linux-kernel - [PATCH v2] MIPS: Provide Kconfig option for default IEEE 754 conformance mode

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Date:   Sat,  1 Aug 2020 14:11:46 +0800
From:   Jiaxun Yang <jiaxun.yang@...goat.com>
To:     linux-mips@...r.kernel.org
Cc:     Jiaxun Yang <jiaxun.yang@...goat.com>,
        WANG Xuerui <git@...0n.name>,
        Serge Semin <fancer.lancer@...il.com>,
        Huacai Chen <chenhc@...ote.com>,
        Thomas Bogendoerfer <tsbogend@...ha.franken.de>,
        Paul Burton <paulburton@...nel.org>,
        Serge Semin <Sergey.Semin@...kalelectronics.ru>,
        Zhou Yanjie <zhouyanjie@...o.com>,
        周琰杰 (Zhou Yanjie) 
        <zhouyanjie@...yeetech.com>,
        Liangliang Huang <huanglllzu@...il.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2] MIPS: Provide Kconfig option for default IEEE 754 conformance mode

Requested by downstream distros, a Kconfig option for default
IEEE 754 conformance mode allows them to set their mode to
relaxed by default.

Signed-off-by: Jiaxun Yang <jiaxun.yang@...goat.com>
Reviewed-by: WANG Xuerui <git@...0n.name>
Reviewed-by: Serge Semin <fancer.lancer@...il.com>
Reviewed-by: Huacai Chen <chenhc@...ote.com>

--
v2: Reword according to Xuerui's suggestion.
---
 arch/mips/Kconfig            | 22 ++++++++++++++++++++++
 arch/mips/kernel/cpu-probe.c | 12 +++++++++++-
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index eaf7519e3033..ac35df2b9133 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -2899,6 +2899,28 @@ config MIPS_NR_CPU_NR_MAP
 	default 1024 if MIPS_NR_CPU_NR_MAP_1024
 	default NR_CPUS if !MIPS_NR_CPU_NR_MAP_1024
 
+choice
+	prompt "Default IEEE 754 conformance mode"
+	default IEEE754_DEFAULT_STRICT
+	help
+	  Sets the default IEEE 754 conformance mode, same as overriding the
+	  default value for the ieee754= kernel parameter. See the kernel
+	  parameter for details.
+
+	config IEEE754_DEFAULT_STRICT
+		bool "Strict"
+
+	config IEEE754_DEFAULT_LEGACY
+		bool "Legacy"
+
+	config IEEE754_DEFAULT_STD2008
+		bool "2008"
+
+	config IEEE754_DEFAULT_RELAXED
+		bool "Relaxed"
+
+endchoice
+
 #
 # Timer Interrupt Frequency Configuration
 #
diff --git a/arch/mips/kernel/cpu-probe.c b/arch/mips/kernel/cpu-probe.c
index c231c1b67889..a5b8fe019afc 100644
--- a/arch/mips/kernel/cpu-probe.c
+++ b/arch/mips/kernel/cpu-probe.c
@@ -157,7 +157,17 @@ static void cpu_set_fpu_2008(struct cpuinfo_mips *c)
  * IEEE 754 conformance mode to use.  Affects the NaN encoding and the
  * ABS.fmt/NEG.fmt execution mode.
  */
-static enum { STRICT, LEGACY, STD2008, RELAXED } ieee754 = STRICT;
+enum ieee754_mode { STRICT, LEGACY, STD2008, RELAXED };
+
+#if defined(CONFIG_IEEE754_DEFAULT_STRICT)
+static enum ieee754_mode ieee754 = STRICT;
+#elif defined(CONFIG_IEEE754_DEFAULT_LEGACY)
+static enum ieee754_mode ieee754 = LEGACY;
+#elif defined(CONFIG_IEEE754_DEFAULT_STD2008)
+static enum ieee754_mode ieee754 = STD2008;
+#elif defined(CONFIG_IEEE754_DEFAULT_RELAXED)
+static enum ieee754_mode ieee754 = RELAXED;
+#endif
 
 /*
  * Set the IEEE 754 NaN encodings and the ABS.fmt/NEG.fmt execution modes
-- 
2.28.0.rc1