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LoongArch: Allow specify SIMD width via kernel parameters

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For power saving or debugging purpose, we usually want to limit the SIMD
(LSX/LASX) usage on a rich feature platform. So allow specify SIMD width
via kernel parameters "simd=".

Allowed values of "simd=" are any integers, and recommended values are:
0:		Disable all SIMD features;
128:		Enable at most 128bit SIMD features;
256:		Enable at most 256bit SIMD features;
-1(default):	Enable as many as possible SIMD features automatically.

Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>
This commit is contained in:
Huacai Chen 2025-10-02 22:39:07 +08:00
parent 98662be7ef
commit 5dcddd268a
1 changed files with 44 additions and 2 deletions
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46
arch/loongarch/kernel/cpu-probe.c
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@ -52,6 +52,48 @@ static inline void cpu_set_fpu_fcsr_mask(struct cpuinfo_loongarch *c)
c->fpu_mask = ~(fcsr0 ^ fcsr1) & ~mask;
}
/* simd = -1/0/128/256 */
static unsigned int simd = -1U;
static int __init cpu_setup_simd(char *str)
{
get_option(&str, &simd);
pr_info("Set SIMD width = %u\n", simd);
return 0;
}
early_param("simd", cpu_setup_simd);
static int __init cpu_final_simd(void)
{
struct cpuinfo_loongarch *c = &cpu_data[0];
if (simd < 128) {
c->options &= ~LOONGARCH_CPU_LSX;
elf_hwcap &= ~HWCAP_LOONGARCH_LSX;
}
if (simd < 256) {
c->options &= ~LOONGARCH_CPU_LASX;
elf_hwcap &= ~HWCAP_LOONGARCH_LASX;
}
simd = 0;
if (c->options & LOONGARCH_CPU_LSX)
simd = 128;
if (c->options & LOONGARCH_CPU_LASX)
simd = 256;
pr_info("Final SIMD width = %u\n", simd);
return 0;
}
arch_initcall(cpu_final_simd);
static inline void set_elf_platform(int cpu, const char *plat)
{
if (cpu == 0)
@ -134,13 +176,13 @@ static void cpu_probe_common(struct cpuinfo_loongarch *c)
elf_hwcap |= HWCAP_LOONGARCH_FPU;
}
#ifdef CONFIG_CPU_HAS_LSX
if (config & CPUCFG2_LSX) {
if ((config & CPUCFG2_LSX) && (simd >= 128)) {
c->options |= LOONGARCH_CPU_LSX;
elf_hwcap |= HWCAP_LOONGARCH_LSX;
}
#endif
#ifdef CONFIG_CPU_HAS_LASX
if (config & CPUCFG2_LASX) {
if ((config & CPUCFG2_LASX) && (simd >= 256)) {
c->options |= LOONGARCH_CPU_LASX;
elf_hwcap |= HWCAP_LOONGARCH_LASX;
}