[PATCH v4 02/20] arm64: Implement arch_counter_get_cntpct to read the physical counter

Christoffer Dall
2017-10-20T11:48:40Z

As we are about to use the physical counter on arm64 systems that have
KVM support, implement arch_counter_get_cntpct() and the associated
errata workaround functionality for stable timer reads.

Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
---

Notes:
Changes since v3:
- Factored out this change into a separate patch

arch/arm64/include/asm/arch_timer.h | 8 +++-----
drivers/clocksource/arm_arch_timer.c | 23 +++++++++++++++++++++++
2 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h
index a652ce0a5cb2..04275de614db 100644
--- a/arch/arm64/include/asm/arch_timer.h
+++ b/arch/arm64/include/asm/arch_timer.h
@@ -52,6 +52,7 @@ struct arch_timer_erratum_workaround {
const char *desc;
u32 (*read_cntp_tval_el0)(void);
u32 (*read_cntv_tval_el0)(void);
+ u64 (*read_cntpct_el0)(void);
u64 (*read_cntvct_el0)(void);
int (*set_next_event_phys)(unsigned long, struct clock_event_device *);
int (*set_next_event_virt)(unsigned long, struct clock_event_device *);
@@ -148,11 +149,8 @@ static inline void arch_timer_set_cntkctl(u32 cntkctl)

static inline u64 arch_counter_get_cntpct(void)
{
- /*
- * AArch64 kernel and user space mandate the use of CNTVCT.
- */
- BUG();
- return 0;
+ isb();
+ return arch_timer_reg_read_stable(cntpct_el0);
}

static inline u64 arch_counter_get_cntvct(void)
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index fd4b7f684bd0..ff8f8a177156 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -217,6 +217,11 @@ static u32 notrace fsl_a008585_read_cntv_tval_el0(void)
return __fsl_a008585_read_reg(cntv_tval_el0);
}

+static u64 notrace fsl_a008585_read_cntpct_el0(void)
+{
+ return __fsl_a008585_read_reg(cntpct_el0);
+}
+
static u64 notrace fsl_a008585_read_cntvct_el0(void)
{
return __fsl_a008585_read_reg(cntvct_el0);
@@ -258,6 +263,11 @@ static u32 notrace hisi_161010101_read_cntv_tval_el0(void)
return __hisi_161010101_read_reg(cntv_tval_el0);
}

+static u64 notrace hisi_161010101_read_cntpct_el0(void)
+{
+ return __hisi_161010101_read_reg(cntpct_el0);
+}
+
static u64 notrace hisi_161010101_read_cntvct_el0(void)
{
return __hisi_161010101_read_reg(cntvct_el0);
@@ -288,6 +298,15 @@ static struct ate_acpi_oem_info hisi_161010101_oem_info[] = {
#endif

#ifdef CONFIG_ARM64_ERRATUM_858921
+static u64 notrace arm64_858921_read_cntpct_el0(void)
+{
+ u64 old, new;
+
+ old = read_sysreg(cntpct_el0);
+ new = read_sysreg(cntpct_el0);
+ return (((old ^ new) >> 32) & 1) ? old : new;
+}
+
static u64 notrace arm64_858921_read_cntvct_el0(void)
{
u64 old, new;
@@ -346,6 +365,7 @@ static const struct arch_timer_erratum_workaround ool_workarounds[] = {
.desc = "Freescale erratum a005858",
.read_cntp_tval_el0 = fsl_a008585_read_cntp_tval_el0,
.read_cntv_tval_el0 = fsl_a008585_read_cntv_tval_el0,
+ .read_cntpct_el0 = fsl_a008585_read_cntpct_el0,
.read_cntvct_el0 = fsl_a008585_read_cntvct_el0,
.set_next_event_phys = erratum_set_next_event_tval_phys,
.set_next_event_virt = erratum_set_next_event_tval_virt,
@@ -358,6 +378,7 @@ static const struct arch_timer_erratum_workaround ool_workarounds[] = {
.desc = "HiSilicon erratum 161010101",
.read_cntp_tval_el0 = hisi_161010101_read_cntp_tval_el0,
.read_cntv_tval_el0 = hisi_161010101_read_cntv_tval_el0,
+ .read_cntpct_el0 = hisi_161010101_read_cntpct_el0,
.read_cntvct_el0 = hisi_161010101_read_cntvct_el0,
.set_next_event_phys = erratum_set_next_event_tval_phys,
.set_next_event_virt = erratum_set_next_event_tval_virt,
@@ -368,6 +389,7 @@ static const struct arch_timer_erratum_workaround ool_workarounds[] = {
.desc = "HiSilicon erratum 161010101",
.read_cntp_tval_el0 = hisi_161010101_read_cntp_tval_el0,
.read_cntv_tval_el0 = hisi_161010101_read_cntv_tval_el0,
+ .read_cntpct_el0 = hisi_161010101_read_cntpct_el0,
.read_cntvct_el0 = hisi_161010101_read_cntvct_el0,
.set_next_event_phys = erratum_set_next_event_tval_phys,
.set_next_event_virt = erratum_set_next_event_tval_virt,
@@ -378,6 +400,7 @@ static const struct arch_timer_erratum_workaround ool_workarounds[] = {
.match_type = ate_match_local_cap_id,
.id = (void *)ARM64_WORKAROUND_858921,
.desc = "ARM erratum 858921",
+ .read_cntpct_el0 = arm64_858921_read_cntpct_el0,
.read_cntvct_el0 = arm64_858921_read_cntvct_el0,
},
#endif
--
2.14.2