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.palt...@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
