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Subject[PATCH 3/4] dma-pool: Introduce dma_guess_pool()
Date
dma-pool's dev_to_pool() creates the false impression that there is a
way to grantee a mapping between a device's DMA constraints and an
atomic pool. It tuns out it's just a guess, and the device might need to
use an atomic pool containing memory from a 'safer' (or lower) memory
zone.

To help mitigate this, introduce dma_guess_pool() which can be fed a
device's DMA constraints or an atomic pool already known to be faulty in
order for it to provide a better guess at which pool to use.

Signed-off-by: Nicolas Saenz Julienne <nsaenzjulienne@suse.de>
---
kernel/dma/pool.c | 26 +++++++++++++++++++++++---
1 file changed, 23 insertions(+), 3 deletions(-)

diff --git a/kernel/dma/pool.c b/kernel/dma/pool.c
index 7363640fc91c..3d518de07617 100644
--- a/kernel/dma/pool.c
+++ b/kernel/dma/pool.c
@@ -203,7 +203,7 @@ static int __init dma_atomic_pool_init(void)
}
postcore_initcall(dma_atomic_pool_init);

-static inline struct gen_pool *dev_to_pool(struct device *dev)
+static inline struct gen_pool *dma_guess_pool_from_device(struct device *dev)
{
u64 phys_mask;
gfp_t gfp;
@@ -217,10 +217,30 @@ static inline struct gen_pool *dev_to_pool(struct device *dev)
return atomic_pool_kernel;
}

+static inline struct gen_pool *dma_get_safer_pool(struct gen_pool *bad_pool)
+{
+ if (bad_pool == atomic_pool_kernel)
+ return atomic_pool_dma32 ? : atomic_pool_dma;
+
+ if (bad_pool == atomic_pool_dma32)
+ return atomic_pool_dma;
+
+ return NULL;
+}
+
+static inline struct gen_pool *dma_guess_pool(struct device *dev,
+ struct gen_pool *bad_pool)
+{
+ if (bad_pool)
+ return dma_get_safer_pool(bad_pool);
+
+ return dma_guess_pool_from_device(dev);
+}
+
void *dma_alloc_from_pool(struct device *dev, size_t size,
struct page **ret_page, gfp_t flags)
{
- struct gen_pool *pool = dev_to_pool(dev);
+ struct gen_pool *pool = dma_guess_pool(dev, NULL);
unsigned long val;
void *ptr = NULL;

@@ -245,7 +265,7 @@ void *dma_alloc_from_pool(struct device *dev, size_t size,

bool dma_free_from_pool(struct device *dev, void *start, size_t size)
{
- struct gen_pool *pool = dev_to_pool(dev);
+ struct gen_pool *pool = dma_guess_pool(dev, NULL);

if (!pool || !gen_pool_has_addr(pool, (unsigned long)start, size))
return false;
--
2.27.0
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