Re: [PATCH 03/10] x86: add initialization code for DMA-API debugging

On Sat, Nov 22, 2008 at 12:27:41PM +0900, FUJITA Tomonori wrote:

On Fri, 21 Nov 2008 17:26:03 +0100
Joerg Roedel [off-list ref] wrote:

quoted

Impact: creates necessary data structures for DMA-API debugging

Signed-off-by: Joerg Roedel <redacted>
---
 arch/x86/include/asm/dma-mapping.h |    1 +
 arch/x86/include/asm/dma_debug.h   |   14 +++++
 arch/x86/kernel/Makefile           |    2 +
 arch/x86/kernel/pci-dma-debug.c    |  111 ++++++++++++++++++++++++++++++++++++
 arch/x86/kernel/pci-dma.c          |    2 +
 5 files changed, 130 insertions(+), 0 deletions(-)
 create mode 100644 arch/x86/kernel/pci-dma-debug.c

diff --git a/arch/x86/include/asm/dma-mapping.h b/arch/x86/include/asm/dma-mapping.h
index 7f225a4..83d7b7d 100644
--- a/arch/x86/include/asm/dma-mapping.h
+++ b/arch/x86/include/asm/dma-mapping.h

@@ -9,6 +9,7 @@
 #include <linux/scatterlist.h>
 #include <asm/io.h>
 #include <asm/swiotlb.h>
+#include <asm/dma_debug.h>
 #include <asm-generic/dma-coherent.h>
 
 extern dma_addr_t bad_dma_address;

diff --git a/arch/x86/include/asm/dma_debug.h b/arch/x86/include/asm/dma_debug.h
index d79f024..f2c3d53 100644
--- a/arch/x86/include/asm/dma_debug.h
+++ b/arch/x86/include/asm/dma_debug.h

@@ -38,4 +38,18 @@ struct dma_debug_entry {
 	int direction;
 };
 
+#ifdef CONFIG_DMA_API_DEBUG
+
+extern
+void dma_debug_init(void);
+
+#else /* CONFIG_DMA_API_DEBUG */
+
+static inline
+void dma_debug_init(void)
+{
+}
+
+#endif /* CONFIG_DMA_API_DEBUG */
+
 #endif /* __ASM_X86_DMA_DEBUG */

diff --git a/arch/x86/kernel/Makefile b/arch/x86/kernel/Makefile
index e489ff9..6271cd2 100644
--- a/arch/x86/kernel/Makefile
+++ b/arch/x86/kernel/Makefile

@@ -105,6 +105,8 @@ microcode-$(CONFIG_MICROCODE_INTEL)	+= microcode_intel.o
 microcode-$(CONFIG_MICROCODE_AMD)	+= microcode_amd.o
 obj-$(CONFIG_MICROCODE)			+= microcode.o
 
+obj-$(CONFIG_DMA_API_DEBUG)             += pci-dma-debug.o
+
 ###
 # 64 bit specific files
 ifeq ($(CONFIG_X86_64),y)

diff --git a/arch/x86/kernel/pci-dma-debug.c b/arch/x86/kernel/pci-dma-debug.c
new file mode 100644
index 0000000..c2d3408
--- /dev/null
+++ b/arch/x86/kernel/pci-dma-debug.c

@@ -0,0 +1,111 @@
+/*
+ * Copyright (C) 2008 Advanced Micro Devices, Inc.
+ *
+ * Author: Joerg Roedel <joerg.roedel@amd.com>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published
+ * by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307 USA
+ */
+
+#include <linux/types.h>
+#include <linux/scatterlist.h>
+#include <linux/list.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/module.h>
+#include <linux/hardirq.h>
+#include <linux/dma-mapping.h>
+#include <asm/bug.h>
+#include <asm/dma-mapping.h>
+#include <asm/dma_debug.h>
+
+#define HASH_SIZE 256
+#define HASH_FN_SHIFT 20
+#define HASH_FN_MASK 0xffULL
+
+/* Hash list to save the allocated dma addresses */
+static struct list_head dma_entry_hash[HASH_SIZE];
+
+/* A slab cache to allocate dma_map_entries fast */
+static struct kmem_cache *dma_entry_cache;
+
+/* lock to protect the data structures */
+static DEFINE_SPINLOCK(dma_lock);
+
+static int hash_fn(struct dma_debug_entry *entry)
+{
+	/*
+	 * Hash function is based on the dma address.
+	 * We use bits 20-27 here as the index into the hash
+	 */
+	BUG_ON(entry->dev_addr == bad_dma_address);

'bad_dma_address' is x86 specific. You already found it though.

Interesting. Is there another value for dma_addr_t which drivers can
check for to find out if a dma-api operation failed?

Joerg