From: Vineet Gupta <vgupta@synopsys.com>
Date: Tue, 21 Jun 2016 08:54:33 +0000 (+0530)
Subject: ARCv2: smp-boot: wake_flag polling by non-Masters needs to be uncached
X-Git-Tag: v4.10-rc6~7^2~1
X-Git-Url: https://git.kernel.dk/?p=linux-2.6-block.git;a=commitdiff_plain;h=78f824d4312a8944f5340c6b161bba3bf2c81096

ARCv2: smp-boot: wake_flag polling by non-Masters needs to be uncached

This is needed on HS38 cores, for setting up IO-Coherency aperture properly

The polling could perturb the caches and coherecy fabric which could be
wrong in the small window when Master is setting up IOC aperture etc
in arc_cache_init()

We do it only for ARCv2 based builds to not affect EZChip ARCompact
based platform.

Signed-off-by: Vineet Gupta <vgupta@synopsys.com>
---

diff --git a/arch/arc/kernel/smp.c b/arch/arc/kernel/smp.c
index 44a0d21ed342..2afbafadb6ab 100644
--- a/arch/arc/kernel/smp.c
+++ b/arch/arc/kernel/smp.c
@@ -90,10 +90,23 @@ void __init smp_cpus_done(unsigned int max_cpus)
  */
 static volatile int wake_flag;
 
+#ifdef CONFIG_ISA_ARCOMPACT
+
+#define __boot_read(f)		f
+#define __boot_write(f, v)	f = v
+
+#else
+
+#define __boot_read(f)		arc_read_uncached_32(&f)
+#define __boot_write(f, v)	arc_write_uncached_32(&f, v)
+
+#endif
+
 static void arc_default_smp_cpu_kick(int cpu, unsigned long pc)
 {
 	BUG_ON(cpu == 0);
-	wake_flag = cpu;
+
+	__boot_write(wake_flag, cpu);
 }
 
 void arc_platform_smp_wait_to_boot(int cpu)
@@ -102,10 +115,10 @@ void arc_platform_smp_wait_to_boot(int cpu)
 	if (IS_ENABLED(CONFIG_ARC_SMP_HALT_ON_RESET))
 		return;
 
-	while (wake_flag != cpu)
+	while (__boot_read(wake_flag) != cpu)
 		;
 
-	wake_flag = 0;
+	__boot_write(wake_flag, 0);
 }
 
 const char *arc_platform_smp_cpuinfo(void)