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

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Date:   Thu, 23 Jul 2020 10:34:10 +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 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.
> 
> > -static void mtk_cqdma_free_active_desc(struct dma_chan *c)
> > +static int mtk_cqdma_terminate_all(struct dma_chan *c)
> >  {
> >  	struct mtk_cqdma_vchan *cvc = to_cqdma_vchan(c);
> > -	bool sync_needed = false;
> > +	struct virt_dma_chan *vc = to_virt_chan(c);
> >  	unsigned long pc_flags;
> >  	unsigned long vc_flags;
> > +	LIST_HEAD(head);
> > +
> > +	/* wait for the VC to be inactive  */
> > +	if (!wait_for_completion_timeout(&cvc->cmp, msecs_to_jiffies(3000)))
> > +		return -EAGAIN;
> >  
> >  	/* acquire PC's lock first due to lock dependency in dma ISR */
> >  	spin_lock_irqsave(&cvc->pc->lock, pc_flags);
> >  	spin_lock_irqsave(&cvc->vc.lock, vc_flags);
> >  
> > -	/* synchronization is required if this VC is active */
> > -	if (mtk_cqdma_is_vchan_active(cvc)) {
> > -		cvc->issue_synchronize = true;
> > -		sync_needed = true;
> > -	}
> > +	/* get VDs from lists */
> > +	vchan_get_all_descriptors(vc, &head);
> > +
> > +	/* free all the VDs */
> > +	vchan_dma_desc_free_list(vc, &head);
> >  
> >  	spin_unlock_irqrestore(&cvc->vc.lock, vc_flags);
> >  	spin_unlock_irqrestore(&cvc->pc->lock, pc_flags);
> 
> Good cleanup, do you need both these locks?
Yes, because we will have multiple vc to pc, it will need both lock.