[PATCH v9 3/4] arm64: arch_timer: Work around Erratum Hisilicon-161010101
Daniel Lezcano
daniel.lezcano at linaro.org
Mon Jan 30 15:17:30 PST 2017
On Thu, Jan 19, 2017 at 09:35:15PM +0800, Ding Tianhong wrote:
> 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.
Line length.
> 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 6693e07..b30f44f 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
> - depends on FSL_ERRATUM_A008585
> + depends on FSL_ERRATUM_A008585 || HISILICON_ERRATUM_161010101
Same comment as the previous patch, this dependency is pointless.
Isn't possible to rely on the __init data mechanism, instead of polluting the
Kconfig with more options ?
> 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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