linux-kernel - Re: [PATCH v2 2/4] ARC: ARCv2: support loop buffer (LPB) disabling

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Message-ID: <CY4PR1201MB0136B3C5A25EA943379FFCD0DE9B0@CY4PR1201MB0136.namprd12.prod.outlook.com>
Date:   Thu, 18 Jun 2020 19:50:56 +0000
From:   Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
To:     Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>,
        Vineet Gupta <Vineet.Gupta1@...opsys.com>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Alexey Brodkin <Alexey.Brodkin@...opsys.com>
Subject: Re: [PATCH v2 2/4] ARC: ARCv2: support loop buffer (LPB) disabling

Hi Vineet,

could you also peek this patch to for-curr as we don't have any disagreement about it?

I'll respin the rest of the patches later. Thanks.
---
 Eugeniy Paltsev


________________________________________
From: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
Sent: Thursday, June 4, 2020 20:39
To: linux-snps-arc@...ts.infradead.org; Vineet Gupta
Cc: linux-kernel@...r.kernel.org; Alexey Brodkin; Eugeniy Paltsev
Subject: [PATCH v2 2/4] ARC: ARCv2: support loop buffer (LPB) disabling

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

Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.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 7034c217708f..2dc142c8e1f5 100644
--- a/arch/arc/Kconfig
+++ b/arch/arc/Kconfig
@@ -473,6 +473,12 @@ 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