linux-kernel - RE: [PATCH 2/4] dmaengine: vdma: Add support for mulit-channel dma mode

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Message-ID: <C246CAC1457055469EF09E3A7AC4E11A4A5B9B9E@XAP-PVEXMBX01.xlnx.xilinx.com>
Date:	Tue, 28 Jun 2016 05:55:58 +0000
From:	Appana Durga Kedareswara Rao <appana.durga.rao@...inx.com>
To:	Vinod Koul <vinod.koul@...el.com>
CC:	"robh+dt@...nel.org" <robh+dt@...nel.org>,
	"pawel.moll@....com" <pawel.moll@....com>,
	"mark.rutland@....com" <mark.rutland@....com>,
	"ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
	"galak@...eaurora.org" <galak@...eaurora.org>,
	Michal Simek <michals@...inx.com>,
	Soren Brinkmann <sorenb@...inx.com>,
	"dan.j.williams@...el.com" <dan.j.williams@...el.com>,
	"moritz.fischer@...us.com" <moritz.fischer@...us.com>,
	"laurent.pinchart@...asonboard.com" 
	<laurent.pinchart@...asonboard.com>,
	"luis@...ethencourt.com" <luis@...ethencourt.com>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"dmaengine@...r.kernel.org" <dmaengine@...r.kernel.org>
Subject: RE: [PATCH 2/4] dmaengine: vdma: Add support for mulit-channel dma
 mode

Hi Vinod,

	Thanks for the review...

> > > > > >  /**
> > > > > > + * struct xilinx_mcdma_config - DMA Multi channel
> > > > > > +configuration structure
> > > > > > + * @tdest: Channel to operate on
> > > > > > + * @tid:   Channel configuration
> > > > > > + * @tuser: Tuser configuration
> > > > > > + * @ax_user: ax_user value
> > > > > > + * @ax_cache: ax_cache value
> > > > > > + */
> > > > > > +struct xilinx_mcdma_config {
> > > > > > +	u8 tdest;
> > > > > > +	u8 tid;
> > > > > > +	u8 tuser;
> > > > > > +	u8 ax_user;
> > > > > > +	u8 ax_cache;
> > > > >
> > > > > can you describe these in details, what do these do, what are
> > > > > the values to be programmed?
> > > >
> > > > As said above In Multi-Channel Mode each Stream interface can be
> > > > Configured up to 16 channels each channel is differentiated based
> > > > on the tdest
> > > and tid values.
> > >
> > > Then why are you not registering 16 channels for this? That should
> > > give you channel to operate on!
> >
> > The number of channels are configurable.
> > We are registering number of Channels that h/w configured for.
> >
> > Will fix in the next version. Will remove this config.
> > And based on the channel type will configure the h/w.
> 
> Looking at this you should redesign!
> 
> The vchan was designed to operate on 'virtual' channels. The hardware channels
> can be independent of that.
> 
> Your IP seems to be a good fit for that approach. Do not link the two and
> separate them. User can have a virtual channel. In your driver, you can manage
> hardware channels...

Fixed it in the v2 and posted the v2 series.
Please go thought it...

> 
> >
> > >
> > > >
> > > > tdest:
> > > > TDEST provides routing information for the data stream.
> > >
> > > pls elobrate
> >
> > Need to configure this with the channel number that We would like to
> > transfer data.
> 
> This should be internal to driver...

Fixed it in the v2 and posted the v2 series.
Please go thought it...

Regards,
Kedar.

> 
> --
> ~Vinod