Hi Joerg,
Joerg Roedel <joro@xxxxxxxxxx> wrote @ Mon, 4 Feb 2013 20:53:32 +0100:
> > static inline u32 smmu_read(struct smmu_device *smmu, size_t offs)
> > {
> > - BUG_ON(offs < 0x10);
> > - if (offs < 0x3c)
> > - return readl(smmu->regs[0] + offs - 0x10);
> > - BUG_ON(offs < 0x1f0);
> > - if (offs < 0x200)
> > - return readl(smmu->regs[1] + offs - 0x1f0);
> > - BUG_ON(offs < 0x228);
> > - if (offs < 0x284)
> > - return readl(smmu->regs[2] + offs - 0x228);
> > + int i;
> > +
> > + for (i = 0; i < smmu->nregs; i++) {
> > + void __iomem *addr = smmu->regbase + offs;
> > +
> > + BUG_ON(addr < smmu->regs[i]);
> > + if (addr <= smmu->rege[i])
> > + return readl(addr);
> > + }
>
> This loop is purely for checking offset to be valid. And this loop is
> repeated in the smmu_write() function. I queued a patch on-top to make
> this more clear. Please double-check:
Actually I did the similar thing in the first version of this patch(*1)
+static inline void smmu_check_reg_range(size_t offs)
+{
+ int i;
+
+ for (i = 0; i < smmu->nregs; i++) {
+ BUG_ON(offs < smmu->regs[i] - smmu->regbase);
+ if (offs <= smmu->rege[i] - smmu->regbase)
+ break;
+ }
+}
*1:
http://lists.linuxfoundation.org/pipermail/iommu/2013-January/005072.html
Then, Stehpen pointed out about this check function(*2).
"... here, you'd be doing the loop every access anyway, so you may as
well not calculate regbase at all, move the body of
smmu_check_reg_range() into smmu_read()/smmu_write(), and do the access
inside the if statement inside the loop, with the per-range mapping."
*2:
http://lists.linuxfoundation.org/pipermail/iommu/2013-January/005074.html
I might not get Stehpen's point in the latest patch(?), though....
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