[PATCH] dma-debug: Kconfig for PREALLOC_DMA_DEBUG_ENTRIES

[Qian Cai]

The amount of DMA mappings from Hisilicon HNS ethernet devices is huge,
so it could trigger "DMA-API: debugging out of memory - disabling".

hnae_get_handle [1]
  hnae_init_queue
    hnae_init_ring
      hnae_alloc_buffers [2]
        debug_dma_map_page
          dma_entry_alloc

[1] for (i = 0; i < handle->q_num; i++)
[2] for (i = 0; i < ring->desc_num; i++)

On this Huawei TaiShan 2280 aarch64 server, it has reached the limit
already,

4 (ports) x 16 (handles) x 1024 (rings) = 65536

Added a Kconfig entry for PREALLOC_DMA_DEBUG_ENTRIES, so make it easier
for users to deal with special cases like this.

Signed-off-by: Qian Cai <c...@gmx.us>
---
 kernel/dma/debug.c | 9 ++-------
 lib/Kconfig.debug  | 9 +++++++++
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index 231ca4628062..3752fb23f72f 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -41,11 +41,6 @@
 #define HASH_FN_SHIFT   13
 #define HASH_FN_MASK    (HASH_SIZE - 1)
 
-/* allow architectures to override this if absolutely required */
-#ifndef PREALLOC_DMA_DEBUG_ENTRIES
-#define PREALLOC_DMA_DEBUG_ENTRIES (1 << 16)
-#endif
-
 enum {
        dma_debug_single,
        dma_debug_page,
@@ -132,7 +127,7 @@ static u32 min_free_entries;
 static u32 nr_total_entries;
 
 /* number of preallocated entries requested by kernel cmdline */
-static u32 nr_prealloc_entries = PREALLOC_DMA_DEBUG_ENTRIES;
+static u32 nr_prealloc_entries = CONFIG_PREALLOC_DMA_DEBUG_ENTRIES;
 
 /* debugfs dentry's for the stuff above */
 static struct dentry *dma_debug_dent        __read_mostly;
@@ -1063,7 +1058,7 @@ static __init int dma_debug_entries_cmdline(char *str)
        if (!str)
                return -EINVAL;
        if (!get_option(&str, &nr_prealloc_entries))
-               nr_prealloc_entries = PREALLOC_DMA_DEBUG_ENTRIES;
+               nr_prealloc_entries = CONFIG_PREALLOC_DMA_DEBUG_ENTRIES;
        return 0;
 }
 
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 1af29b8224fd..2c281edcb5ad 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1659,6 +1659,15 @@ config DMA_API_DEBUG
 
          If unsure, say N.
 
+config PREALLOC_DMA_DEBUG_ENTRIES
+       int "Preallocated DMA-API debugging entries"
+       depends on DMA_API_DEBUG
+       default 65536
+       help
+         The number of preallocated entries for DMA-API debugging code. One
+         entry is required per DMA-API allocation. Increase this if the DMA-API
+         debugging code disables itself because the default is too low.
+
 config DMA_API_DEBUG_SG
        bool "Debug DMA scatter-gather usage"
        default y
-- 
2.17.2 (Apple Git-113)