dma-debug: add Kconfig entry

Impact: add a Kconfig entry for DMA-API debugging

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>

arch/Kconfig

@@ -106,3 +106,5 @@ config HAVE_CLK
 	  The <linux/clk.h> calls support software clock gating and
 	  thus are a key power management tool on many systems.
 
+config HAVE_DMA_API_DEBUG
+	bool

lib/Kconfig.debug

@@ -902,6 +902,17 @@ config DYNAMIC_PRINTK_DEBUG
 	  debugging for all modules. This mode can be turned off via the above
 	  disable command.
 
+config DMA_API_DEBUG
+	bool "Enable debugging of DMA-API usage"
+	depends on HAVE_DMA_API_DEBUG
+	help
+	  Enable this option to debug the use of the DMA API by device drivers.
+	  With this option you will be able to detect common bugs in device
+	  drivers like double-freeing of DMA mappings or freeing mappings that
+	  were never allocated.
+	  This option causes a performance degredation.  Use only if you want
+	  to debug device drivers. If unsure, say N.
+
 source "samples/Kconfig"
 
 source "lib/Kconfig.kgdb"