[PATCH v7 8/8] swiotlb: Make IO_TLB_SEGSIZE configurable

[huaqian.li at siemens.com]

From: Li Hua Qian <huaqian.li at siemens.com>

In some applications, the default value of 128 is not sufficient for
memory allocation and can cause runtime errors. This change makes
IO_TLB_SEGSIZE configurable, allowing it to be increased if needed.

Signed-off-by: Li Hua Qian <huaqian.li at siemens.com>
---
 include/linux/swiotlb.h | 2 +-
 kernel/dma/Kconfig      | 7 +++++++
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index 3dae0f592063..145c71f8329d 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -23,7 +23,7 @@ struct scatterlist;
  * must be a power of 2.  What is the appropriate value ?
  * The complexity of {map,unmap}_single is linearly dependent on this value.
  */
-#define IO_TLB_SEGSIZE	128
+#define IO_TLB_SEGSIZE CONFIG_SWIOTLB_SEGSIZE
 
 /*
  * log of the size of each IO TLB slab.  The number of slabs is command line
diff --git a/kernel/dma/Kconfig b/kernel/dma/Kconfig
index 31cfdb6b4bc3..38bfa84b96b6 100644
--- a/kernel/dma/Kconfig
+++ b/kernel/dma/Kconfig
@@ -102,6 +102,13 @@ config SWIOTLB_DYNAMIC
 
 	  If unsure, say N.
 
+config SWIOTLB_SEGSIZE
+	int "SWIOTLB segment size"
+	default 128
+	help
+	  Set the maximum allowable number of contiguous slabs to map.
+	  Must be a power of 2.
+
 config DMA_BOUNCE_UNALIGNED_KMALLOC
 	bool
 	depends on SWIOTLB
-- 
2.34.1