[PATCH v8 3/4] arm64: arch_timer: Work around Erratum Hisilicon-161010101
Ding Tianhong
dingtianhong at huawei.com
Thu Jan 19 03:14:33 PST 2017
Erratum Hisilicon-161010101 says that the ARM generic timer counter "has the
potential to contain an erroneous value when the timer value changes".
Accesses to TVAL (both read and write) are also affected due to the implicit counter
read. Accesses to CVAL are not affected.
The workaround is to reread the system count registers until the value of the second
read is larger than the first one by less than 32, the system counter can be guaranteed
not to return wrong value twice by back-to-back read and the error value is always larger
than the correct one by 32. Writes to TVAL are replaced with an equivalent write to CVAL.
The hisilicon erratum CONFIG name is too long, breaking the line format in silicon-errata.txt,
so extended the character spacing to fit all the erratum config.
Signed-off-by: Ding Tianhong <dingtianhong at huawei.com>
---
Documentation/arm64/silicon-errata.txt | 43 ++++++++++++++---------------
drivers/clocksource/Kconfig | 12 ++++++++-
drivers/clocksource/arm_arch_timer.c | 49 ++++++++++++++++++++++++++++++++++
3 files changed, 82 insertions(+), 22 deletions(-)
diff --git a/Documentation/arm64/silicon-errata.txt b/Documentation/arm64/silicon-errata.txt
index 405da11..0aaae35 100644
--- a/Documentation/arm64/silicon-errata.txt
+++ b/Documentation/arm64/silicon-errata.txt
@@ -42,24 +42,25 @@ file acts as a registry of software workarounds in the Linux Kernel and
will be updated when new workarounds are committed and backported to
stable kernels.
-| Implementor | Component | Erratum ID | Kconfig |
-+----------------+-----------------+-----------------+-------------------------+
-| ARM | Cortex-A53 | #826319 | ARM64_ERRATUM_826319 |
-| ARM | Cortex-A53 | #827319 | ARM64_ERRATUM_827319 |
-| ARM | Cortex-A53 | #824069 | ARM64_ERRATUM_824069 |
-| ARM | Cortex-A53 | #819472 | ARM64_ERRATUM_819472 |
-| ARM | Cortex-A53 | #845719 | ARM64_ERRATUM_845719 |
-| ARM | Cortex-A53 | #843419 | ARM64_ERRATUM_843419 |
-| ARM | Cortex-A57 | #832075 | ARM64_ERRATUM_832075 |
-| ARM | Cortex-A57 | #852523 | N/A |
-| ARM | Cortex-A57 | #834220 | ARM64_ERRATUM_834220 |
-| ARM | Cortex-A72 | #853709 | N/A |
-| ARM | MMU-500 | #841119,#826419 | N/A |
-| | | | |
-| Cavium | ThunderX ITS | #22375, #24313 | CAVIUM_ERRATUM_22375 |
-| Cavium | ThunderX ITS | #23144 | CAVIUM_ERRATUM_23144 |
-| Cavium | ThunderX GICv3 | #23154 | CAVIUM_ERRATUM_23154 |
-| Cavium | ThunderX Core | #27456 | CAVIUM_ERRATUM_27456 |
-| Cavium | ThunderX SMMUv2 | #27704 | N/A |
-| | | | |
-| Freescale/NXP | LS2080A/LS1043A | A-008585 | FSL_ERRATUM_A008585 |
+| Implementor | Component | Erratum ID | Kconfig |
++----------------+-----------------+-----------------+---------------------------------+
+| ARM | Cortex-A53 | #826319 | ARM64_ERRATUM_826319 |
+| ARM | Cortex-A53 | #827319 | ARM64_ERRATUM_827319 |
+| ARM | Cortex-A53 | #824069 | ARM64_ERRATUM_824069 |
+| ARM | Cortex-A53 | #819472 | ARM64_ERRATUM_819472 |
+| ARM | Cortex-A53 | #845719 | ARM64_ERRATUM_845719 |
+| ARM | Cortex-A53 | #843419 | ARM64_ERRATUM_843419 |
+| ARM | Cortex-A57 | #832075 | ARM64_ERRATUM_832075 |
+| ARM | Cortex-A57 | #852523 | N/A |
+| ARM | Cortex-A57 | #834220 | ARM64_ERRATUM_834220 |
+| ARM | Cortex-A72 | #853709 | N/A |
+| ARM | MMU-500 | #841119,#826419 | N/A |
+| | | | |
+| Cavium | ThunderX ITS | #22375, #24313 | CAVIUM_ERRATUM_22375 |
+| Cavium | ThunderX ITS | #23144 | CAVIUM_ERRATUM_23144 |
+| Cavium | ThunderX GICv3 | #23154 | CAVIUM_ERRATUM_23154 |
+| Cavium | ThunderX Core | #27456 | CAVIUM_ERRATUM_27456 |
+| Cavium | ThunderX SMMUv2 | #27704 | N/A |
+| | | | |
+| Freescale/NXP | LS2080A/LS1043A | A-008585 | FSL_ERRATUM_A008585 |
+| Hisilicon | Hip0{5,6,7} | #161010101 | HISILICON_ERRATUM_161010101 |
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index 04c2b93..628cb44 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -327,7 +327,7 @@ config ARM_ARCH_TIMER_EVTSTREAM
config ARM_ARCH_TIMER_OOL_WORKAROUND
bool "Workaround for arm arch timer unstable counter"
- depends on FSL_ERRATUM_A008585
+ depends on FSL_ERRATUM_A008585 || HISILICON_ERRATUM_161010101
help
This option would only be enabled by Freescale/NXP Erratum A-008585
or something else chip has similar erratum.
@@ -343,6 +343,16 @@ config FSL_ERRATUM_A008585
value"). The workaround will only be active if the
fsl,erratum-a008585 property is found in the timer node.
+config HISILICON_ERRATUM_161010101
+ bool "Workaround for Hisilicon Erratum 161010101"
+ default y
+ select ARM_ARCH_TIMER_OOL_WORKAROUND
+ depends on ARM_ARCH_TIMER && ARM64
+ help
+ This option enables a workaround for Hisilicon Erratum
+ 161010101. The workaround will be active if the hisilicon,erratum-161010101
+ property is found in the timer node.
+
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 2487c66..7451b62 100644
--- a/drivers/clocksource/arm_arch_timer.c
+++ b/drivers/clocksource/arm_arch_timer.c
@@ -131,6 +131,47 @@ static u64 notrace fsl_a008585_read_cntvct_el0(void)
}
#endif
+#ifdef CONFIG_HISILICON_ERRATUM_161010101
+/*
+ * Verify whether the value of the second read is larger than the first by
+ * less than 32 is the only way to confirm the value is correct, so clear the
+ * lower 5 bits to check whether the difference is greater than 32 or not.
+ * Theoretically the erratum should not occur more than twice in succession
+ * when reading the system counter, but it is possible that some interrupts
+ * may lead to more than twice read errors, triggering the warning, so setting
+ * the number of retries far beyond the number of iterations the loop has been
+ * observed to take.
+ */
+#define __hisi_161010101_read_reg(reg) ({ \
+ u64 _old, _new; \
+ int _retries = 50; \
+ \
+ do { \
+ _old = read_sysreg(reg); \
+ _new = read_sysreg(reg); \
+ _retries--; \
+ } while (unlikely((_new - _old) >> 5) && _retries); \
+ \
+ WARN_ON_ONCE(!_retries); \
+ _new; \
+})
+
+static u32 notrace hisi_161010101_read_cntp_tval_el0(void)
+{
+ return __hisi_161010101_read_reg(cntp_tval_el0);
+}
+
+static u32 notrace hisi_161010101_read_cntv_tval_el0(void)
+{
+ return __hisi_161010101_read_reg(cntv_tval_el0);
+}
+
+static u64 notrace hisi_161010101_read_cntvct_el0(void)
+{
+ return __hisi_161010101_read_reg(cntvct_el0);
+}
+#endif
+
#ifdef CONFIG_ARM_ARCH_TIMER_OOL_WORKAROUND
const struct arch_timer_erratum_workaround *timer_unstable_counter_workaround = NULL;
EXPORT_SYMBOL_GPL(timer_unstable_counter_workaround);
@@ -147,6 +188,14 @@ static u64 notrace fsl_a008585_read_cntvct_el0(void)
.read_cntvct_el0 = fsl_a008585_read_cntvct_el0,
},
#endif
+#ifdef CONFIG_HISILICON_ERRATUM_161010101
+ {
+ .id = "hisilicon,erratum-161010101",
+ .read_cntp_tval_el0 = hisi_161010101_read_cntp_tval_el0,
+ .read_cntv_tval_el0 = hisi_161010101_read_cntv_tval_el0,
+ .read_cntvct_el0 = hisi_161010101_read_cntvct_el0,
+ },
+#endif
};
#endif /* CONFIG_ARM_ARCH_TIMER_OOL_WORKAROUND */
--
1.9.0
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