linux-kernel - Re: [PATCH 03/17] fpga: dfl: fme: support 512bit data width PR

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Date:   Wed, 27 Mar 2019 14:03:34 +0800
From:   Wu Hao <hao.wu@...el.com>
To:     Scott Wood <swood@...hat.com>
Cc:     Alan Tull <atull@...nel.org>, Moritz Fischer <mdf@...nel.org>,
        linux-fpga@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        linux-api@...r.kernel.org, Ananda Ravuri <ananda.ravuri@...el.com>,
        Xu Yilun <yilun.xu@...el.com>
Subject: Re: [PATCH 03/17] fpga: dfl: fme: support 512bit data width PR

On Wed, Mar 27, 2019 at 01:10:31AM -0500, Scott Wood wrote:
> On Wed, 2019-03-27 at 12:37 +0800, Wu Hao wrote:
> > On Tue, Mar 26, 2019 at 04:22:34PM -0500, Scott Wood wrote:
> > > On Tue, 2019-03-26 at 14:33 -0500, Alan Tull wrote:
> > > > On Mon, Mar 25, 2019 at 5:58 PM Scott Wood <swood@...hat.com> wrote:
> > > > > > 
> > > > Hi Scott,
> > > > 
> > > > > On Mon, 2019-03-25 at 17:53 -0500, Scott Wood wrote:
> > > > > > On Mon, 2019-03-25 at 11:07 +0800, Wu Hao wrote:
> > > > > > > +#else
> > > > > > > +static inline void copy512(void *src, void __iomem *dst)
> > > > > > > +{
> > > > > > > +   WARN_ON_ONCE(1);
> > > > > > > +}
> > > > > > > +#endif
> > > > > > 
> Likewise, this will be called if a revision 2 device is used on non-
> > > > > > x86
> > > > > > (or on x86 with an old binutils).  The driver should fall back to
> > > > > > 32-
> > > > > > bit
> > > > > > in such cases.
> > 
> > Unfortunately revision 2 is only for integrated FPGA solution, and it
> > doesn't
> > support any fallback solution (original 32bit data partial reconfiguration
> > is
> > not supported any more), so driver has to WARN in such path.
> 
> >From the commit message it seemed like this was just an optimization, not
> something necessary to support revision 2.
> 
> If there's no way to program the device without AVX512, then printing an
> error message and returning an error to userspace would be better than
> WARN_ON, since it's not actually a kernel bug.

Fair enough. Will do. Thanks for the suggestion.

Hao

> 
> -Scott
>