[PATCH 2/3] ARC: ARCv2: support loop buffer (LPB) disabling

[Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>]

On HS cores, loop buffer (LPB) is programmable in runtime and can
be optionally disabled.

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@synopsys.com>
---
 arch/arc/Kconfig       | 6 ++++++
 arch/arc/kernel/head.S | 8 ++++++++
 2 files changed, 14 insertions(+)

diff --git a/arch/arc/Kconfig b/arch/arc/Kconfig
index 2d4f85dc914e..270504d4fdf5 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -471,6 +471,12 @@ config ARC_IRQ_NO_AUTOSAVE
 	  This is programmable and can be optionally disabled in which case
 	  software INTERRUPT_PROLOGUE/EPILGUE do the needed work
 
+config ARC_LPB_DISABLE
+	bool "Disable loop buffer (LPB)"
+	help
+	  On HS cores, loop buffer (LPB) is programmable in runtime and can
+	  be optionally disabled.
+
 endif # ISA_ARCV2
 
 endmenu   # "ARC CPU Configuration"
diff --git a/arch/arc/kernel/head.S b/arch/arc/kernel/head.S
index 6eb23f1545ee..17fd1ed700cc 100644
--- a/arch/arc/kernel/head.S
+++ b/arch/arc/kernel/head.S
@@ -59,6 +59,14 @@
 	bclr	r5, r5, STATUS_AD_BIT
 #endif
 	kflag	r5
+
+#ifdef CONFIG_ARC_LPB_DISABLE
+	lr	r5, [ARC_REG_LPB_BUILD]
+	breq    r5, 0, 1f		; LPB doesn't exist
+	mov	r5, 1
+	sr	r5, [ARC_REG_LPB_CTRL]
+1:
+#endif /* CONFIG_ARC_LPB_DISABLE */
 #endif
 	; Config DSP_CTRL properly, so kernel may use integer multiply,
 	; multiply-accumulate, and divide operations
-- 
2.21.3