linux-kernel - RE: [PATCH 2/2] fpga: Add support for Xilinx DFX AXI Shutdown manager

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Date:   Wed, 27 Jan 2021 08:46:15 +0000
From:   Nava kishore Manne <navam@...inx.com>
To:     Moritz Fischer <mdf@...nel.org>
CC:     "trix@...hat.com" <trix@...hat.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        Michal Simek <michals@...inx.com>,
        "linux-fpga@...r.kernel.org" <linux-fpga@...r.kernel.org>,
        "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>,
        git <git@...inx.com>,
        "chinnikishore369@...il.com" <chinnikishore369@...il.com>
Subject: RE: [PATCH 2/2] fpga: Add support for Xilinx DFX AXI Shutdown manager

Hi Moritz,

	Please find my response inline.

> -----Original Message-----
> From: Moritz Fischer <mdf@...nel.org>
> Sent: Friday, January 22, 2021 10:45 AM
> To: Nava kishore Manne <navam@...inx.com>
> Cc: Moritz Fischer <mdf@...nel.org>; trix@...hat.com;
> robh+dt@...nel.org; Michal Simek <michals@...inx.com>; linux-
> fpga@...r.kernel.org; devicetree@...r.kernel.org; linux-arm-
> kernel@...ts.infradead.org; linux-kernel@...r.kernel.org; git
> <git@...inx.com>; chinnikishore369@...il.com
> Subject: Re: [PATCH 2/2] fpga: Add support for Xilinx DFX AXI Shutdown
> manager
> 
> On Tue, Jan 19, 2021 at 06:34:54AM +0000, Nava kishore Manne wrote:
> > Hi Moritz,
> >
> > 	Thanks for the review.
> > Please find my response inline.
> >
> > > -----Original Message-----
> > > From: Moritz Fischer <mdf@...nel.org>
> > > Sent: Saturday, January 16, 2021 8:28 AM
> > > To: Nava kishore Manne <navam@...inx.com>
> > > Cc: mdf@...nel.org; trix@...hat.com; robh+dt@...nel.org; Michal
> > > Simek <michals@...inx.com>; linux-fpga@...r.kernel.org;
> > > devicetree@...r.kernel.org; linux-arm-kernel@...ts.infradead.org;
> > > linux- kernel@...r.kernel.org; git <git@...inx.com>;
> > > chinnikishore369@...il.com
> > > Subject: Re: [PATCH 2/2] fpga: Add support for Xilinx DFX AXI
> > > Shutdown manager
> > >
> > > Hi,
> > >
> > > On Fri, Jan 15, 2021 at 07:04:31AM +0530, Nava kishore Manne wrote:
> > > > This patch adds support for Xilinx Dynamic Function eXchange(DFX)
> > > > AXI shutdown manager IP. It can be used to safely handling the AXI
> > > > traffic on a Reconfigurable Partition when it is undergoing
> > > > dynamic reconfiguration and there by preventing system deadlock
> > > > that may occur if AXI transactions are interrupted during
> reconfiguration.
> > > >
> > > > PR-Decoupler and AXI shutdown manager are completely different IPs.
> > > > But both the IP registers are compatible and also both belong to
> > > > the same sub-system (fpga-bridge).So using same driver for both IP's.
> > >
> > > I'm a bit confused, the whole goal here is to give the thing a different
> name?
> >
> >
> > Both the PR Decoupler and AXI Shutdown IP manager IP's are follows same
> register spec.
> > Most of the code is common so we thought of reusing  same driver for AXI
> shutdown manager as well.
> 
> What are the differences, though other than it shows a different name?

The PR-Decoupler And Axi Shut down manager are different IP's 

PR-Decoupler IP can be used to make the interface between a Reconfigurable Partition
and the static logic safe while Partial Reconfiguration is occurring. When active,
user-selected signals crossing between the Reconfigurable Partition and the static logic
are driven to user configurable values. When inactive, signals are passed unaltered.

Coming to the Axi Shutdown manager IP it's safely handles AXI4MM and AXI4-Lite interfaces
on a Reconfigurable Partition when it is undergoing dynamic reconfiguration (DFX),
preventing system deadlock that can occur if AXI transactions are interrupted by DFX.

For more details please refer the below links:
https://www.xilinx.com/support/documentation/ip_documentation/pr_decoupler/v1_0/pg227-pr-decoupler.pdf 
https://www.xilinx.com/support/documentation/ip_documentation/dfx_axi_shutdown_manager/v1_0/pg377-dfx-axi-shutdown-manager.pdf  

Both the IP functionality's are different but the IP's registers spec is same and also they fall under
the same bridge drivers category and most of the code is common except the naming conventions.
So we thought of using the same driver for both the IP's with different naming conventions.

Regards,
Navakishore.