[U-Boot] [PATCH 1/2] ARM: Introduce function to switch to hypervisor mode

[Keerthy]

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 at googlegroups.com
Signed-off-by: Keerthy <j-keerthy at ti.com>
---
 arch/arm/cpu/armv7/start.S    | 15 +++++++++++++++
 arch/arm/include/asm/system.h |  1 +
 2 files changed, 16 insertions(+)

diff --git a/arch/arm/cpu/armv7/start.S b/arch/arm/cpu/armv7/start.S
index 691e5d3..4fb3d58 100644
--- a/arch/arm/cpu/armv7/start.S
+++ b/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 +31,20 @@
 
 	.globl	reset
 	.globl	save_boot_params_ret
+	.global	switch_to_hypervisor_ret
 
 reset:
 	/* Allow the board to save important registers */
 	b	save_boot_params
 save_boot_params_ret:
+/*
+ * 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:
 	/*
 	 * disable interrupts (FIQ and IRQ), also set the cpu to SVC32 mode,
 	 * except if in HYP mode already
@@ -103,6 +113,11 @@ ENTRY(save_boot_params)
 ENDPROC(save_boot_params)
 	.weak	save_boot_params
 
+ENTRY(switch_to_hypervisor)
+	b	switch_to_hypervisor_ret
+ENDPROC(switch_to_hypervisor)
+	.weak	switch_to_hypervisor
+
 /*************************************************************************
  *
  * cpu_init_cp15
diff --git a/arch/arm/include/asm/system.h b/arch/arm/include/asm/system.h
index 2bdc0be..d1a95b0 100644
--- a/arch/arm/include/asm/system.h
+++ b/arch/arm/include/asm/system.h
@@ -226,6 +226,7 @@ void __noreturn psci_system_reset(bool smc);
  * should use 'b' or 'bx' to return to save_boot_params_ret.
  */
 void save_boot_params_ret(void);
+void switch_to_hypervisor_ret(void);
 
 #define isb() __asm__ __volatile__ ("" : : : "memory")
 
-- 
1.9.1