From: Grant Likely <grant.likely-s3s/WqlpOiPyB63q8FvJNQ@public.gmane.org>
To: Gabor Juhos <juhosg-p3rKhJxN3npAfugRpC6u6w@public.gmane.org>
Cc: spi-devel-general-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org,
Gabor Juhos <juhosg-p3rKhJxN3npAfugRpC6u6w@public.gmane.org>
Subject: Re: [PATCH 1/6] spi/ath79: add delay between SCK changes
Date: Tue, 05 Feb 2013 12:57:19 +0000 [thread overview]
Message-ID: <20130205125719.878EE3E0E27@localhost> (raw)
In-Reply-To: <1356601349-23617-2-git-send-email-juhosg-p3rKhJxN3npAfugRpC6u6w@public.gmane.org>
On Thu, 27 Dec 2012 10:42:24 +0100, Gabor Juhos <juhosg-p3rKhJxN3npAfugRpC6u6w@public.gmane.org> wrote:
> The driver uses the "as fast as it can" approach
> to drive the SCK signal. However this does not
> work with certain low speed SPI chips (e.g. the
> PCF2123 RTC chip).
>
> The patch adds per-bit slowdowns in order to be
> able to use the driver with such chips as well.
>
> Signed-off-by: Gabor Juhos <juhosg-p3rKhJxN3npAfugRpC6u6w@public.gmane.org>
I've applied this, but please take a second look to make sure you're not
doing something unintended. The ndelay call will spin until it
completes. If the current context is interrupted or scheduled out then
it will still spin when it gets back. You may be wasting more time than
is necessary. It would be better to check the wall time over a loop
iteration. And if the delay required is large, then it should sleep.
g.
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next prev parent reply other threads:[~2013-02-05 12:57 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-12-27 9:42 [PATCH 0/6] spi/ath79: various fixes Gabor Juhos
[not found] ` <1356601349-23617-1-git-send-email-juhosg-p3rKhJxN3npAfugRpC6u6w@public.gmane.org>
2012-12-27 9:42 ` [PATCH 1/6] spi/ath79: add delay between SCK changes Gabor Juhos
[not found] ` <1356601349-23617-2-git-send-email-juhosg-p3rKhJxN3npAfugRpC6u6w@public.gmane.org>
2013-02-05 12:57 ` Grant Likely [this message]
2013-02-05 19:52 ` Gabor Juhos
2012-12-27 9:42 ` [PATCH 2/6] spi/ath79: add missing HIGH->LOW SCK transition Gabor Juhos
[not found] ` <1356601349-23617-3-git-send-email-juhosg-p3rKhJxN3npAfugRpC6u6w@public.gmane.org>
2013-02-05 12:57 ` Grant Likely
2012-12-27 9:42 ` [PATCH 3/6] spi/ath79: remove superfluous chip select code Gabor Juhos
[not found] ` <1356601349-23617-4-git-send-email-juhosg-p3rKhJxN3npAfugRpC6u6w@public.gmane.org>
2013-02-05 12:58 ` Grant Likely
2012-12-27 9:42 ` [PATCH 4/6] spi/ath79: use gpio_request_one Gabor Juhos
[not found] ` <1356601349-23617-5-git-send-email-juhosg-p3rKhJxN3npAfugRpC6u6w@public.gmane.org>
2013-02-05 12:59 ` Grant Likely
2012-12-27 9:42 ` [PATCH 5/6] spi/ath79: avoid multiple initialization of the SPI controller Gabor Juhos
[not found] ` <1356601349-23617-6-git-send-email-juhosg-p3rKhJxN3npAfugRpC6u6w@public.gmane.org>
2013-02-05 13:00 ` Grant Likely
2012-12-27 9:42 ` [PATCH 6/6] spi/ath79: add shutdown handler Gabor Juhos
[not found] ` <1356601349-23617-7-git-send-email-juhosg-p3rKhJxN3npAfugRpC6u6w@public.gmane.org>
2013-02-05 13:02 ` Grant Likely
2013-02-05 19:53 ` Gabor Juhos
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