From mboxrd@z Thu Jan  1 00:00:00 1970
From: richard.zhao@linaro.org (Richard Zhao)
Date: Wed, 14 Dec 2011 22:11:11 +0800
Subject: [PATCH V2 2/7] arm/imx6: add imx6q sabrelite board support
In-Reply-To: <20111214110558.GE27267@pengutronix.de>
References: <1323757530-19402-1-git-send-email-richard.zhao@linaro.org>
 <1323757530-19402-3-git-send-email-richard.zhao@linaro.org>
 <20111213115648.GA10022@S2101-09.ap.freescale.net>
 <20111213125353.GB1757@richard-laptop>
 <20111213133348.GA14688@S2101-09.ap.freescale.net>
 <20111214110558.GE27267@pengutronix.de>
Message-ID: <20111214141109.GB1700@richard-laptop>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

On Wed, Dec 14, 2011 at 12:05:58PM +0100, Sascha Hauer wrote:
> On Tue, Dec 13, 2011 at 09:33:50PM +0800, Shawn Guo wrote:
> > On Tue, Dec 13, 2011 at 08:54:01PM +0800, Richard Zhao wrote:
> > > > > +	cpus {
> > > > > +		cpu at 0 {
> > > > > +			clock-frequency = <996000000>;
> > > > > +		};
> > > > 
> > > > I do not follow why we need to have cpu frequency encoded in board
> > > > level dts.  To me, what frequency the cpu is capable of running at
> > > > is really soc specific thing.  So putting this data in
> > > > imx6q-sabrelite.dts is kinda suggesting that imx6q soc on this
> > > > sabrelite board can run at 996000000, while on other boards like
> > > > sabreauto/arm2 can only run at other frequency.  This is seems different
> > > > from what I heard from Freescale internal development team.
> > > 1G operation needs a certain external voltage condition, though we have
> > > internal regulater. Boards that don't meet the condition have to fall back
> > > to lower frequency.
> > > From software side view, I refer to Freescale software release. please see
> > > http://opensource.freescale.com/git?p=imx/linux-2.6-imx.git;a=blob;f=arch/arm/mach-mx6/cpu_op-mx6.c;h=30a4346282ea5c332b4c48bf6a2d644abd9f31db;hb=imx_2.6.38_11.11.01
> > > 
> > > and for imx53, there' also different max freq board:
> > > http://opensource.freescale.com/git?p=imx/linux-2.6-imx.git;a=blob;f=arch/arm/mach-mx5/mx53_wp.c;h=a63bae42fb661c161cab99d61f4a3108305b0f55;hb=refs/heads/imx_2.6.35_11.09.01
> > > 
> > > IMHO, even the board has limitations, we'd better give an option to support
> > > it if it's possible.
> > > 
> > I understand all these things.  What I was suggesting is this option
> > should not be provided by the dts at all.
> 
> Yes. If it's not provided the cpufreq layer should either assume 800MHz
> is the highest value which is safe on all boards or it could read the
> current frequency from the hardware. If this is 1GHz this value is
> obviously safe.
Actually, you'd better not depend on uboot to setting the highest cpu freq.
At least current freescale internel uboot don't set 1G.

Thanks
Richard
> 
> Sascha
> 
> 
> -- 
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