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From: Simon Horman <horms@verge.net.au>
To: linux-arm-kernel@lists.infradead.org
Subject: Re: [GIT PULL] Renesas ARM Based SoC Init Delay Updates For v3.18
Date: Tue, 09 Sep 2014 02:02:18 +0000	[thread overview]
Message-ID: <20140909020218.GA23233@verge.net.au> (raw)
In-Reply-To: <201409051727.18845.arnd@arndb.de>

On Fri, Sep 05, 2014 at 05:27:18PM +0200, Arnd Bergmann wrote:
> On Monday 25 August 2014, Simon Horman wrote:
> > Hi Olof, Hi Kevin, Hi Arnd,
> > 
> > Please consider these Renesas ARM based SoC init delay updates for v3.18.
> > 
> 
> While looking at your branches, I noticed that you go to great lengths
> to compute the correct lpj value and avoid the calibration.
> 
> However, I believe the "modern" way to do this is to call
> register_current_timer_delay() in order to base the delay loop
> on the hardware timer instead of looping in the CPU. This is
> more accurate and more robust against CPU frequency scaling.

I may be wrong but my understanding is that Renesas SoCs may be
booted without a timer.

> I'm applying the patches now, but it's something you may want
> to look at in the future. On a related topic, your clocksource
> drivers could be simplified for the DT-only case by using
> CLOCKSOURCE_OF_DECLARE() instead of early_platform_init(), but
> I don't know what the impact would be for the arch/sh and legacy
> mach-shmobile cases.

Thanks, I will have that looked into.

WARNING: multiple messages have this Message-ID (diff)
From: horms@verge.net.au (Simon Horman)
To: linux-arm-kernel@lists.infradead.org
Subject: [GIT PULL] Renesas ARM Based SoC Init Delay Updates For v3.18
Date: Tue, 9 Sep 2014 11:02:18 +0900	[thread overview]
Message-ID: <20140909020218.GA23233@verge.net.au> (raw)
In-Reply-To: <201409051727.18845.arnd@arndb.de>

On Fri, Sep 05, 2014 at 05:27:18PM +0200, Arnd Bergmann wrote:
> On Monday 25 August 2014, Simon Horman wrote:
> > Hi Olof, Hi Kevin, Hi Arnd,
> > 
> > Please consider these Renesas ARM based SoC init delay updates for v3.18.
> > 
> 
> While looking at your branches, I noticed that you go to great lengths
> to compute the correct lpj value and avoid the calibration.
> 
> However, I believe the "modern" way to do this is to call
> register_current_timer_delay() in order to base the delay loop
> on the hardware timer instead of looping in the CPU. This is
> more accurate and more robust against CPU frequency scaling.

I may be wrong but my understanding is that Renesas SoCs may be
booted without a timer.

> I'm applying the patches now, but it's something you may want
> to look at in the future. On a related topic, your clocksource
> drivers could be simplified for the DT-only case by using
> CLOCKSOURCE_OF_DECLARE() instead of early_platform_init(), but
> I don't know what the impact would be for the arch/sh and legacy
> mach-shmobile cases.

Thanks, I will have that looked into.

  reply	other threads:[~2014-09-09  2:02 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-08-25  1:10 [GIT PULL] Renesas ARM Based SoC Init Delay Updates For v3.18 Simon Horman
2014-08-25  1:10 ` Simon Horman
2014-08-25  1:10 ` [PATCH 01/10] ARM: shmobile: sh7372: Update DTS to include CPU frequency Simon Horman
2014-08-25  1:10   ` Simon Horman
2014-08-25  1:10 ` [PATCH 02/10] ARM: shmobile: sh73a0: " Simon Horman
2014-08-25  1:10   ` Simon Horman
2014-08-25  1:10 ` [PATCH 03/10] ARM: shmobile: r8a7778: " Simon Horman
2014-08-25  1:10   ` Simon Horman
2014-08-25  1:10 ` [PATCH 04/10] ARM: shmobile: sh7372: Use shmobile_init_delay() Simon Horman
2014-08-25  1:10   ` Simon Horman
2014-08-25  1:10 ` [PATCH 05/10] ARM: shmobile: r8a73a4: " Simon Horman
2014-08-25  1:10   ` Simon Horman
2014-08-25  1:10 ` [PATCH 06/10] ARM: shmobile: Remove shmobile_setup_delay() Simon Horman
2014-08-25  1:10   ` Simon Horman
2014-08-25  1:10 ` [PATCH 07/10] ARM: shmobile: sh73a0: Use shmobile_init_delay() Simon Horman
2014-08-25  1:10   ` Simon Horman
2014-08-25  1:10 ` [PATCH 08/10] ARM: shmobile: r8a7778: " Simon Horman
2014-08-25  1:10   ` Simon Horman
2014-08-25  1:10 ` [PATCH 09/10] ARM: shmobile: bockw: " Simon Horman
2014-08-25  1:10   ` Simon Horman
2014-08-25  1:10 ` [PATCH 10/10] ARM: shmobile: kzm9g: " Simon Horman
2014-08-25  1:10   ` Simon Horman
2014-09-05 15:27 ` [GIT PULL] Renesas ARM Based SoC Init Delay Updates For v3.18 Arnd Bergmann
2014-09-05 15:27   ` Arnd Bergmann
2014-09-09  2:02   ` Simon Horman [this message]
2014-09-09  2:02     ` Simon Horman
2014-09-09  8:50     ` Arnd Bergmann
2014-09-09  8:50       ` Arnd Bergmann
2014-09-05 16:13 ` Arnd Bergmann
2014-09-05 16:13   ` Arnd Bergmann

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