ARM: Introduce function to switch to hypervisor mode

On some of the SoCs one cannot enable hypervisor mode directly from the
u-boot because the ROM code puts the chip to supervisor mode after it
jumps to boot loader. Hence introduce a weak function which can be
overridden based on the SoC type and switch to hypervisor mode in a
custom way.

Cc: beagleboard-x15@googlegroups.com
Signed-off-by: Keerthy <j-keerthy@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>

arch/arm/cpu/armv7/start.S

@@ -17,6 +17,7 @@
 #include <config.h>
 #include <asm/system.h>
 #include <linux/linkage.h>
+#include <asm/armv7.h>
 
 /*************************************************************************
  *
@@ -30,11 +31,24 @@
 
 	.globl	reset
 	.globl	save_boot_params_ret
+#ifdef CONFIG_ARMV7_LPAE
+	.global	switch_to_hypervisor_ret
+#endif
 
 reset:
 	/* Allow the board to save important registers */
 	b	save_boot_params
 save_boot_params_ret:
+#ifdef CONFIG_ARMV7_LPAE
+/*
+ * check for Hypervisor support
+ */
+	mrc	p15, 0, r0, c0, c1, 1		@ read ID_PFR1
+	and	r0, r0, #CPUID_ARM_VIRT_MASK	@ mask virtualization bits
+	cmp	r0, #(1 << CPUID_ARM_VIRT_SHIFT)
+	beq	switch_to_hypervisor
+switch_to_hypervisor_ret:
+#endif
 	/*
 	 * disable interrupts (FIQ and IRQ), also set the cpu to SVC32 mode,
 	 * except if in HYP mode already
@@ -103,6 +117,13 @@ ENTRY(save_boot_params)
 ENDPROC(save_boot_params)
 	.weak	save_boot_params
 
+#ifdef CONFIG_ARMV7_LPAE
+ENTRY(switch_to_hypervisor)
+	b	switch_to_hypervisor_ret
+ENDPROC(switch_to_hypervisor)
+	.weak	switch_to_hypervisor
+#endif
+
 /*************************************************************************
  *
  * cpu_init_cp15

arch/arm/include/asm/system.h

@@ -223,6 +223,10 @@ void __noreturn psci_system_reset(bool smc);
  */
 void save_boot_params_ret(void);
 
+#ifdef CONFIG_ARMV7_LPAE
+void switch_to_hypervisor_ret(void);
+#endif
+
 #define nop() __asm__ __volatile__("mov\tr0,r0\t@ nop\n\t");
 
 #ifdef __ARM_ARCH_7A__