From: Michael Ellerman mpe@ellerman.id.au
[ Upstream commit eead089311f4d935ab5d1d8fbb0c42ad44699ada ]
lkp reported a build error in fsp2.o:
CC arch/powerpc/platforms/44x/fsp2.o {standard input}:577: Error: unsupported relocation against base
Which comes from:
pr_err("GESR0: 0x%08x\n", mfdcr(base + PLB4OPB_GESR0));
Where our mfdcr() macro is stringifying "base + PLB4OPB_GESR0", and passing that to the assembler, which obviously doesn't work.
The mfdcr() macro already checks that the argument is constant using __builtin_constant_p(), and if not calls the out-of-line version of mfdcr(). But in this case GCC is smart enough to notice that "base + PLB4OPB_GESR0" will be constant, even though it's not something we can immediately stringify into a register number.
Segher pointed out that passing the register number to the inline asm as a constant would be better, and in fact it fixes the build error, presumably because it gives GCC a chance to resolve the value.
While we're at it, change mtdcr() similarly.
Reported-by: kernel test robot lkp@intel.com Suggested-by: Segher Boessenkool segher@kernel.crashing.org Signed-off-by: Michael Ellerman mpe@ellerman.id.au Acked-by: Feng Tang feng.tang@intel.com Link: https://lore.kernel.org/r/20210218123058.748882-1-mpe@ellerman.id.au Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/include/asm/dcr-native.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/include/asm/dcr-native.h b/arch/powerpc/include/asm/dcr-native.h index 151dff555f50..9d9e323f5e9b 100644 --- a/arch/powerpc/include/asm/dcr-native.h +++ b/arch/powerpc/include/asm/dcr-native.h @@ -66,8 +66,8 @@ static inline void mtdcrx(unsigned int reg, unsigned int val) #define mfdcr(rn) \ ({unsigned int rval; \ if (__builtin_constant_p(rn) && rn < 1024) \ - asm volatile("mfdcr %0," __stringify(rn) \ - : "=r" (rval)); \ + asm volatile("mfdcr %0, %1" : "=r" (rval) \ + : "n" (rn)); \ else if (likely(cpu_has_feature(CPU_FTR_INDEXED_DCR))) \ rval = mfdcrx(rn); \ else \ @@ -77,8 +77,8 @@ static inline void mtdcrx(unsigned int reg, unsigned int val) #define mtdcr(rn, v) \ do { \ if (__builtin_constant_p(rn) && rn < 1024) \ - asm volatile("mtdcr " __stringify(rn) ",%0" \ - : : "r" (v)); \ + asm volatile("mtdcr %0, %1" \ + : : "n" (rn), "r" (v)); \ else if (likely(cpu_has_feature(CPU_FTR_INDEXED_DCR))) \ mtdcrx(rn, v); \ else \