linux-kernel - Re: [RFC PATCH v2 07/12] mtd: rawnand: ams-delta: Set port direction once per transfer

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Date:   Wed, 08 Aug 2018 18:55:35 +0200
From:   Janusz Krzysztofik <jmkrzyszt@...il.com>
To:     Boris Brezillon <boris.brezillon@...tlin.com>
Cc:     Linus Walleij <linus.walleij@...aro.org>,
        linux-omap@...r.kernel.org, Jonathan Corbet <corbet@....net>,
        Tony Lindgren <tony@...mide.com>,
        Richard Weinberger <richard@....at>,
        linux-gpio@...r.kernel.org, Aaro Koskinen <aaro.koskinen@....fi>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Marek Vasut <marek.vasut@...il.com>,
        linux-mtd@...ts.infradead.org,
        Miquel Raynal <miquel.raynal@...tlin.com>,
        Brian Norris <computersforpeace@...il.com>,
        David Woodhouse <dwmw2@...radead.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [RFC PATCH v2 07/12] mtd: rawnand: ams-delta: Set port direction once per transfer

Hi Boris,

On Tuesday, August 7, 2018 8:57:52 PM CEST Boris Brezillon wrote:
> On Tue,  7 Aug 2018 00:29:13 +0200
> Janusz Krzysztofik <jmkrzyszt@...il.com> wrote:
> 
> > In its current shape, the driver sets data port direction before each
> > byte read/write operation, even during multi-byte transfers.  Since
> > performance of the driver is completely not acceptable on Amstrad Delta
> > after it has been converted to GPIO bitbang, try to improve things a
> > bit by setting the port direction only on first byte of each transfer.
> ...
> I'd suggest a slightly different approach where the data pins
> direction state is stored in the the priv struct and only changed when
> required. This way you just have to add a test in
> ams_delta_read/write_byte().

Good idea, I'm going to use it, thanks.

Once done, may I also move that one earlier in the series so that it can be 
applied while our discussion on GPIO bitmap changes still continues?

Thanks,
Janusz