[PATCH] ARM: OMAP3: Fix iva2_pwrdm settings for 3703

[Mark A. Greer]

On Wed, May 15, 2013 at 10:07:35AM -0700, Tony Lindgren wrote:
> * Mark A. Greer <mgreer at animalcreek.com> [130514 18:57]:
> > On Tue, May 14, 2013 at 05:25:37PM -0700, Tony Lindgren wrote:
> > > Commit a819c4f1 (ARM: OMAP3: PM: Only access IVA if one exists)
> > > changed PM to not access IVA registers on omaps that don't have
> > > them. Turns out we still need to idle iva2 as otherwise iva2_pwrdm
> > > will stay on and block deeper idle states.
> > > 
> > > Signed-off-by: Tony Lindgren <tony at atomide.com>
> > > 
> > > ---
> > > 
> > > Paul & Kevin, do you have better ideas for fixing this?
> > > 
> > > --- a/arch/arm/mach-omap2/pm34xx.c
> > > +++ b/arch/arm/mach-omap2/pm34xx.c
> > > @@ -546,8 +546,10 @@ static void __init prcm_setup_regs(void)
> > >  	/* Clear any pending PRCM interrupts */
> > >  	omap2_prm_write_mod_reg(0, OCP_MOD, OMAP3_PRM_IRQSTATUS_MPU_OFFSET);
> > >  
> > > -	if (omap3_has_iva())
> > > -		omap3_iva_idle();
> > > +	/*
> > > +	 * We need to idle iva2_pwrdm even on am3703 with no iva2.
> > > +	 */
> > > +	omap3_iva_idle();
> > >  
> > >  	omap3_d2d_idle();
> > >  }
> > 
> > [Kevin, Paul, some background: Tony discovered that the am3703 needs
> > to have omap3_iva_idle() called even though its not supposed to have
> > an IVA.]
> > 
> > This is potentially bad for other SoC's that don't have an IVA so I don't
> > think its the way to go.  My preference would be to set the OMAP3_HAS_IVA
> > flag for the am3703 only since its the one with the bug.  Maybe something
> > in id.c:omap3xxx_check_features() but I don't see any existing way to check
> > for an am3703 vs. other am37xx SoCs.  Any ideas?
> > 
> > Another option, I suppose, is a dts entry but I don't like that at all.
> 
> It seems that iva2_pwrdm is there for all omap3 even if OMAP3_HAS_IVA
> flag is unset. And if that's the case, iva2 clocks still need to be idled
> in all cases.

Ahh, this takes us to the "Great TI Docs Mystery" :) -- its basically
impossible to tell because despite what their docs may say, the hardware
can be quite different.  I'm not sure how to proceed other than trial &
error with as many different SoCs as we can find.

> It's possible that not all steps in omap3_iva_idle() are needed though.
> I can debug further to see which part of the omap3_iva_idle() are needed.
> 
> Mark, do you have some omap3 with no iva (other than am3703) to test the
> idle states with?

I have an am35xx which isn't supposed to have an IVA so I can test with it
(although, I'm not sure how well the kernel works on the am35xx these days).

I'm a bit busy today but I'll try booting the am35xx tomorrow and if it
comes up, see what I can figure out.

Mark
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