Fix use of MSR (immediate)

The macro DEFINE_SYSREG_WRITE_CONST_FUNC defines an inline function
to an assembly statement that uses the MSR (immediate) instruction
to access the PSTATE.  The "i" (immediate) assembly constraint on
the operand was only satisfied when compiling with optimizations
enabled which resulted in the function being optimized out - the
"const uint64_t v" parameter was optimized out and replaced by a
literal value.

When compiling without optimizations, the function call remained and
therefore the parameter is not optimized out - compilation fails as
the constraint is impossible to satisfy by the compiler.

This patch replaces the function encapsulating the use of
the MSR (immediate) with a macro that allows the literal value to be
directly fed to the inline assembly statement

Change-Id: Ib379a7acc48ef3cb83090a680cd8a6ce1a94a9d9
Signed-off-by: Roberto Vargas <roberto.vargas@arm.com>

include/lib/aarch64/arch_helpers.h

@@ -31,11 +31,8 @@ static inline void write_ ## _name(uint64_t v)				\
 	__asm__ volatile ("msr " #_reg_name ", %0" : : "r" (v));	\
 }
 
-#define _DEFINE_SYSREG_WRITE_CONST_FUNC(_name, _reg_name)		\
-static inline void write_ ## _name(const uint64_t v)			\
-{									\
-	__asm__ volatile ("msr " #_reg_name ", %0" : : "i" (v));	\
-}
+#define SYSREG_WRITE_CONST(reg_name, v)				\
+	__asm__ volatile ("msr " #reg_name ", %0" : : "i" (v))
 
 /* Define read function for system register */
 #define DEFINE_SYSREG_READ_FUNC(_name) 			\
@@ -59,11 +56,6 @@ static inline void write_ ## _name(const uint64_t v)			\
 #define DEFINE_RENAME_SYSREG_WRITE_FUNC(_name, _reg_name)	\
 	_DEFINE_SYSREG_WRITE_FUNC(_name, _reg_name)
 
-/* Define write function for special system registers */
-#define DEFINE_SYSREG_WRITE_CONST_FUNC(_name)		\
-	_DEFINE_SYSREG_WRITE_CONST_FUNC(_name, _name)
-
-
 /**********************************************************************
  * Macros to create inline functions for system instructions
  *********************************************************************/
@@ -178,8 +170,8 @@ void disable_mmu_icache_el3(void);
  * Misc. accessor prototypes
  ******************************************************************************/
 
-DEFINE_SYSREG_WRITE_CONST_FUNC(daifset)
-DEFINE_SYSREG_WRITE_CONST_FUNC(daifclr)
+#define write_daifclr(val) SYSREG_WRITE_CONST(daifclr, val)
+#define write_daifset(val) SYSREG_WRITE_CONST(daifset, val)
 
 DEFINE_SYSREG_READ_FUNC(par_el1)
 DEFINE_SYSREG_READ_FUNC(id_pfr1_el1)