[PATCH 01/14] ARC: ARCv2: handle DSP presence in HW

[Eugeniy Paltsev]

In case of DSP extension presence in HW some instructions
(related to integer multiply, multiply-accumulate, and divide
operation) executes on this DSP execution unit. So their
execution will depend on dsp configuration register (DSP_CTRL)
As we want these instructions to execute the same way regardless
of DSP presence we need to set DSP_CTRL properly.

NOTE:
we do the same adjustments in Linux kernel, see in kernel tree:
commit 4827d0cf744e ("ARC: handle DSP presence in HW")

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev at synopsys.com>
---
 arch/arc/include/asm/arcregs.h |  1 +
 arch/arc/lib/start.S           | 15 +++++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/arch/arc/include/asm/arcregs.h b/arch/arc/include/asm/arcregs.h
index fff6591c681..f3cd4a889ac 100644
--- a/arch/arc/include/asm/arcregs.h
+++ b/arch/arc/include/asm/arcregs.h
@@ -100,6 +100,7 @@
 
 /* DSP-extensions related auxiliary registers */
 #define ARC_AUX_DSP_BUILD	0x7A
+#define ARC_AUX_DSP_CTRL	0x59F
 
 /* ARC Subsystems related auxiliary registers */
 #define ARC_AUX_SUBSYS_BUILD	0xF0
diff --git a/arch/arc/lib/start.S b/arch/arc/lib/start.S
index 8c744f5be7f..016ae85be23 100644
--- a/arch/arc/lib/start.S
+++ b/arch/arc/lib/start.S
@@ -61,6 +61,21 @@ ENTRY(_start)
 1:
 #endif
 
+#ifdef CONFIG_ISA_ARCV2
+	; In case of DSP extension presence in HW some instructions
+	; (related to integer multiply, multiply-accumulate, and divide
+	; operation) executes on this DSP execution unit. So their
+	; execution will depend on dsp configuration register (DSP_CTRL)
+	; As we want these instructions to execute the same way regardless
+	; of DSP presence we need to set DSP_CTRL properly.
+	lr	r5, [ARC_AUX_DSP_BUILD]
+	bmsk	r5, r5, 7
+	breq    r5, 0, 1f
+	mov	r5, 0
+	sr	r5, [ARC_AUX_DSP_CTRL]
+1:
+#endif
+
 #ifdef __ARC_UNALIGNED__
 	/*
 	 * Enable handling of unaligned access in the CPU as by default
-- 
2.21.1