iosys-map: Add per-word write

Like was done for read, provide the equivalent for write. Even if
current users are not in the hot path, this should future-proof it.

v2:
  - Remove default from _Generic() - callers wanting to write more
    than u64 should use iosys_map_memcpy_to()
  - Add WRITE_ONCE() cases dereferencing the pointer when using system
    memory
v3:
  - Fix precedence issue when casting inside WRITE_ONCE(). By not using ()
    around vaddr__ the offset was not part of the cast, but rather added
    to it, producing a wrong address
  - Remove compiletime_assert() as WRITE_ONCE() already contains it

Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Reviewed-by: Christian König <christian.koenig@amd.com> # v1
Reviewed-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20220628191016.3899428-2-lucas.demarchi@intel.com

include/linux/iosys-map.h

@@ -337,9 +337,13 @@ static inline void iosys_map_memset(struct iosys_map *dst, size_t offset,
 #ifdef CONFIG_64BIT
 #define __iosys_map_rd_io_u64_case(val_, vaddr_iomem_)				\
 	u64: val_ = readq(vaddr_iomem_)
+#define __iosys_map_wr_io_u64_case(val_, vaddr_iomem_)				\
+	u64: writeq(val_, vaddr_iomem_)
 #else
 #define __iosys_map_rd_io_u64_case(val_, vaddr_iomem_)				\
 	u64: memcpy_fromio(&(val_), vaddr_iomem_, sizeof(u64))
+#define __iosys_map_wr_io_u64_case(val_, vaddr_iomem_)				\
+	u64: memcpy_toio(vaddr_iomem_, &(val_), sizeof(u64))
 #endif
 
 #define __iosys_map_rd_io(val__, vaddr_iomem__, type__) _Generic(val__,		\
@@ -351,6 +355,15 @@ static inline void iosys_map_memset(struct iosys_map *dst, size_t offset,
 #define __iosys_map_rd_sys(val__, vaddr__, type__)				\
 	val__ = READ_ONCE(*(type__ *)(vaddr__))
 
+#define __iosys_map_wr_io(val__, vaddr_iomem__, type__) _Generic(val__,		\
+	u8: writeb(val__, vaddr_iomem__),					\
+	u16: writew(val__, vaddr_iomem__),					\
+	u32: writel(val__, vaddr_iomem__),					\
+	__iosys_map_wr_io_u64_case(val__, vaddr_iomem__))
+
+#define __iosys_map_wr_sys(val__, vaddr__, type__)				\
+	WRITE_ONCE(*(type__ *)(vaddr__), val__)
+
 /**
  * iosys_map_rd - Read a C-type value from the iosys_map
  *
@@ -383,12 +396,17 @@ static inline void iosys_map_memset(struct iosys_map *dst, size_t offset,
  * @type__:	Type of the value being written
  * @val__:	Value to write
  *
- * Write a C-type value to the iosys_map, handling possible un-aligned accesses
- * to the mapping.
+ * Write a C type value (u8, u16, u32 and u64) to the iosys_map. For other types
+ * or if pointer may be unaligned (and problematic for the architecture
+ * supported), use iosys_map_memcpy_to()
  */
-#define iosys_map_wr(map__, offset__, type__, val__) ({			\
-	type__ val = (val__);						\
-	iosys_map_memcpy_to(map__, offset__, &val, sizeof(val));	\
+#define iosys_map_wr(map__, offset__, type__, val__) ({				\
+	type__ val = (val__);							\
+	if ((map__)->is_iomem) {						\
+		__iosys_map_wr_io(val, (map__)->vaddr_iomem + (offset__), type__);\
+	} else {								\
+		__iosys_map_wr_sys(val, (map__)->vaddr + (offset__), type__);	\
+	}									\
 })
 
 /**
@@ -469,10 +487,12 @@ static inline void iosys_map_memset(struct iosys_map *dst, size_t offset,
  * @field__:		Member of the struct to read
  * @val__:		Value to write
  *
- * Write a value to the iosys_map considering its layout is described by a C struct
- * starting at @struct_offset__. The field offset and size is calculated and the
- * @val__ is written handling possible un-aligned memory accesses. Refer to
- * iosys_map_rd_field() for expected usage and memory layout.
+ * Write a value to the iosys_map considering its layout is described by a C
+ * struct starting at @struct_offset__. The field offset and size is calculated
+ * and the @val__ is written. If the field access would incur in un-aligned
+ * access, then either iosys_map_memcpy_to() needs to be used or the
+ * architecture must support it. Refer to iosys_map_rd_field() for expected
+ * usage and memory layout.
  */
 #define iosys_map_wr_field(map__, struct_offset__, struct_type__, field__, val__) ({	\
 	struct_type__ *s;								\