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Date:   Fri, 18 Dec 2020 20:44:14 +0000
From:   Mark Brown <broonie@kernel.org>
To:     Pratyush Yadav <p.yadav@ti.com>
Cc:     Sowjanya Komatineni <skomatineni@nvidia.com>,
        Boris Brezillon <boris.brezillon@collabora.com>,
        thierry.reding@gmail.com, jonathanh@nvidia.com, robh+dt@kernel.org,
        lukas@wunner.de, bbrezillon@kernel.org,
        tudor.ambarus@microchip.com, linux-spi@vger.kernel.org,
        linux-tegra@vger.kernel.org, linux-kernel@vger.kernel.org,
        devicetree@vger.kernel.org
Subject: Re: [PATCH v4 5/9] spi: spi-mem: Mark dummy transfers by setting
 dummy_data bit
Message-ID: <20201218204414.GG5333@sirena.org.uk>
References: <1608236927-28701-1-git-send-email-skomatineni@nvidia.com>
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On Fri, Dec 18, 2020 at 08:41:02PM +0000, Mark Brown wrote:
> On Sat, Dec 19, 2020 at 12:49:38AM +0530, Pratyush Yadav wrote:

> > Anyway, if the SPI maintainers think this is worth it, I won't object.

> This gets kind of circular, for me it's a question of if there's some
> meaningful benefit from using the feature vs the cost to support it and
> from the sounds of it we don't have numbers on the benefits from using
> it at present.

...although I do have to say looking at the implementation that the cost
seems low, it's just a flag set on an existing transfer.  The only issue
is if we'd get more win from coalesing the entire transaction (or entire
transmit) into a single transfer that could be DMAed and/or requires
fewer trips through the stack which does make it seem like an unclear
tradeoff from the point of view of client drivers

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