x86/pci-dma: remove the explicit nodac and allowdac option
This is something drivers should decide (modulo chipset quirks like for VIA), which as far as I can tell is how things have been handled for the last 15 years. Note that we keep the usedac option for now, as it is used in the wild to override the too generic VIA quirk. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
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@ -236,11 +236,6 @@ IOMMU (input/output memory management unit)
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nomerge Don't do scatter-gather (SG) merging.
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noaperture Ask the IOMMU not to touch the aperture for AGP.
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noagp Don't initialize the AGP driver and use full aperture.
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allowdac Allow double-address cycle (DAC) mode, i.e. DMA >4GB.
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DAC is used with 32-bit PCI to push a 64-bit address in
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two cycles. When off all DMA over >4GB is forced through
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an IOMMU or software bounce buffering.
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nodac Forbid DAC mode, i.e. DMA >4GB.
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panic Always panic when IOMMU overflows.
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calgary Use the Calgary IOMMU if it is available
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@ -122,9 +122,9 @@ static __init int iommu_setup(char *p)
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if (!strncmp(p, "forcesac", 8))
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pr_warn("forcesac option ignored.\n");
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if (!strncmp(p, "allowdac", 8))
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forbid_dac = 0;
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pr_warn("allowdac option ignored.\n");
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if (!strncmp(p, "nodac", 5))
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forbid_dac = 1;
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pr_warn("nodac option ignored.\n");
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if (!strncmp(p, "usedac", 6)) {
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forbid_dac = -1;
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return 1;
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