This is a bug fix for using physical arch timers when
the arch_timer_use_virtual boolean is false. It restores the
arch_counter_get_cntpct() function after removal in
0d651e4e "clocksource: arch_timer: use virtual counters"
We need this on certain ARMv7 systems which are architected like this:
* The firmware doesn't know and doesn't care about hypervisor mode and
we don't want to add the complexity of hypervisor there.
* The firmware isn't involved in SMP bringup or resume.
* The ARCH timer come up with an uninitialized offset between the
virtual and physical counters. Each core gets a different random
offset.
* The device boots in "Secure SVC" mode.
* Nothing has touched the reset value of CNTHCTL.PL1PCEN or
CNTHCTL.PL1PCTEN (both default to 1 at reset)
One example of such as system is RK3288 where it is much simpler to
use the physical counter since there's nobody managing the offset and
each time a core goes down and comes back up it will get reinitialized
to some other random value.
Fixes: 0d651e4e65e9 ("clocksource: arch_timer: use virtual counters")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Sonny Rao <sonnyrao@xxxxxxxxxxxx>
Acked-by: Olof Johansson <olof@xxxxxxxxx>
---
v2: Add fixes tag to commit message, cc stable, copy Doug's
description of the systems which need this in commit message.
v3: Don't change the memory-mapped physical timer/counter code
---
arch/arm/include/asm/arch_timer.h | 9 +++++++++
arch/arm64/include/asm/arch_timer.h | 10 ++++++++++
drivers/clocksource/arm_arch_timer.c | 25 ++++++++++++++++++++++---
3 files changed, 41 insertions(+), 3 deletions(-)
diff --git a/arch/arm/include/asm/arch_timer.h b/arch/arm/include/asm/arch_timer.h
index 0704e0c..e72aa4d 100644
--- a/arch/arm/include/asm/arch_timer.h
+++ b/arch/arm/include/asm/arch_timer.h
@@ -78,6 +78,15 @@ static inline u32 arch_timer_get_cntfrq(void)
return val;
}
+static inline u64 arch_counter_get_cntpct(void)
+{
+ u64 cval;
+
+ isb();
+ asm volatile("mrrc p15, 0, %Q0, %R0, c14" : "=r" (cval));
+ return cval;
+}
+
static inline u64 arch_counter_get_cntvct(void)
{
u64 cval;
diff --git a/arch/arm64/include/asm/arch_timer.h b/arch/arm64/include/asm/arch_timer.h
index 9400596..58657c4 100644
--- a/arch/arm64/include/asm/arch_timer.h
+++ b/arch/arm64/include/asm/arch_timer.h
@@ -135,6 +135,16 @@ static inline void arch_timer_evtstrm_enable(int divider)
#endif
}
+static inline u64 arch_counter_get_cntpct(void)
+{
+ u64 cval;
+
+ isb();
+ asm volatile("mrs %0, cntpct_el0" : "=r" (cval));
+
+ return cval;
+}
+
static inline u64 arch_counter_get_cntvct(void)
{
u64 cval;
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index 5163ec1..bd8da15 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -30,6 +30,8 @@
#define CNTTIDR 0x08
#define CNTTIDR_VIRT(n) (BIT(1) << ((n) * 4))
+#define CNTPCT_LO 0x00
+#define CNTPCT_HI 0x04
#define CNTVCT_LO 0x08
#define CNTVCT_HI 0x0c
#define CNTFRQ 0x10
@@ -386,6 +388,19 @@ static u64 arch_counter_get_cntvct_mem(void)
return ((u64) vct_hi << 32) | vct_lo;
}
+static u64 arch_counter_get_cntpct_mem(void)
+{
+ u32 pct_lo, pct_hi, tmp_hi;
+
+ do {
+ pct_hi = readl_relaxed(arch_counter_base + CNTPCT_HI);
+ pct_lo = readl_relaxed(arch_counter_base + CNTPCT_LO);
+ tmp_hi = readl_relaxed(arch_counter_base + CNTPCT_HI);
+ } while (pct_hi != tmp_hi);
+
+ return ((u64) pct_hi << 32) | pct_lo;
+}
+
/*
* Default to cp15 based access because arm64 uses this function for
* sched_clock() before DT is probed and the cp15 method is guaranteed
@@ -429,10 +444,14 @@ static void __init arch_counter_register(unsigned type)
u64 start_count;
/* Register the CP15 based counter if we have one */
- if (type & ARCH_CP15_TIMER)
- arch_timer_read_counter = arch_counter_get_cntvct;
- else
+ if (type & ARCH_CP15_TIMER) {
+ if (arch_timer_use_virtual)
+ arch_timer_read_counter = arch_counter_get_cntvct;
+ else
+ arch_timer_read_counter = arch_counter_get_cntpct;
+ } else {
arch_timer_read_counter = arch_counter_get_cntvct_mem;
+ }
start_count = arch_timer_read_counter();
clocksource_register_hz(&clocksource_counter, arch_timer_rate);
--
1.8.3.2
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