linux-kernel - Re: [PATCH v2 2/3] ARM: tegra: Add SMMU enabler in AHB

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Date:	Tue, 24 Apr 2012 15:41:18 +0300
From:	Felipe Balbi <balbi@...com>
To:	Hiroshi Doyu <hdoyu@...dia.com>
Cc:	"balbi@...com" <balbi@...com>,
	"linux-tegra@...r.kernel.org" <linux-tegra@...r.kernel.org>,
	"ccross@...roid.com" <ccross@...roid.com>,
	"olof@...om.net" <olof@...om.net>,
	"swarren@...dotorg.org" <swarren@...dotorg.org>,
	"linux@....linux.org.uk" <linux@....linux.org.uk>,
	"tony@...mide.com" <tony@...mide.com>,
	"hsweeten@...ionengravers.com" <hsweeten@...ionengravers.com>,
	"jamie@...ieiles.com" <jamie@...ieiles.com>,
	"rob.herring@...xeda.com" <rob.herring@...xeda.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/3] ARM: tegra: Add SMMU enabler in AHB

On Tue, Apr 24, 2012 at 02:39:30PM +0200, Hiroshi Doyu wrote:
> From: Felipe Balbi <balbi@...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@...en.pp.htv.fi>
> 
> > * PGP 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...

-- 
balbi

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