linux-kernel - Re: [PATCH] spi: bcm2835aux: Avoid 64-bit arithmetic in xfer len calc

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Date:   Wed, 14 Feb 2018 16:04:24 +0000
From:   Mark Brown <broonie@...nel.org>
To:     Trent Piepho <tpiepho@...inj.com>
Cc:     linux-spi@...r.kernel.org, linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        "Gustavo A . R . Silva" <garsilva@...eddedor.com>,
        Eric Anholt <eric@...olt.net>,
        Stefan Wahren <stefan.wahren@...e.com>,
        Florian Fainelli <f.fainelli@...il.com>,
        Ray Jui <rjui@...adcom.com>
Subject: Re: [PATCH] spi: bcm2835aux: Avoid 64-bit arithmetic in xfer len calc

On Mon, Feb 12, 2018 at 11:38:14AM -0800, Trent Piepho wrote:
> We want to check for xfers that are over 30 microseconds.  Rather than
> find how many µs a xfer will take, instead find how many bytes can be
> transferred in 30 µs.  The latter must be less than 32 bits (since our
> clock speed is limited to 32 bits), while the former involves 64 bit
> quantities and more arithmetic operations.

Please don't bury patches in the middle of existing threads, it makes it
much harder to find them.

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