[PATCH] [v2] arm64/io: add constant-argument check

[Arnd Bergmann]

From: Arnd Bergmann <arnd@xxxxxxxx>

In some configurations __const_iowrite32_copy() does not get inlined
and gcc runs into the BUILD_BUG():

In file included from <command-line>:
In function '__const_memcpy_toio_aligned32',
    inlined from '__const_iowrite32_copy' at arch/arm64/include/asm/io.h:203:3,
    inlined from '__const_iowrite32_copy' at arch/arm64/include/asm/io.h:199:20:
include/linux/compiler_types.h:487:45: error: call to '__compiletime_assert_538' declared with attribute error: BUILD_BUG failed
  487 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
      |                                             ^
include/linux/compiler_types.h:468:25: note: in definition of macro '__compiletime_assert'
  468 |                         prefix ## suffix();                             \
      |                         ^~~~~~
include/linux/compiler_types.h:487:9: note: in expansion of macro '_compiletime_assert'
  487 |         _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
      |         ^~~~~~~~~~~~~~~~~~~
include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
   39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
      |                                     ^~~~~~~~~~~~~~~~~~
include/linux/build_bug.h:59:21: note: in expansion of macro 'BUILD_BUG_ON_MSG'
   59 | #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
      |                     ^~~~~~~~~~~~~~~~
arch/arm64/include/asm/io.h:193:17: note: in expansion of macro 'BUILD_BUG'
  193 |                 BUILD_BUG();
      |                 ^~~~~~~~~

Move the check for constant arguments into the inline function to ensure
it is still constant if the compiler decides against inlining it.

Fixes: ead79118dae6 ("arm64/io: Provide a WC friendly __iowriteXX_copy()")
Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
---
v2:
 - fix both 32-bit and 64-bit copies
 - remove now-redundant macros
---
 arch/arm64/include/asm/io.h | 24 +++++++++---------------
 1 file changed, 9 insertions(+), 15 deletions(-)

diff --git a/arch/arm64/include/asm/io.h b/arch/arm64/include/asm/io.h
index 4ff0ae3f6d66..902026f81b97 100644
--- a/arch/arm64/include/asm/io.h
+++ b/arch/arm64/include/asm/io.h
@@ -196,21 +196,18 @@ static inline void __const_memcpy_toio_aligned32(volatile u32 __iomem *to,
 
 void __iowrite32_copy_full(void __iomem *to, const void *from, size_t count);
 
-static inline void __const_iowrite32_copy(void __iomem *to, const void *from,
-					  size_t count)
+static inline void __iowrite32_copy(void __iomem *to, const void *from,
+				    size_t count)
 {
-	if (count == 8 || count == 4 || count == 2 || count == 1) {
+	if (__builtin_constant_p(count) &&
+	    (count == 8 || count == 4 || count == 2 || count == 1)) {
 		__const_memcpy_toio_aligned32(to, from, count);
 		dgh();
 	} else {
 		__iowrite32_copy_full(to, from, count);
 	}
 }
-
-#define __iowrite32_copy(to, from, count)                  \
-	(__builtin_constant_p(count) ?                     \
-		 __const_iowrite32_copy(to, from, count) : \
-		 __iowrite32_copy_full(to, from, count))
+#define __iowrite32_copy(to, from, count) __iowrite32_copy(to, from, count)
 
 static inline void __const_memcpy_toio_aligned64(volatile u64 __iomem *to,
 						 const u64 *from, size_t count)
@@ -255,21 +252,18 @@ static inline void __const_memcpy_toio_aligned64(volatile u64 __iomem *to,
 
 void __iowrite64_copy_full(void __iomem *to, const void *from, size_t count);
 
-static inline void __const_iowrite64_copy(void __iomem *to, const void *from,
+static inline void __iowrite64_copy(void __iomem *to, const void *from,
 					  size_t count)
 {
-	if (count == 8 || count == 4 || count == 2 || count == 1) {
+	if (__builtin_constant_p(count) &&
+	    (count == 8 || count == 4 || count == 2 || count == 1)) {
 		__const_memcpy_toio_aligned64(to, from, count);
 		dgh();
 	} else {
 		__iowrite64_copy_full(to, from, count);
 	}
 }
-
-#define __iowrite64_copy(to, from, count)                  \
-	(__builtin_constant_p(count) ?                     \
-		 __const_iowrite64_copy(to, from, count) : \
-		 __iowrite64_copy_full(to, from, count))
+#define __iowrite64_copy(to, from, count) __iowrite64_copy(to, from, count)
 
 /*
  * I/O memory mapping functions.
-- 
2.39.2