From: Ingo Oeser <ioe-lkml@rameria.de>
To: Joerg Roedel <joerg.roedel@amd.com>
Cc: mingo@redhat.com, tglx@linutronix.de, hpa@zytor.com,
linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org
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 [thread overview]
Message-ID: <200808142035.32422.ioe-lkml@rameria.de> (raw)
In-Reply-To: <1218736518-25301-2-git-send-email-joerg.roedel@amd.com>
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
next prev parent reply other threads:[~2008-08-14 18:42 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-08-14 17:55 [PATCH 0/4] AMD IOMMU updates for 2.6.27-rc3 Joerg Roedel
2008-08-14 17:55 ` [PATCH 1/4] AMD IOMMU: use status bit instead of memory write-back for completion wait Joerg Roedel
2008-08-14 18:35 ` Ingo Oeser [this message]
2008-08-14 20:02 ` Joerg Roedel
2008-08-14 17:55 ` [PATCH 2/4] AMD IOMMU: initialize device table properly Joerg Roedel
2008-08-14 17:55 ` [PATCH 3/4] AMD IOMMU: replace LOW_U32 macro with generic lower_32_bits Joerg Roedel
2008-08-14 17:55 ` [PATCH 4/4] AMD IOMMU: initialize dma_ops after sysfs registration Joerg Roedel
2008-08-15 11:57 ` [PATCH 0/4] AMD IOMMU updates for 2.6.27-rc3 Ingo Molnar
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