Re: [PATCH] LoongArch: detect and disable sc.q if erratic

[kernel test robot <lkp@intel.com>]

Hi Xi,

kernel test robot noticed the following build errors:

[auto build test ERROR on soc/for-next]
[also build test ERROR on linus/master v7.0-rc7 next-20260406]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Xi-Ruoyao/LoongArch-detect-and-disable-sc-q-if-erratic/20260407-193425
base:   https://git.kernel.org/pub/scm/linux/kernel/git/soc/soc.git for-next
patch link:    https://lore.kernel.org/r/20260402044732.164294-2-xry111%40xry111.site
patch subject: [PATCH] LoongArch: detect and disable sc.q if erratic
config: loongarch-allnoconfig (https://download.01.org/0day-ci/archive/20260407/202604072314.9J2SQEFo-lkp@intel.com/config)
compiler: clang version 23.0.0git (https://github.com/llvm/llvm-project c80443cd37b2e2788cba67ffa180a6331e5f0791)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260407/202604072314.9J2SQEFo-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202604072314.9J2SQEFo-lkp@intel.com/

All errors (new ones prefixed by >>):

>> arch/loongarch/kernel/cpu-probe.c:151:23: error: invalid operand for instruction
     151 |                 "move\t%[tmp], $r0\n\t"
         |                                     ^
   <inline asm>:3:22: note: instantiated into assembly here
       3 |         sc.q    $a2, $a0, $a1, 0
         |                                ^
   1 error generated.


vim +151 arch/loongarch/kernel/cpu-probe.c

   134	
   135	/*
   136	 * Some LoongArch has broken sc.q which incorrectly handles the upper word
   137	 * when the lower word is zero. Newer firmware versions (such as the 202602
   138	 * release from Loongson) seem to contain a workaround for this issue.
   139	 *
   140	 * Disable sc.q if erratic to ensure reliability and compatibility.
   141	 */
   142	static bool sc_q_is_sane(void)
   143	{
   144		struct {
   145			long word[2];
   146		} __aligned(16) mem;
   147		register long tmp;
   148	
   149		asm (
   150			"1:ll.d\t$r0, %[mem]\n\t"
 > 151			"move\t%[tmp], $r0\n\t"
   152			"sc.q\t%[tmp], %[one], %[mem]\n\t"
   153			"beqz\t%[tmp], 1b"
   154			: [mem] "=ZB" (mem), [tmp] "=&r" (tmp)
   155			: [one] "r" (1));
   156	
   157		if (mem.word[1] != 1) {
   158			pr_warn_once("Warning: sc.q is erratic on this platform, disabling for both kernel and HWCAP. Please try a firmware update.");
   159			return false;
   160		}
   161	
   162		return true;
   163	}
   164	

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