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From: Mark Brown <broonie-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
To: Douglas Anderson <dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
Cc: drinkcat-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org,
	briannorris-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-rockchip-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
	mka-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org,
	Enric Balletbo i Serra
	<enric.balletbo-ZGY8ohtN/8qB+jHODAdFcQ@public.gmane.org>,
	Guenter Roeck <groeck-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
	Benson Leung <bleung-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
Subject: Re: [PATCH 1/4] spi: For controllers that need realtime always use the pump thread
Date: Sun, 12 May 2019 16:33:01 +0900	[thread overview]
Message-ID: <20190512073301.GC21483@sirena.org.uk> (raw)
In-Reply-To: <20190510223437.84368-2-dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>


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On Fri, May 10, 2019 at 03:34:34PM -0700, Douglas Anderson wrote:
> If a controller specifies that it needs high priority for sending
> messages we should always schedule our transfers on the thread.  If we
> don't do this we'll do the transfer in the caller's context which
> might not be very high priority.

If performance is important you probably also want to avoid the context
thrashing - executing in the calling context is generally a substantial
performance boost.  I can see this causing problems further down the
line when someone else turns up with a different requirement, perhaps in
an application where the caller does actually have a raised priority
themselves and just wanted to make sure that the thread wasn't lower
than they are.  I guess it'd be nice if we could check what priority the
calling thread has and make a decision based on that but there don't
seem to be any facilities for doing that which I can see right now.

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  parent reply	other threads:[~2019-05-12  7:33 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-10 22:34 [PATCH 0/4] spi: A better solution for cros_ec_spi reliability Douglas Anderson
2019-05-10 22:34 ` [PATCH 1/4] spi: For controllers that need realtime always use the pump thread Douglas Anderson
2019-05-11  0:24   ` Guenter Roeck
     [not found]   ` <20190510223437.84368-2-dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
2019-05-12  7:33     ` Mark Brown [this message]
2019-05-13 20:24       ` Doug Anderson
2019-05-14  9:30         ` Mark Brown
2019-05-14 14:42           ` Doug Anderson
2019-05-14 15:06             ` Mark Brown
2019-05-10 22:34 ` [PATCH 2/4] spi: Allow SPI devices to specify that they are timing sensitive Douglas Anderson
     [not found]   ` <20190510223437.84368-3-dianders-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
2019-05-11  0:31     ` Guenter Roeck
2019-05-12  7:42     ` Mark Brown

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