mips: Add clock_getres entry point

The generic vDSO library provides an implementation of clock_getres()
that can be leveraged by each architecture.

Add clock_getres() entry point on mips.

Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Paul Burton <paul.burton@mips.com>
Signed-off-by: Vincenzo Frascino <vincenzo.frascino@arm.com>
Signed-off-by: Paul Burton <paul.burton@mips.com>

arch/mips/include/asm/vdso/gettimeofday.h

@@ -22,6 +22,8 @@
 #include <asm/unistd.h>
 #include <asm/vdso.h>
 
+#define VDSO_HAS_CLOCK_GETRES		1
+
 #ifdef CONFIG_MIPS_CLOCK_VSYSCALL
 
 static __always_inline long gettimeofday_fallback(
@@ -79,6 +81,30 @@ static __always_inline long clock_gettime_fallback(
 	return error ? -ret : ret;
 }
 
+static __always_inline int clock_getres_fallback(
+					clockid_t _clkid,
+					struct __kernel_timespec *_ts)
+{
+	register struct __kernel_timespec *ts asm("a1") = _ts;
+	register clockid_t clkid asm("a0") = _clkid;
+	register long ret asm("v0");
+#if _MIPS_SIM == _MIPS_SIM_ABI64
+	register long nr asm("v0") = __NR_clock_getres;
+#else
+	register long nr asm("v0") = __NR_clock_getres_time64;
+#endif
+	register long error asm("a3");
+
+	asm volatile(
+	"       syscall\n"
+	: "=r" (ret), "=r" (error)
+	: "r" (clkid), "r" (ts), "r" (nr)
+	: "$1", "$3", "$8", "$9", "$10", "$11", "$12", "$13",
+	  "$14", "$15", "$24", "$25", "hi", "lo", "memory");
+
+	return error ? -ret : ret;
+}
+
 #ifdef CONFIG_CSRC_R4K
 
 static __always_inline u64 read_r4k_count(void)

arch/mips/vdso/vdso.lds.S

@@ -95,6 +95,7 @@ VERSION
 	global:
 		__vdso_clock_gettime;
 		__vdso_gettimeofday;
+		__vdso_clock_getres;
 #endif
 	local: *;
 	};

arch/mips/vdso/vgettimeofday.c

@@ -23,6 +23,12 @@ int __vdso_gettimeofday(struct __kernel_old_timeval *tv,
 	return __cvdso_gettimeofday(tv, tz);
 }
 
+int __vdso_clock_getres(clockid_t clock_id,
+			struct old_timespec32 *res)
+{
+	return __cvdso_clock_getres_time32(clock_id, res);
+}
+
 #else
 
 int __vdso_clock_gettime(clockid_t clock,
@@ -37,4 +43,10 @@ int __vdso_gettimeofday(struct __kernel_old_timeval *tv,
 	return __cvdso_gettimeofday(tv, tz);
 }
 
+int __vdso_clock_getres(clockid_t clock_id,
+			struct __kernel_timespec *res)
+{
+	return __cvdso_clock_getres(clock_id, res);
+}
+
 #endif