ARC: ARCv2: handle DSP presence in HW

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@synopsys.com>
Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>

diff --git a/arch/arc/include/asm/arcregs.h b/arch/arc/include/asm/arcregs.h
index fff6591..f3cd4a8 100644 (file)
--- 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 8c744f5..016ae85 100644 (file)
--- 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