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Subject[PATCH kernel v4 2/4] powerpc/iommu: Allow bypass-only for DMA
Date
POWER8 and newer support a bypass mode which maps all host memory to
PCI buses so an IOMMU table is not always required. However if we fail to
create such a table, the DMA setup fails and the kernel does not boot.

This skips the 32bit DMA setup check if the bypass is can be selected.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
---

This minor thing helped me debugging next 2 patches so it can help
somebody else too.
---
arch/powerpc/kernel/dma-iommu.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/arch/powerpc/kernel/dma-iommu.c b/arch/powerpc/kernel/dma-iommu.c
index a0879674a9c8..c963d704fa31 100644
--- a/arch/powerpc/kernel/dma-iommu.c
+++ b/arch/powerpc/kernel/dma-iommu.c
@@ -122,18 +122,17 @@ int dma_iommu_dma_supported(struct device *dev, u64 mask)
{
struct iommu_table *tbl = get_iommu_table_base(dev);

- if (!tbl) {
- dev_info(dev, "Warning: IOMMU dma not supported: mask 0x%08llx"
- ", table unavailable\n", mask);
- return 0;
- }
-
if (dev_is_pci(dev) && dma_iommu_bypass_supported(dev, mask)) {
dev->archdata.iommu_bypass = true;
dev_dbg(dev, "iommu: 64-bit OK, using fixed ops\n");
return 1;
}

+ if (!tbl) {
+ dev_err(dev, "Warning: IOMMU dma not supported: mask 0x%08llx, table unavailable\n", mask);
+ return 0;
+ }
+
if (tbl->it_offset > (mask >> tbl->it_page_shift)) {
dev_info(dev, "Warning: IOMMU offset too big for device mask\n");
dev_info(dev, "mask: 0x%08llx, table offset: 0x%08lx\n",
--
2.17.1
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