s390/cio: introduce bitwise dma types and helper functions

Introduce dma32_t and dma64_t bitwise types, which are supposed to be used
for 31 and 64 bit DMA capable addresses. This allows to use sparse (make
C=1) for type checking, so that incorrect usages can be easily found.

Also add a couple of helper functions which
- convert virtual to DMA addresses and vice versa
- allow for simple logical and arithmetic operations on DMA addresses
- convert DMA addresses to plain u32 and u64 values

All helper functions exist to avoid excessive casting in C code.

Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
Co-developed-by: Heiko Carstens <hca@linux.ibm.com>
Reviewed-by: Steffen Maier <maier@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

1 files changed, 103 insertions, 0 deletions

diff --git a/arch/s390/include/asm/dma-types.h b/arch/s390/include/asm/dma-types.h
new file mode 100644
index 000000000000..7d7f71022aa9
--- /dev/null
+++ b/arch/s390/include/asm/dma-types.h
@@ -0,0 +1,103 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+#ifndef _ASM_S390_DMA_TYPES_H_
+#define _ASM_S390_DMA_TYPES_H_
+
+#include <linux/types.h>
+#include <linux/io.h>
+
+/*
+ * typedef dma32_t
+ * Contains a 31 bit absolute address to a DMA capable piece of storage.
+ *
+ * For CIO, DMA addresses are always absolute addresses. These addresses tend
+ * to be used in architectured memory blocks (like ORB, IDAW, MIDAW). Under
+ * certain circumstances 31 bit wide addresses must be used because the
+ * address must fit in 31 bits.
+ *
+ * This type is to be used when such fields can be modelled as 32 bit wide.
+ */
+typedef u32 __bitwise dma32_t;
+
+/*
+ * typedef dma64_t
+ * Contains a 64 bit absolute address to a DMA capable piece of storage.
+ *
+ * For CIO, DMA addresses are always absolute addresses. These addresses tend
+ * to be used in architectured memory blocks (like ORB, IDAW, MIDAW).
+ *
+ * This type is to be used to model such 64 bit wide fields.
+ */
+typedef u64 __bitwise dma64_t;
+
+/*
+ * Although DMA addresses should be obtained using the DMA API, in cases when
+ * it is known that the first argument holds a virtual address that points to
+ * DMA-able 31 bit addressable storage, then this function can be safely used.
+ */
+static inline dma32_t virt_to_dma32(void *ptr)
+{
+	return (__force dma32_t)__pa(ptr);
+}
+
+static inline void *dma32_to_virt(dma32_t addr)
+{
+	return __va((__force unsigned long)addr);
+}
+
+static inline dma32_t u32_to_dma32(u32 addr)
+{
+	return (__force dma32_t)addr;
+}
+
+static inline u32 dma32_to_u32(dma32_t addr)
+{
+	return (__force u32)addr;
+}
+
+static inline dma32_t dma32_add(dma32_t a, u32 b)
+{
+	return (__force dma32_t)((__force u32)a + b);
+}
+
+static inline dma32_t dma32_and(dma32_t a, u32 b)
+{
+	return (__force dma32_t)((__force u32)a & b);
+}
+
+/*
+ * Although DMA addresses should be obtained using the DMA API, in cases when
+ * it is known that the first argument holds a virtual address that points to
+ * DMA-able storage, then this function can be safely used.
+ */
+static inline dma64_t virt_to_dma64(void *ptr)
+{
+	return (__force dma64_t)__pa(ptr);
+}
+
+static inline void *dma64_to_virt(dma64_t addr)
+{
+	return __va((__force unsigned long)addr);
+}
+
+static inline dma64_t u64_to_dma64(u64 addr)
+{
+	return (__force dma64_t)addr;
+}
+
+static inline u64 dma64_to_u64(dma64_t addr)
+{
+	return (__force u64)addr;
+}
+
+static inline dma64_t dma64_add(dma64_t a, u64 b)
+{
+	return (__force dma64_t)((__force u64)a + b);
+}
+
+static inline dma64_t dma64_and(dma64_t a, u64 b)
+{
+	return (__force dma64_t)((__force u64)a & b);
+}
+
+#endif /* _ASM_S390_DMA_TYPES_H_ */