RE: [v5 2/6] dmaengine: fsl-qdma: Add qDMA controller driver for Layerscape SoCs

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 




> -----Original Message-----
> From: dmaengine-owner@xxxxxxxxxxxxxxx
> [mailto:dmaengine-owner@xxxxxxxxxxxxxxx] On Behalf Of Wen He
> Sent: 2018年6月11日 16:15
> To: Vinod <vkoul@xxxxxxxxxx>
> Cc: dmaengine@xxxxxxxxxxxxxxx; robh+dt@xxxxxxxxxx;
> devicetree@xxxxxxxxxxxxxxx; Leo Li <leoyang.li@xxxxxxx>; Jiafei Pan
> <jiafei.pan@xxxxxxx>; Jiaheng Fan <jiaheng.fan@xxxxxxx>
> Subject: RE: [v5 2/6] dmaengine: fsl-qdma: Add qDMA controller driver for
> Layerscape SoCs
> 
> 
> 
> > -----Original Message-----
> > From: dmaengine-owner@xxxxxxxxxxxxxxx
> > [mailto:dmaengine-owner@xxxxxxxxxxxxxxx] On Behalf Of Vinod
> > Sent: 2018年6月6日 0:29
> > To: Wen He <wen.he_1@xxxxxxx>
> > Cc: dmaengine@xxxxxxxxxxxxxxx; robh+dt@xxxxxxxxxx;
> > devicetree@xxxxxxxxxxxxxxx; Leo Li <leoyang.li@xxxxxxx>; Jiafei Pan
> > <jiafei.pan@xxxxxxx>; Jiaheng Fan <jiaheng.fan@xxxxxxx>
> > Subject: Re: [v5 2/6] dmaengine: fsl-qdma: Add qDMA controller driver
> > for Layerscape SoCs
> >
> > On 31-05-18, 01:58, Wen He wrote:
> > > > > > > > > +static void fsl_qdma_issue_pending(struct dma_chan *chan) {
> > > > > > > > > +	struct fsl_qdma_chan *fsl_chan =
> to_fsl_qdma_chan(chan);
> > > > > > > > > +	struct fsl_qdma_queue *fsl_queue = fsl_chan->queue;
> > > > > > > > > +	unsigned long flags;
> > > > > > > > > +
> > > > > > > > > +	spin_lock_irqsave(&fsl_queue->queue_lock, flags);
> > > > > > > > > +	spin_lock(&fsl_chan->vchan.lock);
> > > > > > > > > +	if (vchan_issue_pending(&fsl_chan->vchan))
> > > > > > > > > +		fsl_qdma_enqueue_desc(fsl_chan);
> > > > > > > > > +	spin_unlock(&fsl_chan->vchan.lock);
> > > > > > > > > +	spin_unlock_irqrestore(&fsl_queue->queue_lock, flags);
> > > > > > > >
> > > > > > > > why do we need two locks, and since you are doing vchan
> > > > > > > > why should you add your own lock on top
> > > > > > > >
> > > > > > >
> > > > > > > Yes, we need two locks.
> > > > > > > As you know, the QDMA support multiple virtualized blocks
> > > > > > > for multi-core
> > > > > > support.
> > > > > > > so we need to make sure that muliti-core access issues.
> > > > > >
> > > > > > but why cant you use vchan lock for all?
> > > > > >
> > > > >
> > > > > We can't only use vchan lock for all. otherwise enqueue action
> > > > > will be
> > > > interrupted.
> > > >
> > > > I think it is possible to use only vchan lock
> > >
> > > I tried that if I use only vchan lock then qdma will be can't work.
> > > Do you have a other good idea?
> >
> > can you explain the scenario...
> >
> All right.
> When DMA client start transmit, will be call function
> dma_async_issue_pending(), the dma_async_issue_pending() call the hook
> pointer device_issue_pending. The function fsl_qdma_issue_pending() is used
> to fill the device_issue_pending field.
> 
> The function fsl_qdma_issue_pending() call the function
> fsl_qdma_enqueue_desc().
> 
> The function fsl_qdma_enqueue_desc() includes 3 steps.
> 1. peek at the next descriptor to be processed.
> 2. if next descriptor exist, then insert to linked list(used to get it when this
> descriptor transfer complete).
> 3. if next descriptor exist, then writing to qdma.
> 
> In above steps, we will use struct fsl_qdma_chan and struct fsl_qdma_queue,
> so we need two locks to protected it.
> 
> Best Regards,
> Wen
> 

Hi Vinod,

Do you have any other comments besides we discussed?
Can I submit next version patch?

Looking forward to your reply.

Best Regards,
Wen

> > --
> > ~Vinod
> > --
> > To unsubscribe from this list: send the line "unsubscribe dmaengine"
> > in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo
> > info at
> https://emea01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fvger.
> >
> kernel.org%2Fmajordomo-info.html&data=02%7C01%7Cwen.he_1%40nxp.co
> >
> m%7C0f7cc533d6bf4de067d008d5cb01742c%7C686ea1d3bc2b4c6fa92cd99
> >
> c5c301635%7C0%7C0%7C636638129466650321&sdata=zrc0Pf%2Bq0pqixqm
> > LC5jhjLvvV5MiSUM68XtanJxgMbQ%3D&reserved=0
> ㈤旃??迆??瑬+-遍荻w疄藳笔鈓鏵i猷妛豝n噐■?侂h櫒璀?Ⅷ瓽珴
> 閔?(殠娸"濟?m?飦赇z罐枈帼f"穐殘坢
��.n��������+%������w��{.n����z�{��ܨ}���Ơz�j:+v�����w����ޙ��&�)ߡ�a����z�ޗ���ݢj��w�f




[Index of Archives]     [Device Tree Compilter]     [Device Tree Spec]     [Linux Driver Backports]     [Video for Linux]     [Linux USB Devel]     [Linux PCI Devel]     [Linux Audio Users]     [Linux Kernel]     [Linux SCSI]     [XFree86]     [Yosemite Backpacking]


  Powered by Linux