linux-kernel - Re: [PATCH v2 5/5] ARM: dts: ls1021a-tsn: Use the DSPI controller in poll mode

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Message-ID: <CA+h21hqMVdsUjBdtiHKtKGpyvuaOf25tc4h-GdDEBQqa3EB7tw@mail.gmail.com>
Date:   Tue, 27 Aug 2019 21:16:39 +0300
From:   Vladimir Oltean <olteanv@...il.com>
To:     Mark Brown <broonie@...nel.org>
Cc:     linux-spi@...r.kernel.org, lkml <linux-kernel@...r.kernel.org>,
        devicetree@...r.kernel.org, netdev <netdev@...r.kernel.org>,
        Rob Herring <robh@...nel.org>, Shawn Guo <shawnguo@...nel.org>
Subject: Re: [PATCH v2 5/5] ARM: dts: ls1021a-tsn: Use the DSPI controller in
 poll mode

On Tue, 27 Aug 2019 at 21:13, Mark Brown <broonie@...nel.org> wrote:
>
> On Tue, Aug 27, 2019 at 09:06:14PM +0300, Vladimir Oltean wrote:
> > On Tue, 27 Aug 2019 at 21:05, Mark Brown <broonie@...nel.org> wrote:
> > > On Mon, Aug 26, 2019 at 04:10:51PM +0300, Vladimir Oltean wrote:
>
> > > > I noticed you skipped applying this patch, and I'm not sure that Shawn
> > > > will review it/take it.
> > > > Do you have a better suggestion how I can achieve putting the DSPI
> > > > driver in poll mode for this board? A Kconfig option maybe?
>
> > > DT changes go through the relevant platform trees, not the
> > > subsystem trees, so it's not something I'd expect to apply.
>
> > But at least is it something that you expect to see done through a
> > device tree change?
>
> Well, it's not ideal - if it performs better all the time the
> driver should probably just do it unconditionally.  If there's
> some threashold where it tends to perform better then the driver
> should check for that but IIRC it sounds like the interrupt just
> isn't at all helpful here.

I can't seem to find any situation where it performs worse. Hence my
question on whether it's a better idea to condition this behavior on a
Kconfig option rather than a DT blob which may or may not be in sync.