MIPS: Probe for presence of KScratch registers.

Probe c0_config4 for KScratch registers and report them in /proc/cpuinfo.

Signed-off-by: David Daney <[e-mail]>
To: [e-mail]
Patchwork: https://patchwork.linux-mips.org/patch/1877/
Signed-off-by: Ralf Baechle <[e-mail]>

arch/mips/include/asm/cpu-info.h

···
 	unsigned int		watch_reg_use_cnt; /* Usable by ptrace */
 #define NUM_WATCH_REGS 4
 	u16			watch_reg_masks[NUM_WATCH_REGS];
+	unsigned int		kscratch_mask; /* Usable KScratch mask. */
 } __attribute__((aligned(SMP_CACHE_BYTES)));
 
 extern struct cpuinfo_mips cpu_data[];

arch/mips/kernel/cpu-probe.c

···
 	    && cpu_has_tlb)
 		c->tlbsize += (config4 & MIPS_CONF4_MMUSIZEEXT) * 0x40;
 
+	c->kscratch_mask = (config4 >> 16) & 0xff;
+
 	return config4 & MIPS_CONF_M;
 }
 

arch/mips/kernel/proc.c

···
 		);
 	seq_printf(m, "shadow register sets\t: %d\n",
 		       cpu_data[n].srsets);
+	seq_printf(m, "kscratch registers\t: %d\n",
+		   hweight8(cpu_data[n].kscratch_mask));
 	seq_printf(m, "core\t\t\t: %d\n", cpu_data[n].core);
 
 	sprintf(fmt, "VCE%%c exceptions\t\t: %s\n",