From: Wolfram Sang <w.sang-bIcnvbaLZ9MEGnE8C9+IrQ@public.gmane.org>
To: Mark Brown
<broonie-yzvPICuk2AATkU/dhu1WVueM+bqZidxxQQ4Iyu8u01E@public.gmane.org>
Cc: Daniel Kurtz <djkurtz-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
Olof Johansson <olofj-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
Benson Leung <bleung-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
Doug Anderson <dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
linux-i2c-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH] i2c: i2c-s3c2410: Remove recently introduced performance overheads
Date: Thu, 22 Nov 2012 22:35:03 +0100 [thread overview]
Message-ID: <20121122213503.GB14851@pengutronix.de> (raw)
In-Reply-To: <1353471131-23975-1-git-send-email-broonie-yzvPICuk2AATkU/dhu1WVueM+bqZidxxQQ4Iyu8u01E@public.gmane.org>
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On Wed, Nov 21, 2012 at 01:12:11PM +0900, Mark Brown wrote:
> The changes in "i2c-s3c2410: use exponential back off while polling for
> bus idle" remove the initial busy wait for I2C transfers to complete and
> replace it with usleep_range() calls which will schedule.
>
> Since for older SoCs I2C transfers would usually complete within an
> extremely small number of CPU cycles there is a win from not having to
> schedule. This happens because on the older SoCs the cores run at a
> smaller multiple of the speeds that the I2C bus is operating at; on more
> modern SoCs the busy wait is less likely to be effective.
>
> Fix the issue by restoring the busy wait, reducing the number of spins
> from 20 to 3 which covers the overwhelming majority of I2C transfers on
> the SoCs where the busy wait is effective.
>
> Signed-off-by: Mark Brown <broonie-yzvPICuk2AATkU/dhu1WVueM+bqZidxxQQ4Iyu8u01E@public.gmane.org>
Applied to for-next, thanks everyone!
--
Pengutronix e.K. | Wolfram Sang |
Industrial Linux Solutions | http://www.pengutronix.de/ |
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next prev parent reply other threads:[~2012-11-22 21:35 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-21 4:12 [PATCH] i2c: i2c-s3c2410: Remove recently introduced performance overheads Mark Brown
[not found] ` <1353471131-23975-1-git-send-email-broonie-yzvPICuk2AATkU/dhu1WVueM+bqZidxxQQ4Iyu8u01E@public.gmane.org>
2012-11-21 5:08 ` Olof Johansson
[not found] ` <CAOesGMhBZo6gKfzs1A954a_vaAMzy4px3TsgKE2rac_igH3sLw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-11-21 6:23 ` Daniel Kurtz
2012-11-22 21:35 ` Wolfram Sang [this message]
-- strict thread matches above, loose matches on Subject: below --
2012-11-20 5:57 Mark Brown
[not found] ` <1353391041-28943-1-git-send-email-broonie-yzvPICuk2AATkU/dhu1WVueM+bqZidxxQQ4Iyu8u01E@public.gmane.org>
2012-11-20 9:45 ` Daniel Kurtz
[not found] ` <CAGS+omAkOwq7m_zGCYjwgrFY_jjNfWqvFqS29F5b6GBPr62UFg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-11-20 9:48 ` Mark Brown
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