summaryrefslogtreecommitdiffstats
path: root/arch/mips/Kconfig
diff options
context:
space:
mode:
authorWANG Xuerui <git@xen0n.name>2020-05-23 21:37:01 +0800
committerThomas Bogendoerfer <tsbogend@alpha.franken.de>2020-05-24 09:26:55 +0200
commitec7a93188a75b57b9f704db6862e7137f01aa80b (patch)
tree84907800878283ad5358796589613757ed9783f2 /arch/mips/Kconfig
parent8267e78f020a8de2752754c42ec1d56e92431477 (diff)
downloadlinux-ec7a93188a75b57b9f704db6862e7137f01aa80b.tar.bz2
MIPS: emulate CPUCFG instruction on older Loongson64 cores
CPUCFG is the instruction for querying processor characteristics on newer Loongson processors, much like CPUID of x86. Since the instruction is supposedly designed to provide a unified way to do feature detection (without having to, for example, parse /proc/cpuinfo which is too heavyweight), it is important to provide compatibility for older cores without native support. Fortunately, most of the fields can be synthesized without changes to semantics. Performance is not really big a concern, because feature detection logic is not expected to be invoked very often in typical userland applications. The instruction can't be emulated on LOONGSON_2EF cores, according to FlyGoat's experiments. Because the LWC2 opcode is assigned to other valid instructions on 2E and 2F, no RI exception is raised for us to intercept. So compatibility is only extended back furthest to Loongson-3A1000. Loongson-2K is covered too, as it is basically a remix of various blocks from the 3A/3B models from a kernel perspective. This is lightly based on Loongson's work on their Linux 3.10 fork, for being the authority on the right feature flags to fill in, where things aren't otherwise discoverable. Signed-off-by: WANG Xuerui <git@xen0n.name> Reviewed-by: Jiaxun Yang <jiaxun.yang@flygoat.com> Cc: Huacai Chen <chenhc@lemote.com> Cc: Jiaxun Yang <jiaxun.yang@flygoat.com> Cc: Tiezhu Yang <yangtiezhu@loongson.cn> Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Diffstat (limited to 'arch/mips/Kconfig')
-rw-r--r--arch/mips/Kconfig12
1 files changed, 12 insertions, 0 deletions
diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index f347312ecd74..c5fe30c78402 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig
@@ -1441,6 +1441,18 @@ config CPU_LOONGSON3_WORKAROUNDS
If unsure, please say Y.
+config CPU_LOONGSON3_CPUCFG_EMULATION
+ bool "Emulate the CPUCFG instruction on older Loongson cores"
+ default y
+ depends on CPU_LOONGSON64
+ help
+ Loongson-3A R4 and newer have the CPUCFG instruction available for
+ userland to query CPU capabilities, much like CPUID on x86. This
+ option provides emulation of the instruction on older Loongson
+ cores, back to Loongson-3A1000.
+
+ If unsure, please say Y.
+
config CPU_LOONGSON2E
bool "Loongson 2E"
depends on SYS_HAS_CPU_LOONGSON2E