[PATCH] ARM: imx6: add opp table when cpufreq is enabled

[shawnguo@kernel.org (Shawn Guo)]

On Mon, Aug 29, 2016 at 08:49:04AM +0000, Yongcai Huang wrote:
> 
> > -----Original Message-----
> > From: Shawn Guo [mailto:shawnguo at kernel.org]
> > Sent: 2016-08-29 2:27 PM
> > To: Yongcai Huang <anson.huang@nxp.com>
> > Cc: Fabio Estevam <fabio.estevam@nxp.com>; Peter Chen
> > <peter.chen@nxp.com>; linux at armlinux.org.uk; linux-arm-
> > kernel at lists.infradead.org; kernel at pengutronix.de
> > Subject: Re: [PATCH] ARM: imx6: add opp table when cpufreq is enabled
> > 
> > On Mon, Aug 29, 2016 at 02:19:10PM +0800, Shawn Guo wrote:
> > > On Tue, Aug 23, 2016 at 10:56:11PM +0800, Anson Huang wrote:
> > > > On those i.MX6 platforms which have no speed grading check, opp
> > > > table will NOT be created in platform code, so cpufreq driver will
> > > > have below error message:
> > > >
> > > > cpu cpu0: dev_pm_opp_get_opp_count: OPP table not found (-19)
> > >
> > > The cpufreq driver calls dev_pm_opp_get_opp_count() to test if
> > > platform supplies an OPP table.  If not, the driver will call into
> > > dev_pm_opp_of_add_table() on its own.  So this is not an error
> > > message, and cpufreq driver should just work fine on i.MX6SX and i.MX6SL.
> > 
> > If you think the message might confuse people, we can add an info message in
> > cpufreq driver in case it adds OPP table by its own, which can explain the 'error'
> > message a bit from dev_pm_opp_get_opp_count().
> > 
> > Shawn
> 
> After rethink this, if we can avoid this "error" message printed out from common OPP
> framework, why NOT do it? Although the code change is kind of big, but the logic is
> quite simple. Adding info message in cpufreq driver is a bit better, but the "error" message
> is still there which may concern some people who really care about it, adding this patch
> would make it easier for our future kernel upgrade.
> 
> Actually, if we do NOT have speed grading fuse check need for some platforms, the opp
> table init can be put in cpufreq for all platforms, so I think the best way is to put
> all opp table init in either platform code or cpufreq driver, some platforms put it in platform
> code and some in cpufreq driver is NOT the best. 

It will be the best if we can have cpufreq driver handle OPP table for
all i.MX6 cases.

My problem with the platform approach is that every time we have a new
platform support, we need to patch platform code to add OPP table.
That's not good.

Shawn