ARM: vfp: Add vfp_disable for problematic platforms

Some platforms might not be able to fully utilize VFP when e.g: one CPU
out of two in a SMP complex lacks a VFP unit. Adding code to migrate
task to the CPU which has a VFP unit would be cumbersome and not
performant, instead, just add the ability to disable VFP.
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>

arch/arm/include/asm/vfp.h

@@ -91,4 +91,8 @@
 #define VFPOPDESC_UNUSED_MASK	(0xFF << VFPOPDESC_UNUSED_BIT)
 #define VFPOPDESC_OPDESC_MASK	(~(VFPOPDESC_LENGTH_MASK | VFPOPDESC_UNUSED_MASK))
 
+#ifndef __ASSEMBLY__
+void vfp_disable(void);
+#endif
+
 #endif /* __ASM_VFP_H */

arch/arm/vfp/vfpmodule.c

@@ -445,6 +445,19 @@ static void vfp_enable(void *unused)
 	set_copro_access(access | CPACC_FULL(10) | CPACC_FULL(11));
 }
 
+/* Called by platforms on which we want to disable VFP because it may not be
+ * present on all CPUs within a SMP complex. Needs to be called prior to
+ * vfp_init().
+ */
+void vfp_disable(void)
+{
+	if (VFP_arch) {
+		pr_debug("%s: should be called prior to vfp_init\n", __func__);
+		return;
+	}
+	VFP_arch = 1;
+}
+
 #ifdef CONFIG_CPU_PM
 static int vfp_pm_suspend(void)
 {