linux-kernel - RE: [PATCH v4 2/3] dmaeninge: xilinx_dma: Fix bug in multiple frame stores scenario in vdma

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Message-ID: <C246CAC1457055469EF09E3A7AC4E11A4A66111B@XAP-PVEXMBX01.xlnx.xilinx.com>
Date:   Fri, 6 Jan 2017 06:01:17 +0000
From:   Appana Durga Kedareswara Rao <appana.durga.rao@...inx.com>
To:     Rob Herring <robh@...nel.org>
CC:     "mark.rutland@....com" <mark.rutland@....com>,
        "dan.j.williams@...el.com" <dan.j.williams@...el.com>,
        "vinod.koul@...el.com" <vinod.koul@...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 v4 2/3] dmaeninge: xilinx_dma: Fix bug in multiple frame
 stores scenario in vdma

Hi Rob,

	Thanks for the review...

 [Snip]
> > -- a/Documentation/devicetree/bindings/dma/xilinx/xilinx_dma.txt
> >> > +++ b/Documentation/devicetree/bindings/dma/xilinx/xilinx_dma.txt
> >> > @@ -66,6 +66,8 @@ Optional child node properties:
> >> >  Optional child node properties for VDMA:
> >> >  - xlnx,genlock-mode: Tells Genlock synchronization is
> >> >     enabled/disabled in hardware.
> >> > +- xlnx,fstore-config: Tells Whether Frame Store Configuration is
> >> > +   enabled/disabled in hardware.
> >>
> >> What's the default (when not present)? That should be the most common
> case.
> >> Looks like the code treats this as bool, but that's not clear here.
> >> The name is not clear what it is doing. Enabling or disabling the feature?
> >
> > Default value is zero...
> > When this property is present it tells hardware is configured for frame store
> configuration.
> 
> So most people will not want "frame store configuration"?

Since the driver is for SoftIP (I mean fpga ip) default h/w configuration of this IP is frame store
Configuration disabled that's in the driver making default value of this configuration as zero.

If users are trying a use case where this configuration should be enabled but in the h/w it is disabled.
In this case driver will warn users to enable this frame store configuration in the h/w.
So that users can enable it in their h/w.

Please let me know if the above expiation is not clear will explain in detail...

> 
> > Will fix the explanation part in the next version like below.
> >  xlnx,fstore-config: Tells hardware is configured for frame store configuration.
> > Is the above explanation clear???
> 
> No, I mean make it obvious from the name of the property:
> xlnx,fstore-config-enable or xlnx,fstore-enable
> 
> And the description needs to say it is boolean.

Sure will fix in the next version...

Regards,
Kedar.

> 
> Rob