[PATCH 1/1] powerpc/kernel/iommu: Use largepool as a last resort when !largealloc

[Leonardo Bras]

As of today, doing iommu_range_alloc() only for !largealloc (npages <= 15)
will only be able to use 3/4 of the available pages, given pages on
largepool  not being available for !largealloc.

This could mean some drivers not being able to fully use all the available
pages for the DMA window.

Add pages on largepool as a last resort for !largealloc, making all pages
of the DMA window available.

Signed-off-by: Leonardo Bras <leobras.c at gmail.com>
Reviewed-by: Alexey Kardashevskiy <aik at ozlabs.ru>
---
 arch/powerpc/kernel/iommu.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/powerpc/kernel/iommu.c b/arch/powerpc/kernel/iommu.c
index 3329ef045805..ae6ad8dca605 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -255,6 +255,15 @@ static unsigned long iommu_range_alloc(struct device *dev,
 			pass++;
 			goto again;
 
+		} else if (pass == tbl->nr_pools + 1) {
+			/* Last resort: try largepool */
+			spin_unlock(&pool->lock);
+			pool = &tbl->large_pool;
+			spin_lock(&pool->lock);
+			pool->hint = pool->start;
+			pass++;
+			goto again;
+
 		} else {
 			/* Give up */
 			spin_unlock_irqrestore(&(pool->lock), flags);
-- 
2.29.2