[PATCH V2 2/7] arm/imx6: add imx6q sabrelite board support

[s.hauer@pengutronix.de (Sascha Hauer)]

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.

Sascha


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