[PATCH v1 03/10] powerpc/kernel/iommu: Use largepool as a last resort when !largealloc

Leonardo Bras
2020-08-17T23:41:12Z

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@gmail.com>
---
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 d7086087830f..7f603d4e62d4 100644
--- a/arch/powerpc/kernel/iommu.c
+++ b/arch/powerpc/kernel/iommu.c
@@ -261,6 +261,15 @@ 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);
--
2.25.4