From: Peter Ujfalusi <peter.ujfalusi-l0cyMroinI0@public.gmane.org>
To: Greg Knight <g.knight-+7FPL3kuI1+B+jHODAdFcQ@public.gmane.org>
Cc: Mark Brown <broonie-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
<linux-spi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
"linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-omap-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
Subject: Re: Patch to parameterize DMA_MIN_BYTES for omap2-mcspi
Date: Fri, 20 Mar 2015 14:58:33 +0200 [thread overview]
Message-ID: <550C1979.5030208@ti.com> (raw)
In-Reply-To: <1426786080.13824.23.camel@symus-gk-mint>
On 03/19/2015 07:28 PM, Greg Knight wrote:
> Changing DMA_MIN_BYTES to, say, "dma_min_time_ms" sounds reasonable to
> me. I don't know how to compute it completely accurately as some SPI
> implementations I've seen seem to like to inject little delays between
> bytes for some reason, but a reasonable enough estimate should just be
> spi_transfer_time_ms = (bits * 1000) / spi_clock_speed.
>
> I would like to have the ability to configure it without a kernel
> recompile, though. Would a kernel param (module_param) be acceptable for
> this application?
Or sysfs interface as Mark suggested? But module_param should work as well.
> You don't happen to know the WL12xx SPI clock speed off the top of your
> head, do you?
In case of n900 it is 48000000 (board-rx51-peripherals.c). It is using 32bit
words over SPI.
Based on this and your experience I guess it is possible to come up with a
formula which satisfy both.
> Regards,
> Greg
>
--
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next prev parent reply other threads:[~2015-03-20 12:58 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-19 5:05 Patch to parameterize DMA_MIN_BYTES for omap2-mcspi Greg Knight
2015-03-19 9:47 ` Mark Brown
2015-03-19 12:34 ` Peter Ujfalusi
2015-03-19 13:16 ` Greg Knight
[not found] ` <CAAQQ3un3k-0nY8xaOXKbmCznOk69ZEhbWLd5ZZV1_=rQLOyspg-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2015-03-19 14:03 ` Mark Brown
2015-03-19 16:23 ` Peter Ujfalusi
[not found] ` <550AF7F6.7080200-l0cyMroinI0@public.gmane.org>
2015-03-19 17:28 ` Greg Knight
2015-03-19 18:51 ` Mark Brown
2015-03-20 13:10 ` Peter Ujfalusi
[not found] ` <550C1C2C.5080204-l0cyMroinI0@public.gmane.org>
2015-03-22 16:31 ` Mark Brown
2015-03-20 12:58 ` Peter Ujfalusi [this message]
2016-05-31 5:03 ` Anton Habegger
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