[ARM] Provide a method to alter the control register

i.MX needs to tweak the control register to support CPU frequency
scaling. Rather than have folk blindly try and change the control
register by writing to it and then wondering why it doesn't work,
provide a method (which is safe for UP only, and therefore only
available for UP) to achieve this.

Signed-off-by: Russell King <[e-mail]>

include/asm-arm/system.h

···
 extern unsigned long cr_no_alignment;	/* defined in entry-armv.S */
 extern unsigned long cr_alignment;	/* defined in entry-armv.S */
 
+#ifndef CONFIG_SMP
+static inline void adjust_cr(unsigned long mask, unsigned long set)
+{
+	unsigned long flags, cr;
+
+	mask &= ~CR_A;
+
+	set &= mask;
+
+	local_irq_save(flags);
+
+	cr_no_alignment = (cr_no_alignment & ~mask) | set;
+	cr_alignment = (cr_alignment & ~mask) | set;
+
+	set_cr((get_cr() & ~mask) | set);
+
+	local_irq_restore(flags);
+}
+#endif
+
 #define UDBG_UNDEFINED	(1 << 0)
 #define UDBG_SYSCALL	(1 << 1)
 #define UDBG_BADABORT	(1 << 2)