Re: [PATCH RESEND] usb: otg: OMAP4: Fix the omap4430_phy_set_clk function

[Tony Lindgren <tony@atomide.com>]

* Ruslan Bilovol <ruslan.bilovol@ti.com> [120629 14:55]:
> On Wed, Jun 20, 2012 at 4:31 PM, Tony Lindgren <tony@atomide.com> wrote:
> >
> > * Ruslan Bilovol <ruslan.bilovol@ti.com> [120612 10:42]:
> > > If the clocks are enabled and we want to enable them again
> > > omap4430_phy_set_clk disables them.
> > >
> > > Fix this - so now if we try to enable already enabled clocks
> > > it works correctly.
> >
> > Sounds like Felipe is on vacation. Trying to figure out if this
> > is something for the fixes branch:
> >
> > What happens if this not fixed, do you get some error?
> 
> The function is designed for simple clocks on-off:
> if zero "on" parameter is passed - switch the clocks off,
> if non-zero "on" parameter passed - switch the clocks on.
> 
> But due to error in implementation, it works wrong if called twice or more
> times with non-zero "on" parameter.
> 
> For example, assuming that clocks are disabled:
>     omap4430_phy_set_clk(dev, 1);   <=== enables clocks
>     omap4430_phy_set_clk(dev, 1);   <=== suddenly disables clocks,
> when we expect enabling.
>     omap4430_phy_set_clk(dev, 1);   <=== enables clocks again
> 
> It seems impact of this wrong behavior is not observed on current code
> base, but we see
> crashes caused by access to non-clocked registers when heavy use this function
> in the charger detection or after implementing otg EYE improvement.

Yes thanks for explaining. Can you please update the commit message a bit
with the explanation above?
 
> > Was this caused by some recent commit?
> 
> No, we have this wrong behavior since the omap_phy_internal.c file
> creation (c33fad0c37)

OK. It's probably safest to wait for Felipe to take a look at this
patch then and queue it for v3.6 -rc cycle.

Regards,

Tony

> > > Signed-off-by: Ruslan Bilovol <ruslan.bilovol@ti.com>
> > > ---
> > >  arch/arm/mach-omap2/omap_phy_internal.c |    2 +-
> > >  1 files changed, 1 insertions(+), 1 deletions(-)
> > >
> > > diff --git a/arch/arm/mach-omap2/omap_phy_internal.c
> > > b/arch/arm/mach-omap2/omap_phy_internal.c
> > > index 4c90477..0196683 100644
> > > --- a/arch/arm/mach-omap2/omap_phy_internal.c
> > > +++ b/arch/arm/mach-omap2/omap_phy_internal.c
> > > @@ -97,7 +97,7 @@ int omap4430_phy_set_clk(struct device *dev, int on)
> > >               clk_enable(clk48m);
> > >               clk_enable(clk32k);
> > >               state = 1;
> > > -     } else if (state) {
> > > +     } else if (!on && state) {
> > >               /* Disable the phy clocks */
> > >               clk_disable(phyclk);
> > >               clk_disable(clk48m);
> > > --
> > > 1.7.1
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