[PATCH v2] bootwrapper: SVE: Enable SVE for EL2 and below

[Dave Martin]

By default, SVE will trap to EL3.  We also want to make sure that
lower ELs have access to the full SVE vector length before dropping
down.

This patch programs CPTR_EL3 and ZCR_EL3 appropriately to enable
SVE for lower exception levels and make sure that they can use the
full vector length provided by the hardware.

Signed-off-by: Dave Martin <Dave.Martin at arm.com>
Cc: Mark Rutland <mark.rutland at arm.com>
Cc: Alex Bennée <alex.bennee at linaro.org>
---

This is basically the same as v1 [1], but rebased to an up-to-date
bootwrapper tree.  (I was previously tracking Catalin's tree, which no
longer exists...)

[1] [PATCH] bootwrapper: SVE: Enable SVE for EL2 and below
http://lists.infradead.org/pipermail/linux-arm-kernel/2017-August/527000.html


 arch/aarch64/boot.S            | 13 +++++++++++++
 arch/aarch64/include/asm/cpu.h |  5 +++++
 2 files changed, 18 insertions(+)

diff --git a/arch/aarch64/boot.S b/arch/aarch64/boot.S
index ceeee76..f7d795a 100644
--- a/arch/aarch64/boot.S
+++ b/arch/aarch64/boot.S
@@ -45,6 +45,19 @@ _start:
 
 	msr	cptr_el3, xzr			// Disable copro. traps to EL3
 
+	mrs	x0, id_aa64pfr0_el1
+	ubfx	x0, x0, #32, #4			// SVE present?
+	cbz	x0, 1f				// Skip SVE init if not
+
+	mrs	x0, cptr_el3
+	orr	x0, x0, #CPTR_EL3_EZ		// enable SVE
+	msr	cptr_el3, x0
+	isb
+
+	mov	x0, #ZCR_EL3_LEN_MASK		// SVE: Enable full vector len
+	msr	ZCR_EL3, x0			// for EL2.
+
+1:
 	ldr	x0, =CNTFRQ
 	msr	cntfrq_el0, x0
 
diff --git a/arch/aarch64/include/asm/cpu.h b/arch/aarch64/include/asm/cpu.h
index 66726ef..ccb5397 100644
--- a/arch/aarch64/include/asm/cpu.h
+++ b/arch/aarch64/include/asm/cpu.h
@@ -27,6 +27,11 @@
 #define SPSR_EL2H		(9 << 0)	/* EL2 Handler mode */
 #define SPSR_HYP		(0x1a << 0)	/* M[3:0] = hyp, M[4] = AArch32 */
 
+#define CPTR_EL3_EZ		(1 << 8)
+
+#define ZCR_EL3			s3_6_c1_c2_0
+#define ZCR_EL3_LEN_MASK	0x1ff
+
 #define SCTLR_EL1_CP15BEN	(1 << 5)
 #define SCTLR_EL1_RES1		(3 << 28 | 3 << 22 | 1 << 11)
 
-- 
2.1.4