[RFC 3/6] arm/arm64: clocksource: Introduce vclock_mode

[Boqun Feng <boqun.feng@gmail.com>]

Similar to x86, use a vclock_mode in arch_clocksource_data to differ
clocksoures use different read function in vDSO.

No functional changes, only preparation for support vDSO in ARM64 on
Hyper-V.

Note: the changes for arm are only because arm and arm64 share the same
code in the arch timer driver and require arch_clocksource_data having
the same field.

Signed-off-by: Boqun Feng (Microsoft) <boqun.feng@gmail.com>
---
 arch/arm/include/asm/clocksource.h                | 6 +++++-
 arch/arm/kernel/vdso.c                            | 1 -
 arch/arm64/include/asm/clocksource.h              | 6 +++++-
 arch/arm64/include/asm/mshyperv.h                 | 2 +-
 arch/arm64/include/asm/vdso/compat_gettimeofday.h | 5 +++--
 arch/arm64/include/asm/vdso/gettimeofday.h        | 5 +++--
 arch/arm64/include/asm/vdso/vsyscall.h            | 4 +---
 drivers/clocksource/arm_arch_timer.c              | 8 ++++----
 8 files changed, 22 insertions(+), 15 deletions(-)

diff --git a/arch/arm/include/asm/clocksource.h b/arch/arm/include/asm/clocksource.h
index 0b350a7e26f3..017c5ab6e587 100644
--- a/arch/arm/include/asm/clocksource.h
+++ b/arch/arm/include/asm/clocksource.h
@@ -1,8 +1,12 @@
 #ifndef _ASM_CLOCKSOURCE_H
 #define _ASM_CLOCKSOURCE_H
 
+#define VCLOCK_NONE	0	/* No vDSO clock available.		*/
+#define VCLOCK_CNTVCT	1	/* vDSO should use cntvcnt		*/
+#define VCLOCK_MAX	1
+
 struct arch_clocksource_data {
-	bool vdso_direct;	/* Usable for direct VDSO access? */
+	int vclock_mode;
 };
 
 #endif
diff --git a/arch/arm/kernel/vdso.c b/arch/arm/kernel/vdso.c
index c89ac1b9d28b..09e46ec420fe 100644
--- a/arch/arm/kernel/vdso.c
+++ b/arch/arm/kernel/vdso.c
@@ -263,4 +263,3 @@ void arm_install_vdso(struct mm_struct *mm, unsigned long addr)
 	if (!IS_ERR(vma))
 		mm->context.vdso = addr;
 }
-
diff --git a/arch/arm64/include/asm/clocksource.h b/arch/arm64/include/asm/clocksource.h
index 0ece64a26c8c..fbe80057468c 100644
--- a/arch/arm64/include/asm/clocksource.h
+++ b/arch/arm64/include/asm/clocksource.h
@@ -2,8 +2,12 @@
 #ifndef _ASM_CLOCKSOURCE_H
 #define _ASM_CLOCKSOURCE_H
 
+#define VCLOCK_NONE	0	/* No vDSO clock available.		*/
+#define VCLOCK_CNTVCT	1	/* vDSO should use cntvcnt		*/
+#define VCLOCK_MAX	1
+
 struct arch_clocksource_data {
-	bool vdso_direct;	/* Usable for direct VDSO access? */
+	int vclock_mode;
 };
 
 #endif
diff --git a/arch/arm64/include/asm/mshyperv.h b/arch/arm64/include/asm/mshyperv.h
index 9cc4aeddf2d0..0afb00e3501d 100644
--- a/arch/arm64/include/asm/mshyperv.h
+++ b/arch/arm64/include/asm/mshyperv.h
@@ -90,7 +90,7 @@ extern void hv_get_vpreg_128(u32 reg, struct hv_get_vp_register_output *result);
 #define hv_set_reference_tsc(val) \
 		hv_set_vpreg(HV_REGISTER_REFERENCE_TSC, val)
 #define hv_set_clocksource_vdso(val) \
-		((val).archdata.vdso_direct = false)
+		((val).archdata.vclock_mode = VCLOCK_NONE)
 
 #if IS_ENABLED(CONFIG_HYPERV)
 #define hv_enable_stimer0_percpu_irq(irq)	enable_percpu_irq(irq, 0)
diff --git a/arch/arm64/include/asm/vdso/compat_gettimeofday.h b/arch/arm64/include/asm/vdso/compat_gettimeofday.h
index c50ee1b7d5cd..630d04c3c92e 100644
--- a/arch/arm64/include/asm/vdso/compat_gettimeofday.h
+++ b/arch/arm64/include/asm/vdso/compat_gettimeofday.h
@@ -8,6 +8,7 @@
 #ifndef __ASSEMBLY__
 
 #include <asm/unistd.h>
+#include <asm/clocksource.h>
 #include <uapi/linux/time.h>
 
 #include <asm/vdso/compat_barrier.h>
@@ -117,10 +118,10 @@ static __always_inline u64 __arch_get_hw_counter(s32 clock_mode)
 	u64 res;
 
 	/*
-	 * clock_mode == 0 implies that vDSO are enabled otherwise
+	 * clock_mode == VCLOCK_NONE implies that vDSO are disabled so
 	 * fallback on syscall.
 	 */
-	if (clock_mode)
+	if (clock_mode == VCLOCK_NONE)
 		return __VDSO_USE_SYSCALL;
 
 	/*
diff --git a/arch/arm64/include/asm/vdso/gettimeofday.h b/arch/arm64/include/asm/vdso/gettimeofday.h
index b08f476b72b4..e6e3fe0488c7 100644
--- a/arch/arm64/include/asm/vdso/gettimeofday.h
+++ b/arch/arm64/include/asm/vdso/gettimeofday.h
@@ -8,6 +8,7 @@
 #ifndef __ASSEMBLY__
 
 #include <asm/unistd.h>
+#include <asm/clocksource.h>
 #include <uapi/linux/time.h>
 
 #define __VDSO_USE_SYSCALL		ULLONG_MAX
@@ -71,10 +72,10 @@ static __always_inline u64 __arch_get_hw_counter(s32 clock_mode)
 	u64 res;
 
 	/*
-	 * clock_mode == 0 implies that vDSO are enabled otherwise
+	 * clock_mode == VCLOCK_NONE implies that vDSO are disabled so
 	 * fallback on syscall.
 	 */
-	if (clock_mode)
+	if (clock_mode == VCLOCK_NONE)
 		return __VDSO_USE_SYSCALL;
 
 	/*
diff --git a/arch/arm64/include/asm/vdso/vsyscall.h b/arch/arm64/include/asm/vdso/vsyscall.h
index 0c20a7c1bee5..07f78b0da498 100644
--- a/arch/arm64/include/asm/vdso/vsyscall.h
+++ b/arch/arm64/include/asm/vdso/vsyscall.h
@@ -24,9 +24,7 @@ struct vdso_data *__arm64_get_k_vdso_data(void)
 static __always_inline
 int __arm64_get_clock_mode(struct timekeeper *tk)
 {
-	u32 use_syscall = !tk->tkr_mono.clock->archdata.vdso_direct;
-
-	return use_syscall;
+	return tk->tkr_mono.clock->archdata.vclock_mode;
 }
 #define __arch_get_clock_mode __arm64_get_clock_mode
 
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index 9a5464c625b4..9b8d4d00b53b 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -69,7 +69,7 @@ static enum arch_timer_ppi_nr arch_timer_uses_ppi = ARCH_TIMER_VIRT_PPI;
 static bool arch_timer_c3stop;
 static bool arch_timer_mem_use_virtual;
 static bool arch_counter_suspend_stop;
-static bool vdso_default = true;
+static int vdso_default = VCLOCK_CNTVCT;
 
 static cpumask_t evtstrm_available = CPU_MASK_NONE;
 static bool evtstrm_enable = IS_ENABLED(CONFIG_ARM_ARCH_TIMER_EVTSTREAM);
@@ -560,8 +560,8 @@ void arch_timer_enable_workaround(const struct arch_timer_erratum_workaround *wa
 	 * change both the default value and the vdso itself.
 	 */
 	if (wa->read_cntvct_el0) {
-		clocksource_counter.archdata.vdso_direct = false;
-		vdso_default = false;
+		clocksource_counter.archdata.vclock_mode = VCLOCK_NONE;
+		vdso_default = VCLOCK_NONE;
 	}
 }
 
@@ -979,7 +979,7 @@ static void __init arch_counter_register(unsigned type)
 		}
 
 		arch_timer_read_counter = rd;
-		clocksource_counter.archdata.vdso_direct = vdso_default;
+		clocksource_counter.archdata.vclock_mode = vdso_default;
 	} else {
 		arch_timer_read_counter = arch_counter_get_cntvct_mem;
 	}
-- 
2.24.0