diff options
Diffstat (limited to 'arch/mips/include/asm/timex.h')
| -rw-r--r-- | arch/mips/include/asm/timex.h | 65 |
1 files changed, 47 insertions, 18 deletions
diff --git a/arch/mips/include/asm/timex.h b/arch/mips/include/asm/timex.h index c5424757da65..b05bb70a2e46 100644 --- a/arch/mips/include/asm/timex.h +++ b/arch/mips/include/asm/timex.h @@ -4,12 +4,16 @@ * for more details. * * Copyright (C) 1998, 1999, 2003 by Ralf Baechle + * Copyright (C) 2014 by Maciej W. Rozycki */ #ifndef _ASM_TIMEX_H #define _ASM_TIMEX_H #ifdef __KERNEL__ +#include <linux/compiler.h> + +#include <asm/cpu.h> #include <asm/cpu-features.h> #include <asm/mipsregs.h> #include <asm/cpu-type.h> @@ -45,29 +49,54 @@ typedef unsigned int cycles_t; * However for now the implementaton of this function doesn't get these * fine details right. */ -static inline cycles_t get_cycles(void) +static inline int can_use_mips_counter(unsigned int prid) { - switch (boot_cpu_type()) { - case CPU_R4400PC: - case CPU_R4400SC: - case CPU_R4400MC: - if ((read_c0_prid() & 0xff) >= 0x0050) - return read_c0_count(); - break; + int comp = (prid & PRID_COMP_MASK) != PRID_COMP_LEGACY; - case CPU_R4000PC: - case CPU_R4000SC: - case CPU_R4000MC: - break; + if (__builtin_constant_p(cpu_has_counter) && !cpu_has_counter) + return 0; + else if (__builtin_constant_p(cpu_has_mips_r) && cpu_has_mips_r) + return 1; + else if (likely(!__builtin_constant_p(cpu_has_mips_r) && comp)) + return 1; + /* Make sure we don't peek at cpu_data[0].options in the fast path! */ + if (!__builtin_constant_p(cpu_has_counter)) + asm volatile("" : "=m" (cpu_data[0].options)); + if (likely(cpu_has_counter && + prid >= (PRID_IMP_R4000 | PRID_REV_ENCODE_44(5, 0)))) + return 1; + else + return 0; +} - default: - if (cpu_has_counter) - return read_c0_count(); - break; - } +static inline cycles_t get_cycles(void) +{ + if (can_use_mips_counter(read_c0_prid())) + return read_c0_count(); + else + return 0; /* no usable counter */ +} + +/* + * Like get_cycles - but where c0_count is not available we desperately + * use c0_random in an attempt to get at least a little bit of entropy. + * + * R6000 and R6000A neither have a count register nor a random register. + * That leaves no entropy source in the CPU itself. + */ +static inline unsigned long random_get_entropy(void) +{ + unsigned int prid = read_c0_prid(); + unsigned int imp = prid & PRID_IMP_MASK; - return 0; /* no usable counter */ + if (can_use_mips_counter(prid)) + return read_c0_count(); + else if (likely(imp != PRID_IMP_R6000 && imp != PRID_IMP_R6000A)) + return read_c0_random(); + else + return 0; /* no usable register */ } +#define random_get_entropy random_get_entropy #endif /* __KERNEL__ */ |