netdev - RE: Re: [PATCH net-next 1/4] ixgbe: sparc: rename the ARCH_WANT_RELAX_ORDER to IXGBE_ALLOW_RELAXED

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Date:   Thu, 13 Apr 2017 09:10:32 +0000
From:   Gabriele Paoloni <gabriele.paoloni@...wei.com>
To:     "davem@...emloft.net" <davem@...emloft.net>
CC:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        Robin Murphy <Robin.Murphy@....com>,
        "jeffrey.t.kirsher@...el.com" <jeffrey.t.kirsher@...el.com>,
        "alexander.duyck@...il.com" <alexander.duyck@...il.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Dingtianhong <dingtianhong@...wei.com>,
        Linuxarm <linuxarm@...wei.com>
Subject: RE: Re: [PATCH net-next 1/4] ixgbe: sparc: rename the
 ARCH_WANT_RELAX_ORDER to IXGBE_ALLOW_RELAXED_ORDER

Hi David

> -----Original Message-----
> Subject: Re: [PATCH net-next 1/4] ixgbe: sparc: rename the
> ARCH_WANT_RELAX_ORDER to IXGBE_ALLOW_RELAXED_ORDER
> Date: Sat, 1 Apr 2017 11:26:03 -0700
> From: David Miller <davem@...emloft.net>
> To: dingtianhong@...wei.com
> CC: catalin.marinas@....com, will.deacon@....com, mark.rutland@....com,
> robin.murphy@....com, jeffrey.t.kirsher@...el.com,
> alexander.duyck@...il.com, linux-arm-kernel@...ts.infradead.org,
> netdev@...r.kernel.org
> 
> From: Ding Tianhong <dingtianhong@...wei.com>
> Date: Sat, 1 Apr 2017 15:25:51 +0800
> 
> > Till now only the Intel ixgbe could support enable
> > Relaxed ordering in the drivers for special architecture,
> > but the ARCH_WANT_RELAX_ORDER is looks like a general name
> > for all arch, so rename to a specific name for intel
> > card looks more appropriate.
> >
> > Signed-off-by: Ding Tianhong <dingtianhong@...wei.com>
> 
> This is not a driver specific facility.
> 
> Any driver can test this symbol and act accordingly.
> 
> Just because IXGBE is the first and only user, doesn't mean
> the facility is driver specific.


Please correct me if I am wrong but my understanding is that the standard
way to enable/disable relaxed ordering is to set/clear bit 4 of the Device
Control Register (PCI_EXP_DEVCTL_RELAX_EN 0x0010 /* Enable relaxed
ordering */).
Now I have looked up for all drivers either enabling or disabling relaxed
ordering and none of them seems to need a symbol to decide whether to
enable it or not.
Also it seems to me enabling/disabling relaxed ordering is never bound to the
host architecture.

So why this should be (or it is expected to be) a generic symbol?
Wouldn't it be more correct to have this as a driver specific symbol now and
move it to a generic one later once we have other drivers requiring it?
  
Many thanks
Gab

> 
> Thank you.
> 
> .
>