linux-kernel - Re: [PATCH v5 1/3] dmaengine: xilinx_dma: Check for channel idle state before submitting dma descriptor

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Date:   Fri, 13 Jan 2017 10:59:39 +0530
From:   Vinod Koul <vinod.koul@...el.com>
To:     Appana Durga Kedareswara Rao <appana.durga.rao@...inx.com>
Cc:     "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "michal.simek@...inx.com" <michal.simek@...inx.com>,
        Soren Brinkmann <sorenb@...inx.com>,
        "moritz.fischer@...us.com" <moritz.fischer@...us.com>,
        "laurent.pinchart@...asonboard.com" 
        <laurent.pinchart@...asonboard.com>,
        "luis@...ethencourt.com" <luis@...ethencourt.com>,
        "Jose.Abreu@...opsys.com" <Jose.Abreu@...opsys.com>,
        "dmaengine@...r.kernel.org" <dmaengine@...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>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH v5 1/3] dmaengine: xilinx_dma: Check for channel idle
 state before submitting dma descriptor

On Fri, Jan 13, 2017 at 04:28:11AM +0000, Appana Durga Kedareswara Rao wrote:
> Hi Vinod,
> 
> 	Thanks for the review...
> > 
> > On Sat, Jan 07, 2017 at 12:15:28PM +0530, Kedareswara rao Appana wrote:
> > > Add channel idle state to ensure that dma descriptor is not
> > > submitted when VDMA engine is in progress.
> > 
> > any reason why you want to make your own varible and not use the HW to
> > query
> > as done earlier. It is not clear to me why that is removed from description
> 
> We need to poll for a bit in the status register to know the dma state.
> We are currently doing that in the driver hot path
> To avoid this using own variables.

It would be worthwhile to document these, down the line people may not
remeber the motivation


-- 
~Vinod