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authorAlistair Popple <alistair@popple.id.au>2017-07-26 15:26:40 +1000
committerMichael Ellerman <mpe@ellerman.id.au>2017-07-28 23:02:55 +1000
commit253fd51e2f533552ae35a0c661705da6c4842c1b (patch)
tree7165717bcfc44642ddf21a3fd5afa7877fb59840 /arch/powerpc/platforms/powernv
parent65c5ec11c25eff6ba6e9b1cbfff014875fddd1e0 (diff)
powerpc/powernv/pci: Return failure for some uses of dma_set_mask()
Commit 8e3f1b1d8255 ("powerpc/powernv/pci: Enable 64-bit devices to access >4GB DMA space") introduced the ability for PCI device drivers to request a DMA mask between 64 and 32 bits and actually get a mask greater than 32-bits. However currently if certain machine configuration dependent conditions are not meet the code silently falls back to a 32-bit mask. This makes it hard for device drivers to detect which mask they actually got. Instead we should return an error when the request could not be fulfilled which allows drivers to either fallback or implement other workarounds as documented in DMA-API-HOWTO.txt. Signed-off-by: Alistair Popple <alistair@popple.id.au> Acked-by: Russell Currey <ruscur@russell.cc> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Diffstat (limited to 'arch/powerpc/platforms/powernv')
-rw-r--r--arch/powerpc/platforms/powernv/pci-ioda.c8
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/powerpc/platforms/powernv/pci-ioda.c b/arch/powerpc/platforms/powernv/pci-ioda.c
index 437613588df1..b900eb1d5e17 100644
--- a/arch/powerpc/platforms/powernv/pci-ioda.c
+++ b/arch/powerpc/platforms/powernv/pci-ioda.c
@@ -1852,6 +1852,14 @@ static int pnv_pci_ioda_dma_set_mask(struct pci_dev *pdev, u64 dma_mask)
/* 4GB offset bypasses 32-bit space */
set_dma_offset(&pdev->dev, (1ULL << 32));
set_dma_ops(&pdev->dev, &dma_direct_ops);
+ } else if (dma_mask >> 32 && dma_mask != DMA_BIT_MASK(64)) {
+ /*
+ * Fail the request if a DMA mask between 32 and 64 bits
+ * was requested but couldn't be fulfilled. Ideally we
+ * would do this for 64-bits but historically we have
+ * always fallen back to 32-bits.
+ */
+ return -ENOMEM;
} else {
dev_info(&pdev->dev, "Using 32-bit DMA via iommu\n");
set_dma_ops(&pdev->dev, &dma_iommu_ops);