Thanks Girish, I have changed a bit your patch but it has been committed in
SVN rev14606.
BIT0 controls the Secure state (transition from Secure to Non-Secure world).
So it can be any of the Non-Secure state: EL2, EL1, EL0.
Replacing 'mov' by 'orr' instructions was the right fix. We start by doing a
load ('ldr') and then we add the EnableGrp0 and EnableGrp1 bits to the
original value.
> -----Original Message-----
> From: Girish K S [mailto:[email protected]]
> Sent: 26 August 2013 05:27
> To: [email protected]
> Cc: Olivier Martin
> Subject: [edk2] AArch64: ArmVExpressPkg: Remove dummy load instr
>
> SCR_EL3 is the control register for setting exception level2
> modified the comment which can mislead.
>
> The "ldr r0, [r1]" is overrided with a immediate "mov ro, #3"
> instruction. This mov instruction will over write the contents
> of the ro register. So remove the ldr instruction if intension
> is to mov #3. Or if previous value has to be retained then ORR
> can be used.
>
> This patch assumes mov is the right instruction to be retained
>
> Contributed-under: TianoCore Contribution Agreement 1.0
> Signed-off-by: Girish K S <[email protected]>
> ---
> .../Scripts/uefi-aarch64-bootstrap/boot.S | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/ArmPlatformPkg/ArmVExpressPkg/Scripts/uefi-aarch64-
> bootstrap/boot.S b/ArmPlatformPkg/ArmVExpressPkg/Scripts/uefi-aarch64-
> bootstrap/boot.S
> index 24d5bb0..031f372 100644
> --- a/ArmPlatformPkg/ArmVExpressPkg/Scripts/uefi-aarch64-
> bootstrap/boot.S
> +++ b/ArmPlatformPkg/ArmVExpressPkg/Scripts/uefi-aarch64-
> bootstrap/boot.S
> @@ -57,7 +57,7 @@ _start:
> b.ne start_ns // skip EL3 initialisation
>
> mov x0, #0x30 // RES1
> - orr x0, x0, #(1 << 0) // Non-secure EL1
> + orr x0, x0, #(1 << 0) // Non-secure EL2
> orr x0, x0, #(1 << 8) // HVC enable
> orr x0, x0, #(1 << 10) // 64-bit EL2
> msr scr_el3, x0
> @@ -87,7 +87,6 @@ _start:
> str w0, [x1], #4
>
> 2: ldr x1, =GIC_CPU_BASE // GICC_CTLR
> - ldr w0, [x1]
> mov w0, #3 // EnableGrp0 | EnableGrp1
> str w0, [x1]
>
> --
> 1.7.9.5
>
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