powerpc: Expose TSCR via sysfs

The thread switch control register (TSCR) is a per core register
that configures how the CPU shares resources between SMT threads.

Exposing it via sysfs allows us to tune it at run time.
Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/sysfs.c

@@ -485,6 +485,7 @@ SYSFS_PMCSETUP(mmcra, SPRN_MMCRA);
 SYSFS_SPRSETUP(purr, SPRN_PURR);
 SYSFS_SPRSETUP(spurr, SPRN_SPURR);
 SYSFS_SPRSETUP(pir, SPRN_PIR);
+SYSFS_SPRSETUP(tscr, SPRN_TSCR);
 
 /*
   Lets only enable read for phyp resources and
@@ -495,6 +496,7 @@ static DEVICE_ATTR(mmcra, 0600, show_mmcra, store_mmcra);
 static DEVICE_ATTR(spurr, 0400, show_spurr, NULL);
 static DEVICE_ATTR(purr, 0400, show_purr, store_purr);
 static DEVICE_ATTR(pir, 0400, show_pir, NULL);
+static DEVICE_ATTR(tscr, 0600, show_tscr, store_tscr);
 
 /*
  * This is the system wide DSCR register default value. Any
@@ -785,6 +787,9 @@ static int register_cpu_online(unsigned int cpu)
 
 	if (cpu_has_feature(CPU_FTR_PPCAS_ARCH_V2))
 		device_create_file(s, &dev_attr_pir);
+
+	if (cpu_has_feature(CPU_FTR_ARCH_206))
+		device_create_file(s, &dev_attr_tscr);
 #endif /* CONFIG_PPC64 */
 
 #ifdef CONFIG_PPC_FSL_BOOK3E
@@ -867,6 +872,9 @@ static int unregister_cpu_online(unsigned int cpu)
 
 	if (cpu_has_feature(CPU_FTR_PPCAS_ARCH_V2))
 		device_remove_file(s, &dev_attr_pir);
+
+	if (cpu_has_feature(CPU_FTR_ARCH_206))
+		device_remove_file(s, &dev_attr_tscr);
 #endif /* CONFIG_PPC64 */
 
 #ifdef CONFIG_PPC_FSL_BOOK3E