From: Russell King - ARM Linux <linux-lFZ/pmaqli7XmaaqVzeoHQ@public.gmane.org>
To: Peter Griffin <peter.griffin-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
Cc: Lee Jones <lee.jones-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>,
devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
kernel-F5mvAk5X5gdBDgjK7y7TUQ@public.gmane.org,
rtc-linux-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
wim-IQzOog9fTRqzQB+pC5nmwQ@public.gmane.org,
linux-0h96xk9xTtrk1uMJSBkQmQ@public.gmane.org,
linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
linux-watchdog-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [STLinux Kernel] [PATCH v3 7/8] rtc: st: add new driver for ST's LPC RTC
Date: Wed, 25 Feb 2015 11:19:11 +0000 [thread overview]
Message-ID: <20150225111910.GX8656@n2100.arm.linux.org.uk> (raw)
In-Reply-To: <20150223101223.GA14142@griffinp-ThinkPad-X1-Carbon-2nd>
On Mon, Feb 23, 2015 at 10:12:23AM +0000, Peter Griffin wrote:
> I think all the writel IO accessors in this driver can be replaced
> with the *_relaxed variant. This will avoid the overhead of taking a
> spinlock in the l2 outer cache part of writel.
You're really operating on old information. With much improved L2 cache
support code which went in a year or so ago, for the popular L2 cache
controllers, we don't take a spinlock anymore - we just write to the
register directly.
The spinlock is only present for L2C-220 controllers, which are rare.
Moreover, taking the spinlock is only expensive if you have things like
lockdep enabled, otherwise it should be inline and will be fast.
However, using the _relaxed variants where we can get away with weaker
ordering of the writes to the device is a good thing nevertheless. I'm
just pointing out that your reasoning above is wrong.
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next prev parent reply other threads:[~2015-02-25 11:19 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-18 11:49 [PATCH v3 0/8] mfd: watchdog: rtc: New driver for ST's LPC IP Lee Jones
2015-02-18 11:49 ` [PATCH v3 1/8] ARM: multi_v7_defconfig: Enable support for ST's LPC Watchdog Lee Jones
2015-02-18 11:49 ` [PATCH v3 2/8] ARM: multi_v7_defconfig: Enable support for ST's LPC RTC Lee Jones
2015-02-18 11:49 ` [PATCH v3 3/8] ARM: STi: DT: STiH407: Add Device Tree node for the LPC Lee Jones
2015-02-18 11:49 ` [PATCH v3 4/8] watchdog: bindings: Provide ST bindings for ST's LPC Watchdog device Lee Jones
2015-02-18 11:49 ` [PATCH v3 5/8] watchdog: st_wdt: Add new driver for ST's LPC Watchdog Lee Jones
2015-02-23 10:25 ` [STLinux Kernel] " Peter Griffin
2015-03-02 7:56 ` Peter Griffin
2015-02-23 19:50 ` [v3,5/8] " Guenter Roeck
[not found] ` <1424260154-12868-1-git-send-email-lee.jones-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
2015-02-18 11:49 ` [PATCH v3 6/8] rtc: bindings: Provide ST bindings for ST's LPC RTC device Lee Jones
2015-02-18 11:49 ` [PATCH v3 7/8] rtc: st: add new driver for ST's LPC RTC Lee Jones
[not found] ` <1424260154-12868-8-git-send-email-lee.jones-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
2015-02-23 10:12 ` [STLinux Kernel] " Peter Griffin
2015-02-25 11:08 ` Lee Jones
2015-02-25 11:19 ` Russell King - ARM Linux [this message]
2015-02-25 14:28 ` Peter Griffin
2015-02-18 11:49 ` [PATCH v3 8/8] MAINTAINERS: Add Watchdog and RTC files to STI's maintainer entry Lee Jones
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