Messages in this thread | | | From | Ingo Oeser <> | Subject | Re: [PATCH 1/4] AMD IOMMU: use status bit instead of memory write-back for completion wait | Date | Thu, 14 Aug 2008 20:35:30 +0200 |
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Hi Joerg,
On Thursday 14 August 2008, Joerg Roedel wrote: > diff --git a/arch/x86/kernel/amd_iommu.c b/arch/x86/kernel/amd_iommu.c > index 22d7d05..028e945 100644 > --- a/arch/x86/kernel/amd_iommu.c > +++ b/arch/x86/kernel/amd_iommu.c > @@ -122,9 +119,15 @@ static int iommu_completion_wait(struct amd_iommu *iommu) > > while (!ready && (i < EXIT_LOOP_COUNT)) { > ++i; > - cpu_relax();
Could you elaborate, why you had to remove this?
Busy waiting loops should always do cpu_relay() to reduce heat procution and power consumption while idle.
> + /* wait for the bit to become one */ > + status = readl(iommu->mmio_base + MMIO_STATUS_OFFSET); > + ready = status & MMIO_STATUS_COM_WAIT_INT_MASK; > } >
Best Regards
Ingo Oeser
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