[PATCH v7 0/4] arm64: arch_timer: Add workaround for hisilicon-161601 erratum

[Ding Tianhong]

Hi Marc:

How about this v7, if any suggestions very grateful.

Thanks.
Ding

On 2017/1/7 15:07, Ding Tianhong wrote:
> Erratum Hisilicon-161601 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.
> 
> v2: Introducing a new generic erratum handling mechanism for fsl,a008585 and hisilicon,161601.
>     Significant rework based on feedback, including seperate the fsl erratum a008585
>     to another patch, update the erratum name and remove unwanted code.
> 
> v3: Introducing the erratum_workaround_set_sne generic function for fsl erratum a008585
>     and make the #define __fsl_a008585_read_reg to be private to the .c file instead of
>     being globally visible. After discussion with Marc and Will, a consensus decision was
>     made to remove the commandline parameter for enabling fsl,erratum-a008585 erratum,
>     and make some generic name more specific, export timer_unstable_counter_workaround
>     for module access.
>     
>     Significant rework based on feedback, including fix some alignment problem, make the
>     #define __hisi_161601_read_reg to be private to the .c file instead of being globally
>     visible, add more accurate annotation and modify a bit of logical format to enable
>     arch_timer_read_ool_enabled, remove the kernel commandline parameter
>     clocksource.arm_arch_timer.hisilicon-161601.
> 
>     Introduce a generic aquick framework for erratum in ACPI mode.
> 
> v4: rename the quirk handler parameter to make it more generic, and
>     avoid break loop when handling the quirk becasue it need to
>     support multi quirks handler.
> 
>     update some data structures for acpi mode. 
> 
> v5: Adapt the new kernel-parameters.txt for latest kernel version.
>     Set the retries of reread system counter to 50, because it is possible 
>     that some interrupts may lead to more than twice read errors and break the loop,
>     it will trigger the warning, so we set the number of retries far beyond the number of
>     iterations the loop has been observed to take.
> 
> v6: The last 2 patches in the previous version about the ACPI mode will conflict witch Fuwei's
>     GTDT patches, so remove the ACPI part and only support the DT base code for this patch set.
> 
>     We have trigger a bug when select the CONFIG_FUNCTION_GRAPH_TRACER and enable function_graph
>     to /sys/kernel/debug/tracing/current_tracer, the system will stall into an endless loop, it looks
>     like that the ftrace_graph_caller will be related to xxx.read_cntvct_el0 and read the system counter
>     again, so mark the xxx.read_cntvct_el0 with notrace to fix the problem.
> 
> v7: Introduce a new general config symbol named CONFIG_ARM_ARCH_TIMER_OOL_WORKAROUND to enable the workaround
>     for any chips which has similar arch timer erratum just like "fsl,erratum_a008585" and "hisilicon,erratum_161601",
>     modify the struct arch_timer_erratum_workaround to be compatible different chip erratum more easily, and
>     reconstruction some code base on the new config symbol and struct, thanks to Marc's suggestion. 
> 
> Ding Tianhong (4):
>   arm64: arch_timer: Add device tree binding for hisilicon-161601
>     erratum
>   arm64: arch_timer: Introduce a generic erratum handing mechanism for
>     fsl-a008585
>   arm64: arch_timer: Work around Erratum Hisilicon-161601
>   arm64: arch timer: Add timer erratum property for Hip05-d02 and
>     Hip06-d03
> 
>  Documentation/admin-guide/kernel-parameters.txt    |   9 --
>  Documentation/arm64/silicon-errata.txt             |   1 +
>  .../devicetree/bindings/arm/arch_timer.txt         |   8 ++
>  arch/arm64/boot/dts/hisilicon/hip05.dtsi           |   1 +
>  arch/arm64/boot/dts/hisilicon/hip06.dtsi           |   1 +
>  arch/arm64/include/asm/arch_timer.h                |  38 ++----
>  drivers/clocksource/Kconfig                        |  18 +++
>  drivers/clocksource/arm_arch_timer.c               | 150 +++++++++++++++------
>  8 files changed, 152 insertions(+), 74 deletions(-)
>