arm64: head: create a new function for setting the boot_cpu_mode flag

Currently, the code for setting the __cpu_boot_mode flag is munged in
with el2_setup. This makes things difficult on a BE bringup as a
memory access has to have occurred before el2_setup which is the place
that we'd like to set the endianess on the current EL.

Create a new function for setting __cpu_boot_mode and have el2_setup
return the mode the CPU. Also define a new constant in virt.h,
BOOT_CPU_MODE_EL1, for readability.

Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Matthew Leach <matthew.leach@arm.com>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

1 files changed, 25 insertions, 9 deletions

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index bf7efdf2d7e7..775ecb313ee7 100644
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -123,8 +123,9 @@
 
 ENTRY(stext)
         mov     x21, x0                         // x21=FDT
+        bl      el2_setup                       // Drop to EL1, w20=cpu_boot_mode
         bl      __calc_phys_offset              // x24=PHYS_OFFSET, x28=PHYS_OFFSET-PAGE_OFFSET
-        bl      el2_setup                       // Drop to EL1
+        bl      set_cpu_boot_mode_flag
         mrs     x22, midr_el1                   // x22=cpuid
         mov     x0, x22
         bl      lookup_processor_type
@@ -150,21 +151,20 @@ ENDPROC(stext)
 /*
  * If we're fortunate enough to boot at EL2, ensure that the world is
  * sane before dropping to EL1.
+ *
+ * Returns either BOOT_CPU_MODE_EL1 or BOOT_CPU_MODE_EL2 in x20 if
+ * booted in EL1 or EL2 respectively.
  */
 ENTRY(el2_setup)
         mrs     x0, CurrentEL
         cmp     x0, #PSR_MODE_EL2t
         ccmp    x0, #PSR_MODE_EL2h, #0x4, ne
-        ldr     x0, =__boot_cpu_mode            // Compute __boot_cpu_mode
-        add     x0, x0, x28
         b.eq    1f
-        str     wzr, [x0]                       // Remember we don't have EL2...
+        mov     w20, #BOOT_CPU_MODE_EL1         // This cpu booted in EL1
         ret
 
         /* Hyp configuration. */
-1:      ldr     w1, =BOOT_CPU_MODE_EL2
-        str     w1, [x0, #4]                    // This CPU has EL2
-        mov     x0, #(1 << 31)                  // 64-bit EL1
+1:      mov     x0, #(1 << 31)                  // 64-bit EL1
         msr     hcr_el2, x0
 
         /* Generic timers. */
@@ -204,10 +204,25 @@ ENTRY(el2_setup)
                       PSR_MODE_EL1h)
         msr     spsr_el2, x0
         msr     elr_el2, lr
+        mov     w20, #BOOT_CPU_MODE_EL2         // This CPU booted in EL2
         eret
 ENDPROC(el2_setup)
 
 /*
+ * Sets the __boot_cpu_mode flag depending on the CPU boot mode passed
+ * in x20. See arch/arm64/include/asm/virt.h for more info.
+ */
+ENTRY(set_cpu_boot_mode_flag)
+        ldr     x1, =__boot_cpu_mode            // Compute __boot_cpu_mode
+        add     x1, x1, x28
+        cmp     w20, #BOOT_CPU_MODE_EL2
+        b.ne    1f
+        add     x1, x1, #4
+1:      str     w20, [x1]                       // This CPU has booted in EL1
+        ret
+ENDPROC(set_cpu_boot_mode_flag)
+
+/*
  * We need to find out the CPU boot mode long after boot, so we need to
  * store it in a writable variable.
  *
@@ -234,8 +249,9 @@ ENTRY(__boot_cpu_mode)
          * cores are held until we're ready for them to initialise.
          */
 ENTRY(secondary_holding_pen)
-        bl      __calc_phys_offset              // x24=phys offset
-        bl      el2_setup                       // Drop to EL1
+        bl      el2_setup                       // Drop to EL1, w20=cpu_boot_mode
+        bl      __calc_phys_offset              // x24=PHYS_OFFSET, x28=PHYS_OFFSET-PAGE_OFFSET
+        bl      set_cpu_boot_mode_flag
         mrs     x0, mpidr_el1
         ldr     x1, =MPIDR_HWID_BITMASK
         and     x0, x0, x1