[PATCH] powerpc: convert 'iommu_alloc failed' messages to dynamic debug

[Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com>]

This prevents flooding the logs with 'iommu_alloc failed' messages
while I/O is performed (normally) to very fast devices (e.g. NVMe).

That error is not necessarily a problem; device drivers can retry
later / reschedule the requests for which the allocation failed,
and handle things gracefully for the caller stack on top of them.

This helps at least with NVMe devices without "64-bit"/direct DMA
window scenarios (e.g., systems with more than a few terabytes of
memory, on which DDW cannot be enabled, currently), where just an
'dd' command can trigger errors.

  # dd if=/dev/zero of=/dev/nvme0n1p1 bs=64k count=512k
  <...>
  # echo $?
  0

  # dmesg
  nvme 0000:00:06.0: iommu_alloc failed, tbl c0000001fa67c520 vaddr c000000151c90000 npages 16
  nvme 0000:00:06.0: iommu_alloc failed, tbl c0000001fa67c520 vaddr c000000151c90000 npages 16
  nvme 0000:00:06.0: iommu_alloc failed, tbl c0000001fa67c520 vaddr c000000151c90000 npages 16
  <...>
  ppc_iommu_map_sg: 8186 callbacks suppressed
  nvme 0000:00:06.0: iommu_alloc failed, tbl c0000001fa67c520 vaddr c0000000fa5c0000 npages 16
  nvme 0000:00:06.0: iommu_alloc failed, tbl c0000001fa67c520 vaddr c000000100440000 npages 16
  nvme 0000:00:06.0: iommu_alloc failed, tbl c0000001fa67c520 vaddr c000000100440000 npages 16
  <...>
  ppc_iommu_map_sg: 5707 callbacks suppressed
  nvme 0000:00:06.0: iommu_alloc failed, tbl c0000001fa67c520 vaddr c0000000b5f50000 npages 16
  nvme 0000:00:06.0: iommu_alloc failed, tbl c0000001fa67c520 vaddr c0000000b5c60000 npages 16
  nvme 0000:00:06.0: iommu_alloc failed, tbl c0000001fa67c520 vaddr c0000000b4b30000 npages 16
  <...>

Tested on next-20160609.

Signed-off-by: Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com>
---
 arch/powerpc/kernel/iommu.c | 15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index a8e3490..b585bdc 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -479,10 +479,9 @@ int ppc_iommu_map_sg(struct device *dev, struct iommu_table *tbl,
 
 		/* Handle failure */
 		if (unlikely(entry == DMA_ERROR_CODE)) {
-			if (printk_ratelimit())
-				dev_info(dev, "iommu_alloc failed, tbl %p "
-					 "vaddr %lx npages %lu\n", tbl, vaddr,
-					 npages);
+			dev_dbg_ratelimited(dev, "iommu_alloc failed, tbl %p "
+				 "vaddr %lx npages %lu\n", tbl, vaddr,
+				 npages);
 			goto failure;
 		}
 
@@ -776,11 +775,9 @@ dma_addr_t iommu_map_page(struct device *dev, struct iommu_table *tbl,
 					 mask >> tbl->it_page_shift, align,
 					 attrs);
 		if (dma_handle == DMA_ERROR_CODE) {
-			if (printk_ratelimit())  {
-				dev_info(dev, "iommu_alloc failed, tbl %p "
-					 "vaddr %p npages %d\n", tbl, vaddr,
-					 npages);
-			}
+			dev_dbg_ratelimited(dev, "iommu_alloc failed, tbl %p "
+				 "vaddr %p npages %d\n", tbl, vaddr,
+				 npages);
 		} else
 			dma_handle |= (uaddr & ~IOMMU_PAGE_MASK(tbl));
 	}
-- 
1.8.3.1