diff mbox series

[kernel,v5,2/4] powerpc/iommu: Allow bypass-only for DMA

Message ID 20190718051139.74787-3-aik@ozlabs.ru
State Accepted
Commit 4f7e0babbc7c46fc0db4f5c14fe96bf6f4d69502
Headers show
Series powerpc/ioda2: Yet another attempt to allow DMA masks between 32 and 59 | expand


Context Check Description
snowpatch_ozlabs/checkpatch warning total: 0 errors, 1 warnings, 0 checks, 23 lines checked
snowpatch_ozlabs/apply_patch success Successfully applied on branch next (f5c20693d8edcd665f1159dc941b9e7f87c17647)

Commit Message

Alexey Kardashevskiy July 18, 2019, 5:11 a.m. UTC
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 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 mbox series


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",