Re: [PATCH 7/7] iommu/arm-smmu: Clear global and context bank fault status and syndrome registers

[Andreas Herrmann <andreas.herrmann-bsGFqQB8/DxBDgjK7y7TUQ@public.gmane.org>]

On Tue, Sep 24, 2013 at 11:42:52AM -0400, Will Deacon wrote:
> On Tue, Sep 24, 2013 at 04:07:01PM +0100, Andreas Herrmann wrote:
> > Signed-off-by: Andreas Herrmann <andreas.herrmann-bsGFqQB8/DxBDgjK7y7TUQ@public.gmane.org>
> > ---
> >  drivers/iommu/arm-smmu.c |    9 +++++++++
> >  1 file changed, 9 insertions(+)
> > 
> > diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> > index 251564e..a499146 100644
> > --- a/drivers/iommu/arm-smmu.c
> > +++ b/drivers/iommu/arm-smmu.c
> > @@ -645,6 +645,10 @@ static void arm_smmu_init_context_bank(struct arm_smmu_domain *smmu_domain)
> >  	stage1 = root_cfg->cbar != CBAR_TYPE_S2_TRANS;
> >  	cb_base = ARM_SMMU_CB_BASE(smmu) + ARM_SMMU_CB(smmu, root_cfg->cbndx);
> >  
> > +	/* clear fsr */
> > +	writel_relaxed(0xffffffff, cb_base + ARM_SMMU_CB_FSR);
> > +	writel_relaxed(0, cb_base + ARM_SMMU_CB_FSYNR0);
> > +
> >  	/* CBAR */
> >  	reg = root_cfg->cbar;
> >  	if (smmu->version == 1)
> > @@ -1570,6 +1574,11 @@ static void arm_smmu_device_reset(struct arm_smmu_device *smmu)
> >  	int i = 0;
> >  	u32 scr0 = readl_relaxed(gr0_base + ARM_SMMU_GR0_sCR0);
> >  
> > +	/* clear global FSRs */
> > +	writel(0xffffffff, gr0_base + ARM_SMMU_GR0_sGFSR);
> > +	writel(0, gr0_base + ARM_SMMU_GR0_sGFSYNR0);
> > +	writel(0, gr0_base + ARM_SMMU_GR0_sGFSYNR1);
> 
> Why do you need this?

According to the spec the status and syndrome registers have
unknown/unpredictable reset values. So better set known values before
we start to use these registers (ie. handle faults where we read
them). No?


Andreas