From: Mattias Wallin <mattias.wallin@stericsson.com>
To: Stephen Boyd <sboyd@codeaurora.org>
Cc: Russell King <linux@arm.linux.org.uk>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-arm-msm@vger.kernel.org" <linux-arm-msm@vger.kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
Saravana Kannan <skannan@codeaurora.org>,
Andrew Morton <akpm@linux-foundation.org>,
Linus Walleij <linus.walleij@linaro.org>
Subject: Re: [PATCHv5 1/3] ARM: Translate delay.S into (mostly) C
Date: Thu, 7 Apr 2011 09:29:57 +0200 [thread overview]
Message-ID: <4D9D67F5.8030703@stericsson.com> (raw)
In-Reply-To: <1302047800-26720-2-git-send-email-sboyd@codeaurora.org>
On 04/06/2011 01:56 AM, Stephen Boyd wrote:
> We want to allow machines to override the __delay() implementation
> at runtime so they can use a timer based __delay() routine. It's
> easier to do this using C, so let's write udelay and friends in C.
>
> We lose the #if 0 code, which according to Russell is used "to
> make the delay loop more stable and predictable on older CPUs"
> (seehttp://article.gmane.org/gmane.linux.kernel/888867 for more
> info). We shouldn't be too worried though, since we'll soon add
> functionality allowing a machine to set the __delay() loop
> themselves, thus allowing machines to resurrect the commented out
> code should they need it.
>
> Nicolas expressed concern that fixed lpj cmdlines will break due to
> compiler optimizations. That doesn't seem to be the case since
> before and after this patch I get the same lpj value when running
> my CPU at 19.2 MHz. That should be sufficiently slow enough to
> cover any machine running Linux.
Tested-by: Mattias Wallin <mattias.wallin@stericsson.com>
Yours,
Mattias Wallin
WARNING: multiple messages have this Message-ID (diff)
From: mattias.wallin@stericsson.com (Mattias Wallin)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCHv5 1/3] ARM: Translate delay.S into (mostly) C
Date: Thu, 7 Apr 2011 09:29:57 +0200 [thread overview]
Message-ID: <4D9D67F5.8030703@stericsson.com> (raw)
In-Reply-To: <1302047800-26720-2-git-send-email-sboyd@codeaurora.org>
On 04/06/2011 01:56 AM, Stephen Boyd wrote:
> We want to allow machines to override the __delay() implementation
> at runtime so they can use a timer based __delay() routine. It's
> easier to do this using C, so let's write udelay and friends in C.
>
> We lose the #if 0 code, which according to Russell is used "to
> make the delay loop more stable and predictable on older CPUs"
> (seehttp://article.gmane.org/gmane.linux.kernel/888867 for more
> info). We shouldn't be too worried though, since we'll soon add
> functionality allowing a machine to set the __delay() loop
> themselves, thus allowing machines to resurrect the commented out
> code should they need it.
>
> Nicolas expressed concern that fixed lpj cmdlines will break due to
> compiler optimizations. That doesn't seem to be the case since
> before and after this patch I get the same lpj value when running
> my CPU at 19.2 MHz. That should be sufficiently slow enough to
> cover any machine running Linux.
Tested-by: Mattias Wallin <mattias.wallin@stericsson.com>
Yours,
Mattias Wallin
next prev parent reply other threads:[~2011-04-07 7:30 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-04-05 23:56 [PATCHv5 0/3] Constant udelay() for SMP and non-SMP systems Stephen Boyd
2011-04-05 23:56 ` Stephen Boyd
2011-04-05 23:56 ` [PATCHv5 1/3] ARM: Translate delay.S into (mostly) C Stephen Boyd
2011-04-05 23:56 ` Stephen Boyd
2011-04-06 8:49 ` Mattias Wallin
2011-04-06 8:49 ` Mattias Wallin
2011-04-06 17:34 ` Stephen Boyd
2011-04-06 17:34 ` Stephen Boyd
2011-04-07 1:27 ` Saravana Kannan
2011-04-07 1:27 ` Saravana Kannan
2011-04-07 7:27 ` Mattias Wallin
2011-04-07 7:27 ` Mattias Wallin
2011-04-07 7:27 ` Mattias Wallin
2011-04-07 7:29 ` Mattias Wallin [this message]
2011-04-07 7:29 ` Mattias Wallin
2011-04-05 23:56 ` [PATCHv5 2/3] ARM: Allow machines to override __delay() Stephen Boyd
2011-04-05 23:56 ` Stephen Boyd
2011-04-07 7:30 ` Mattias Wallin
2011-04-07 7:30 ` Mattias Wallin
2011-04-07 7:30 ` Mattias Wallin
2011-04-05 23:56 ` [PATCHv5 3/3] ARM: Implement a timer based __delay() loop Stephen Boyd
2011-04-05 23:56 ` Stephen Boyd
2011-04-07 7:30 ` Mattias Wallin
2011-04-07 7:30 ` Mattias Wallin
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