[PATCH 1/2] MIPS: Use Kconfig to select CPU_NO_EFFICIENT_FFS

[PATCH 1/2] MIPS: Use Kconfig to select CPU_NO_EFFICIENT_FFS

[Paul Burton]

Select CONFIG_CPU_NO_EFFICIENT_FFS via Kconfig when the kernel is
configured for a pre-MIPS32r1 CPU, rather than defining its equivalent
in asm/cpu-features.h based upon overrides of cpu_has_mips* macros.

The latter only works if a platform has an cpu-feature-overrides.h
header which defines cpu_has_mips* macros, which are not generally
needed. There are many cases where we know that the target ISA for a
kernel build is MIPS32r1 or later & thus includes the CLZ instruction,
without requiring any overrides from the platform. Using Kconfig allows
us to take those into account, and more naturally make a decision about
instruction support using information about the target ISA.

Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Zhaoxiu Zeng <zhaoxiu.zeng@gmail.com>
---

 arch/mips/Kconfig                    | 13 ++++++++++++-
 arch/mips/include/asm/cpu-features.h | 10 ----------
 2 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index 71aaa5bcd805..6696eadf7267 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -15,6 +15,7 @@ config MIPS
 	select ARCH_WANT_IPC_PARSE_VERSION
 	select BUILDTIME_EXTABLE_SORT
 	select CLONE_BACKWARDS
+	select CPU_NO_EFFICIENT_FFS if (TARGET_ISA_REV < 1)
 	select CPU_PM if CPU_IDLE
 	select DMA_DIRECT_OPS
 	select GENERIC_ATOMIC64 if !64BIT
@@ -2032,7 +2033,7 @@ config CPU_MIPS64
 	default y if CPU_MIPS64_R1 || CPU_MIPS64_R2 || CPU_MIPS64_R6
 
 #
-# These two indicate the revision of the architecture, either Release 1 or Release 2
+# These indicate the revision of the architecture
 #
 config CPU_MIPSR1
 	bool
@@ -2053,6 +2054,16 @@ config CPU_MIPSR6
 	select MIPS_CRC_SUPPORT
 	select MIPS_SPRAM
 
+config TARGET_ISA_REV
+	int
+	default 1 if CPU_MIPSR1
+	default 2 if CPU_MIPSR2
+	default 6 if CPU_MIPSR6
+	default 0
+	help
+	  Reflects the ISA revision being targeted by the kernel build. This
+	  is effectively the Kconfig equivalent of MIPS_ISA_REV.
+
 config EVA
 	bool
 
diff --git a/arch/mips/include/asm/cpu-features.h b/arch/mips/include/asm/cpu-features.h
index 1f3f7453c1d2..83a27af8ada6 100644
--- a/arch/mips/include/asm/cpu-features.h
+++ b/arch/mips/include/asm/cpu-features.h
@@ -261,16 +261,6 @@
 #endif
 #endif
 
-/* __builtin_constant_p(cpu_has_mips_r) && cpu_has_mips_r */
-#if !((defined(cpu_has_mips32r1) && cpu_has_mips32r1) || \
-	  (defined(cpu_has_mips32r2) && cpu_has_mips32r2) || \
-	  (defined(cpu_has_mips32r6) && cpu_has_mips32r6) || \
-	  (defined(cpu_has_mips64r1) && cpu_has_mips64r1) || \
-	  (defined(cpu_has_mips64r2) && cpu_has_mips64r2) || \
-	  (defined(cpu_has_mips64r6) && cpu_has_mips64r6))
-#define CPU_NO_EFFICIENT_FFS 1
-#endif
-
 #ifndef cpu_has_mips_1
 # define cpu_has_mips_1		(MIPS_ISA_REV < 6)
 #endif
-- 
2.19.1

[PATCH 2/2] lib/gcd: Remove use of CPU_NO_EFFICIENT_FFS macro

[Paul Burton]

The CPU_NO_EFFICIENT_FFS pre-processor macro is no longer used, with all
architectures toggling the equivalent Kconfig symbol
CONFIG_CPU_NO_EFFICIENT_FFS instead. Remove our check for the unused
macro.

Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Zhaoxiu Zeng <zhaoxiu.zeng@gmail.com>

---

 lib/gcd.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/gcd.c b/lib/gcd.c
index 227dea924425..7948ab27f0a4 100644
--- a/lib/gcd.c
+++ b/lib/gcd.c
@@ -10,7 +10,7 @@
  * has decent hardware division.
  */
 
-#if !defined(CONFIG_CPU_NO_EFFICIENT_FFS) && !defined(CPU_NO_EFFICIENT_FFS)
+#if !defined(CONFIG_CPU_NO_EFFICIENT_FFS)
 
 /* If __ffs is available, the even/odd algorithm benchmarks slower. */
 
-- 
2.19.1

Re: [PATCH 1/2] MIPS: Use Kconfig to select CPU_NO_EFFICIENT_FFS

[Paul Burton]

Hello,

Paul Burton wrote:
> Select CONFIG_CPU_NO_EFFICIENT_FFS via Kconfig when the kernel is
> configured for a pre-MIPS32r1 CPU, rather than defining its equivalent
> in asm/cpu-features.h based upon overrides of cpu_has_mips* macros.
> 
> The latter only works if a platform has an cpu-feature-overrides.h
> header which defines cpu_has_mips* macros, which are not generally
> needed. There are many cases where we know that the target ISA for a
> kernel build is MIPS32r1 or later & thus includes the CLZ instruction,
> without requiring any overrides from the platform. Using Kconfig allows
> us to take those into account, and more naturally make a decision about
> instruction support using information about the target ISA.
> 
> Signed-off-by: Paul Burton <paul.burton@mips.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Zhaoxiu Zeng <zhaoxiu.zeng@gmail.com>

Series applied to mips-next.

Thanks,
    Paul

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