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SubjectRe: [PATCH v2 2/3] ARM: tegra: Add SMMU enabler in AHB
From: Felipe Balbi <balbi@ti.com>
Subject: Re: [PATCH v2 2/3] ARM: tegra: Add SMMU enabler in AHB
Date: Tue, 24 Apr 2012 14:41:18 +0200
Message-ID: <20120424124115.GL8444@arwen.pp.htv.fi>

> * PGP Signed by an unknown key
>
> On Tue, Apr 24, 2012 at 02:39:30PM +0200, Hiroshi Doyu wrote:
> > From: Felipe Balbi <balbi@ti.com>
> > Subject: Re: [PATCH v2 2/3] ARM: tegra: Add SMMU enabler in AHB
> > Date: Tue, 24 Apr 2012 14:32:52 +0200
> > Message-ID: <20120424123248.GG8444@arwen.pp.htv.fi>
> >
> > > > Old Signed by an unknown key
> > >
> > > Hi,
> > >
> > > On Tue, Apr 24, 2012 at 03:05:15PM +0300, Hiroshi DOYU wrote:
> > > > @@ -95,6 +98,21 @@ static inline void gizmo_writel(unsigned long value, unsigned long offset)
> > > > writel(value, tegra_ahb->regs + offset);
> > > > }
> > > >
> > > > +#ifdef CONFIG_ARCH_TEGRA_3x_SOC
> > > > +
> > > > +void tegra_ahb_enable_smmu(void)
> > > > +{
> > > > + unsigned long val;
> > > > +
> > > > + val = gizmo_readl(AHB_ARBITRATION_XBAR_CTRL);
> > > > + val |= AHB_ARBITRATION_XBAR_CTRL_SMMU_INIT_DONE_DONE <<
> > > > + AHB_ARBITRATION_XBAR_CTRL_SMMU_INIT_DONE_SHIFT;
> > > > + gizmo_writel(val, AHB_ARBITRATION_XBAR_CTRL);
> > > > +}
> > > > +EXPORT_SYMBOL(tegra_ahb_enable_smmu);
> > >
> > > ok, so this is the only place where you need that global pointer. Who
> > > would call this ? Can you do runtime detection of the SoC and enable
> > > SMMU based on that ?
> > >
> > > I mean, will this function always be called for TEGRA 3 SoCs or is there
> > > another condition to that ?
> >
> > Only Tegra3 has SMMU.
>
> but all of them ? In that case, you could call this from probe itself,
> right ? But an ifdef won't work in all cases, so you need to do runtime
> detection based on some revision register or cpu detection...

So far we don't have so many variants, and presently TEGRA_3x_SOC
always has a SMMU. If there were some variants of TEGRA_3x_SOC, where
some might not have SMMU, then runtime detection would make sense
there. Now it's something like TEGRA_3x_SOC == SMMU.


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