[PATCH RFC v1 3/6] swiotlb: introduce swiotlb_get_type() to calculate swiotlb buffer type

Dongli Zhang
2021-02-03T23:40:41Z

This patch introduces swiotlb_get_type() in order to calculate which
swiotlb buffer the given DMA address is belong to.

This is to prepare to enable 64-bit swiotlb.

Cc: Joe Jin <joe.jin@oracle.com>
Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
---
include/linux/swiotlb.h | 14 ++++++++++++++
kernel/dma/swiotlb.c | 2 ++
2 files changed, 16 insertions(+)

diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
index 777046cd4d1b..3d5980d77810 100644
--- a/include/linux/swiotlb.h
+++ b/include/linux/swiotlb.h
@@ -3,6 +3,7 @@
#define __LINUX_SWIOTLB_H

#include <linux/dma-direction.h>
+#include <linux/errno.h>
#include <linux/init.h>
#include <linux/types.h>
#include <linux/limits.h>
@@ -23,6 +24,8 @@ enum swiotlb_t {
SWIOTLB_MAX,
};

+extern int swiotlb_nr;
+
/*
* Maximum allowable number of contiguous slabs to map,
* must be a power of 2. What is the appropriate value ?
@@ -84,6 +87,17 @@ static inline bool is_swiotlb_buffer(phys_addr_t paddr)
paddr < io_tlb_end[SWIOTLB_LO];
}

+static inline int swiotlb_get_type(phys_addr_t paddr)
+{
+ int i;
+
+ for (i = 0; i < swiotlb_nr; i++)
+ if (paddr >= io_tlb_start[i] && paddr < io_tlb_end[i])
+ return i;
+
+ return -ENOENT;
+}
+
void __init swiotlb_exit(void);
unsigned int swiotlb_max_segment(void);
size_t swiotlb_max_mapping_size(struct device *dev);
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 1fbb65daa2dd..c91d3d2c3936 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -109,6 +109,8 @@ static DEFINE_SPINLOCK(io_tlb_lock);

static int late_alloc;

+int swiotlb_nr = 1;
+
static int __init
setup_io_tlb_npages(char *str)
{
--
2.17.1