UPSTREAM: MIPS: smp-cps: Add nothreads kernel parameter

When debugging a new system or core it can be useful to disable the use
of multithreading. Introduce a "nothreads" kernel command line parameter
that can be set in order to do so.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: Matt Redfearn <matt.redfearn@imgtec.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Niklas Cassel <niklas.cassel@axis.com>
Cc: Ezequiel Garcia <ezequiel.garcia@imgtec.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/12340/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
(cherry picked from commit 6422a91385)
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>

arch/mips/kernel/smp-cps.c

@@ -27,14 +27,25 @@
 #include <asm/time.h>
 #include <asm/uasm.h>
 
+static bool threads_disabled;
 static DECLARE_BITMAP(core_power, NR_CPUS);
 
 struct core_boot_config *mips_cps_core_bootcfg;
 
+static int __init setup_nothreads(char *s)
+{
+	threads_disabled = true;
+	return 0;
+}
+early_param("nothreads", setup_nothreads);
+
 static unsigned core_vpe_count(unsigned core)
 {
 	unsigned cfg;
 
+	if (threads_disabled)
+		return 1;
+
 	if ((!config_enabled(CONFIG_MIPS_MT_SMP) || !cpu_has_mipsmt)
 		&& (!config_enabled(CONFIG_CPU_MIPSR6) || !cpu_has_vp))
 		return 1;