From: Keqian Zhu <zhukeqian1@huawei.com>
To: <linux-kernel@vger.kernel.org>,
<linux-arm-kernel@lists.infradead.org>,
<kvmarm@lists.cs.columbia.edu>, <kvm@vger.kernel.org>
Cc: Marc Zyngier <maz@kernel.org>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Thomas Gleixner <tglx@linutronix.de>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will@kernel.org>, James Morse <james.morse@arm.com>,
Suzuki K Poulose <suzuki.poulose@arm.com>,
"Sean Christopherson" <sean.j.christopherson@intel.com>,
Julien Thierry <julien.thierry.kdev@gmail.com>,
Mark Brown <broonie@kernel.org>,
"Andrew Morton" <akpm@linux-foundation.org>,
Alexios Zavras <alexios.zavras@intel.com>,
<wanghaibin.wang@huawei.com>, Keqian Zhu <zhukeqian1@huawei.com>
Subject: [PATCH v3 2/2] clocksource: arm_arch_timer: Correct fault programming of CNTKCTL_EL1.EVNTI
Date: Fri, 4 Dec 2020 15:31:26 +0800 [thread overview]
Message-ID: <20201204073126.6920-3-zhukeqian1@huawei.com> (raw)
In-Reply-To: <20201204073126.6920-1-zhukeqian1@huawei.com>
ARM virtual counter supports event stream, it can only trigger an event
when the trigger bit (the value of CNTKCTL_EL1.EVNTI) of CNTVCT_EL0 changes,
so the actual period of event stream is 2^(cntkctl_evnti + 1). For example,
when the trigger bit is 0, then virtual counter trigger an event for every
two cycles.
Fixes: 037f637767a8 ("drivers: clocksource: add support for ARM architected timer event stream")
Suggested-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Keqian Zhu <zhukeqian1@huawei.com>
---
drivers/clocksource/arm_arch_timer.c | 23 ++++++++++++++++-------
1 file changed, 16 insertions(+), 7 deletions(-)
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index 777d38cb39b0..d0177824c518 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -822,15 +822,24 @@ static void arch_timer_evtstrm_enable(int divider)
static void arch_timer_configure_evtstream(void)
{
- int evt_stream_div, pos;
+ int evt_stream_div, lsb;
+
+ /*
+ * As the event stream can at most be generated at half the frequency
+ * of the counter, use half the frequency when computing the divider.
+ */
+ evt_stream_div = arch_timer_rate / ARCH_TIMER_EVT_STREAM_FREQ / 2;
+
+ /*
+ * Find the closest power of two to the divisor. If the adjacent bit
+ * of lsb (last set bit, starts from 0) is set, then we use (lsb + 1).
+ */
+ lsb = fls(evt_stream_div) - 1;
+ if (lsb > 0 && (evt_stream_div & BIT(lsb - 1)))
+ lsb++;
- /* Find the closest power of two to the divisor */
- evt_stream_div = arch_timer_rate / ARCH_TIMER_EVT_STREAM_FREQ;
- pos = fls(evt_stream_div);
- if (pos > 1 && !(evt_stream_div & (1 << (pos - 2))))
- pos--;
/* enable event stream */
- arch_timer_evtstrm_enable(min(pos, 15));
+ arch_timer_evtstrm_enable(max(0, min(lsb, 15)));
}
static void arch_counter_set_user_access(void)
--
2.23.0
next prev parent reply other threads:[~2020-12-04 7:33 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-04 7:31 [PATCH v3 0/2] clocksource: arm_arch_timer: Some fixes Keqian Zhu
2020-12-04 7:31 ` [PATCH v3 1/2] clocksource: arm_arch_timer: Use stable count reader in erratum sne Keqian Zhu
2020-12-12 12:58 ` [tip: timers/core] clocksource/drivers/arm_arch_timer: " tip-bot2 for Keqian Zhu
2020-12-04 7:31 ` Keqian Zhu [this message]
2020-12-05 11:15 ` [PATCH v3 2/2] clocksource: arm_arch_timer: Correct fault programming of CNTKCTL_EL1.EVNTI Daniel Lezcano
2020-12-05 18:22 ` Marc Zyngier
2020-12-05 18:30 ` Daniel Lezcano
2020-12-12 12:58 ` [tip: timers/core] clocksource/drivers/arm_arch_timer: " tip-bot2 for Keqian Zhu
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