	size_t bytes = 0;
> > > > -
> > > > -	ret = dma_cookie_status(c, cookie, txstate);
> > > > -	if (ret == DMA_COMPLETE || !txstate)
> > > > -		return ret;
> > > > -
> > > > -	spin_lock_irqsave(&cvc->vc.lock, flags);
> > > > -	vd = mtk_cqdma_find_active_desc(c, cookie);
> > > > -	spin_unlock_irqrestore(&cvc->vc.lock, flags);
> > > > -
> > > > -	if (vd) {
> > > > -		cvd = to_cqdma_vdesc(vd);
> > > > -		bytes = cvd->residue;
> > > > -	}
> > > > -
> > > > -	dma_set_residue(txstate, bytes);
> > > 
> > > any reason why you want to remove setting residue?
> > Because Mediatek CQDMA HW can't support residue.
> 
> And previously it did?
No, It was calculated by sw before.
We found that the residue was not necessary, so we removed it.