[PATCH v4 07/17] clocksource/arm_arch_timer: Move MMIO timer programming over to CVAL

Marc Zyngier
2021-10-17T12:43:23Z

Similarily to the sysreg-based timer, move the MMIO over to using
the CVAL registers instead of TVAL. Note that there is no warranty
that the 64bit MMIO access will be atomic, but the timer is always
disabled at the point where we program CVAL.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
arch/arm/include/asm/arch_timer.h | 1 +
drivers/clocksource/arm_arch_timer.c | 50 +++++++++++++++++++++-------
2 files changed, 39 insertions(+), 12 deletions(-)

diff --git a/arch/arm/include/asm/arch_timer.h b/arch/arm/include/asm/arch_timer.h
index a9b2b721c7f9..9f4b895b78f7 100644
--- a/arch/arm/include/asm/arch_timer.h
+++ b/arch/arm/include/asm/arch_timer.h
@@ -7,6 +7,7 @@
#include <asm/hwcap.h>
#include <linux/clocksource.h>
#include <linux/init.h>
+#include <linux/io-64-nonatomic-lo-hi.h>
#include <linux/types.h>

#include <clocksource/arm_arch_timer.h>
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index bede10f67f9a..f4db3a65bc79 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -44,11 +44,13 @@
#define CNTACR_RWVT BIT(4)
#define CNTACR_RWPT BIT(5)

-#define CNTVCT_LO 0x08
-#define CNTVCT_HI 0x0c
+#define CNTVCT_LO 0x00
+#define CNTPCT_LO 0x08
#define CNTFRQ 0x10
+#define CNTP_CVAL_LO 0x20
#define CNTP_TVAL 0x28
#define CNTP_CTL 0x2c
+#define CNTV_CVAL_LO 0x30
#define CNTV_TVAL 0x38
#define CNTV_CTL 0x3c

@@ -112,6 +114,13 @@ void arch_timer_reg_write(int access, enum arch_timer_reg reg, u64 val,
case ARCH_TIMER_REG_TVAL:
writel_relaxed((u32)val, timer->base + CNTP_TVAL);
break;
+ case ARCH_TIMER_REG_CVAL:
+ /*
+ * Not guaranteed to be atomic, so the timer
+ * must be disabled at this point.
+ */
+ writeq_relaxed(val, timer->base + CNTP_CVAL_LO);
+ break;
default:
BUILD_BUG();
}
@@ -124,6 +133,10 @@ void arch_timer_reg_write(int access, enum arch_timer_reg reg, u64 val,
case ARCH_TIMER_REG_TVAL:
writel_relaxed((u32)val, timer->base + CNTV_TVAL);
break;
+ case ARCH_TIMER_REG_CVAL:
+ /* Same restriction as above */
+ writeq_relaxed(val, timer->base + CNTV_CVAL_LO);
+ break;
default:
BUILD_BUG();
}
@@ -720,15 +733,36 @@ static int arch_timer_set_next_event_phys(unsigned long evt,
return 0;
}

+static u64 arch_counter_get_cnt_mem(struct arch_timer *t, int offset_lo)
+{
+ u32 cnt_lo, cnt_hi, tmp_hi;
+
+ do {
+ cnt_hi = readl_relaxed(t->base + offset_lo + 4);
+ cnt_lo = readl_relaxed(t->base + offset_lo);
+ tmp_hi = readl_relaxed(t->base + offset_lo + 4);
+ } while (cnt_hi != tmp_hi);
+
+ return ((u64) cnt_hi << 32) | cnt_lo;
+}
+
static __always_inline void set_next_event_mem(const int access, unsigned long evt,
struct clock_event_device *clk)
{
+ struct arch_timer *timer = to_arch_timer(clk);
unsigned long ctrl;
+ u64 cnt;
+
ctrl = arch_timer_reg_read(access, ARCH_TIMER_REG_CTRL, clk);
ctrl |= ARCH_TIMER_CTRL_ENABLE;
ctrl &= ~ARCH_TIMER_CTRL_IT_MASK;

- arch_timer_reg_write(access, ARCH_TIMER_REG_TVAL, evt, clk);
+ if (access == ARCH_TIMER_MEM_VIRT_ACCESS)
+ cnt = arch_counter_get_cnt_mem(timer, CNTVCT_LO);
+ else
+ cnt = arch_counter_get_cnt_mem(timer, CNTPCT_LO);
+
+ arch_timer_reg_write(access, ARCH_TIMER_REG_CVAL, evt + cnt, clk);
arch_timer_reg_write(access, ARCH_TIMER_REG_CTRL, ctrl, clk);
}

@@ -970,15 +1004,7 @@ bool arch_timer_evtstrm_available(void)

static u64 arch_counter_get_cntvct_mem(void)
{
- u32 vct_lo, vct_hi, tmp_hi;
-
- do {
- vct_hi = readl_relaxed(arch_timer_mem->base + CNTVCT_HI);
- vct_lo = readl_relaxed(arch_timer_mem->base + CNTVCT_LO);
- tmp_hi = readl_relaxed(arch_timer_mem->base + CNTVCT_HI);
- } while (vct_hi != tmp_hi);
-
- return ((u64) vct_hi << 32) | vct_lo;
+ return arch_counter_get_cnt_mem(arch_timer_mem, CNTVCT_LO);
}

static struct arch_timer_kvm_info arch_timer_kvm_info;
--
2.30.2