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From: Daniel Lezcano <daniel.lezcano@linaro.org>
To: tglx@linutronix.de
Cc: linux-kernel@vger.kernel.org, Marc Zyngier <marc.zyngier@arm.com>,
	Mark Rutland <mark.rutland@arm.com>,
	linux-arm-kernel@lists.infradead.org (moderated list:ARM
	ARCHITECTED TIMER DRIVER)
Subject: [PATCH 16/29] arm64: arch_timer: Workaround for Cortex-A73 erratum 858921
Date: Sun, 16 Apr 2017 22:27:06 +0200	[thread overview]
Message-ID: <1492374441-23336-16-git-send-email-daniel.lezcano@linaro.org> (raw)
In-Reply-To: <1492374441-23336-1-git-send-email-daniel.lezcano@linaro.org>

From: Marc Zyngier <marc.zyngier@arm.com>

Cortex-A73 (all versions) counter read can return a wrong value
when the counter crosses a 32bit boundary.

The workaround involves performing the read twice, and to return
one or the other depending on whether a transition has taken place.

Acked-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
---
 drivers/clocksource/Kconfig          | 11 +++++++++++
 drivers/clocksource/arm_arch_timer.c | 19 +++++++++++++++++++
 2 files changed, 30 insertions(+)

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 3356ab8..af80a7c 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -366,6 +366,17 @@ config HISILICON_ERRATUM_161010101
 	  161010101. The workaround will be active if the hisilicon,erratum-161010101
 	  property is found in the timer node.
 
+config ARM64_ERRATUM_858921
+	bool "Workaround for Cortex-A73 erratum 858921"
+	default y
+	select ARM_ARCH_TIMER_OOL_WORKAROUND
+	depends on ARM_ARCH_TIMER && ARM64
+	help
+	  This option enables a workaround applicable to Cortex-A73
+	  (all versions), whose counter may return incorrect values.
+	  The workaround will be dynamically enabled when an affected
+	  core is detected.
+
 config ARM_GLOBAL_TIMER
 	bool "Support for the ARM global timer" if COMPILE_TEST
 	select CLKSRC_OF if OF
diff --git a/drivers/clocksource/arm_arch_timer.c b/drivers/clocksource/arm_arch_timer.c
index f8adea2..8459d19 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -266,6 +266,17 @@ static u64 notrace hisi_161010101_read_cntvct_el0(void)
 }
 #endif
 
+#ifdef CONFIG_ARM64_ERRATUM_858921
+static u64 notrace arm64_858921_read_cntvct_el0(void)
+{
+	u64 old, new;
+
+	old = read_sysreg(cntvct_el0);
+	new = read_sysreg(cntvct_el0);
+	return (((old ^ new) >> 32) & 1) ? old : new;
+}
+#endif
+
 #ifdef CONFIG_ARM_ARCH_TIMER_OOL_WORKAROUND
 DEFINE_PER_CPU(const struct arch_timer_erratum_workaround *,
 	       timer_unstable_counter_workaround);
@@ -331,6 +342,14 @@ static const struct arch_timer_erratum_workaround ool_workarounds[] = {
 		.set_next_event_virt = erratum_set_next_event_tval_virt,
 	},
 #endif
+#ifdef CONFIG_ARM64_ERRATUM_858921
+	{
+		.match_type = ate_match_local_cap_id,
+		.id = (void *)ARM64_WORKAROUND_858921,
+		.desc = "ARM erratum 858921",
+		.read_cntvct_el0 = arm64_858921_read_cntvct_el0,
+	},
+#endif
 };
 
 typedef bool (*ate_match_fn_t)(const struct arch_timer_erratum_workaround *,
-- 
2.7.4

  parent reply	other threads:[~2017-04-16 20:28 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-04-16 20:25 [GIT PULL] timers changes for 4.12 Daniel Lezcano
2017-04-16 20:26 ` [PATCH 01/29] arm64: Allow checking of a CPU-local erratum Daniel Lezcano
2017-04-16 20:26   ` [PATCH 02/29] arm64: Add CNTVCT_EL0 trap handler Daniel Lezcano
2017-04-16 20:26   ` [PATCH 03/29] arm64: Define Cortex-A73 MIDR Daniel Lezcano
2017-04-16 20:26   ` [PATCH 04/29] arm64: cpu_errata: Allow an erratum to be match for all revisions of a core Daniel Lezcano
2017-04-16 20:26   ` [PATCH 05/29] arm64: cpu_errata: Add capability to advertise Cortex-A73 erratum 858921 Daniel Lezcano
2017-04-16 20:26   ` [PATCH 06/29] arm64: arch_timer: Add infrastructure for multiple erratum detection methods Daniel Lezcano
2017-04-16 20:26   ` [PATCH 07/29] arm64: arch_timer: Add erratum handler for CPU-specific capability Daniel Lezcano
2017-04-16 20:26   ` [PATCH 08/29] arm64: arch_timer: Move arch_timer_reg_read/write around Daniel Lezcano
2017-04-16 20:26   ` [PATCH 09/29] arm64: arch_timer: Get rid of erratum_workaround_set_sne Daniel Lezcano
2017-04-16 20:27   ` [PATCH 10/29] arm64: arch_timer: Rework the set_next_event workarounds Daniel Lezcano
2017-04-16 20:27   ` [PATCH 11/29] arm64: arch_timer: Make workaround methods optional Daniel Lezcano
2017-04-16 20:27   ` [PATCH 12/29] arm64: arch_timer: Allows a CPU-specific erratum to only affect a subset of CPUs Daniel Lezcano
2017-04-16 20:27   ` [PATCH 13/29] arm64: arch_timer: Move clocksource_counter and co around Daniel Lezcano
2017-04-16 20:27   ` [PATCH 14/29] arm64: arch_timer: Save cntkctl_el1 as a per-cpu variable Daniel Lezcano
2017-04-16 20:27   ` [PATCH 15/29] arm64: arch_timer: Enable CNTVCT_EL0 trap if workaround is enabled Daniel Lezcano
2017-04-16 20:27   ` Daniel Lezcano [this message]
2017-04-16 20:27   ` [PATCH 17/29] arm64: arch_timer: Allow erratum matching with ACPI OEM information Daniel Lezcano
2017-04-16 20:27   ` [PATCH 18/29] arm64: arch_timer: Add HISILICON_ERRATUM_161010101 ACPI matching data Daniel Lezcano
2017-04-16 20:27   ` [PATCH 19/29] clocksource/drivers/orion: Read clock rate once Daniel Lezcano
2017-04-16 20:27   ` [PATCH 20/29] clocksource/drivers/orion: Add delay_timer implementation Daniel Lezcano
2017-04-16 20:27   ` [PATCH 21/29] clocksource: Add missing line break to error messages Daniel Lezcano
2017-04-24  7:45     ` Uwe Kleine-König
2017-04-16 20:27   ` [PATCH 22/29] dt-bindings: Clarify compatible property for rockchip timers Daniel Lezcano
2017-04-20 14:12     ` Rob Herring
2017-04-16 20:27   ` [PATCH 23/29] ARM: dts: rockchip: Update compatible property for rk322x timer Daniel Lezcano
2017-04-16 20:27   ` [PATCH 24/29] clocksource/drivers/rockchip_timer: Implement clocksource timer Daniel Lezcano
2017-04-16 20:27   ` [PATCH 25/29] ARM: dts: rockchip: Add timer entries to rk3188 SoC Daniel Lezcano
2017-04-16 20:27   ` [PATCH 26/29] ARM: dts: rockchip: disable arm-global-timer for rk3188 Daniel Lezcano
2017-04-16 20:27   ` [PATCH 27/29] clocksource: Augment bindings for Faraday timer Daniel Lezcano
2017-04-16 20:27   ` [PATCH 28/29] clocksource/drivers/gemini: Rename Gemini timer to Faraday Daniel Lezcano
2017-04-16 20:27   ` [PATCH 29/29] clocksource/drivers/fttmr010: Refactor to handle clock Daniel Lezcano

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