Commit 5dcddd26 authored by Huacai Chen's avatar Huacai Chen
Browse files

LoongArch: Allow specify SIMD width via kernel parameters 



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: default avatarHuacai Chen <chenhuacai@loongson.cn>
parent 98662be7

arch/loongarch/kernel/cpu-probe.c

+44 −2
Original line number Diff line number Diff line
@@ -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;

	}