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Re: [PATCH v20 08/17] clocksource/drivers/arm_arch_timer: Rework counter frequency detection.

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Hi Mark, Christopher,

On 26 January 2017 at 01:36, Mark Rutland <mark.rutland@arm.com> wrote:
> On Wed, Jan 25, 2017 at 10:38:01AM -0500, Christopher Covington wrote:
>> On 01/25/2017 01:46 AM, Fu Wei wrote:
>> > On 25 January 2017 at 01:24, Mark Rutland <mark.rutland@arm.com> wrote:
>> >> On Wed, Jan 18, 2017 at 09:25:32PM +0800, fu.wei@linaro.org wrote:
>> >>> From: Fu Wei <fu.wei@linaro.org>
>
>> > And for CNTFRQ(in CNTCTLBase and CNTBaseN) , we can NOT access it in
>> > Linux kernel (EL1),
>> > Because ARMv8 ARM says:
>> > In a system that implements both Secure and Non-secure states, this
>> > register is only accessible by Secure accesses.
>> > That means we still need to get the frequency of the system counter
>> > from CNTFRQ_EL0 in MMIO timer code.
>> > This have been proved when I tested this driver on foundation model, I
>> > got "0" when I access CNTFRQ from Linux kernel (Non-secure EL1)
>>
>> That sounds like a firmware problem. Firmware in EL3 is supposed to write
>> the value into CNTFRQ.
>
> Definitely. FW *should* program the CNTFRQ_EL0 CPU registers and any
> MMIO CNTFRQ registers.

Many thanks for the explanation. This might be the problem. Maybe we
can check the UEFI :-)

>
>> If you're not currently using any firmware, I'd
>> recommend the bootwrapper on models/simulators/emulators.
>>
>> http://git.kernel.org/cgit/linux/kernel/git/mark/boot-wrapper-aarch64.git/tree/arch/aarch64/boot.S#n48
>
> Unfortunately, the boot-wrapper only programs the CNTFRQ_EL0 CPU system
> registers, and does not program any MMIO CNTFRQ registers.
>
> IIRC the models it was originally written for didn't have any (and we
> had no DT binding until far later...). Luckily the model DTs do not
> expose any MMIO timer addresses to the kernel currently.

But according to another document(ARMv8-A Foundation Platform User
Guide  ARM DUI0677K), Table 3-2 ARMv8-A Foundation Platform memory
map,
we may have two frames in the Generic timer block, right?


>
> Thanks,
> Mark.



-- 
Best regards,

Fu Wei
Software Engineer
Red Hat

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[PATCH v20 00/17] acpi, clocksource: add GTDT driver and GTDT support in arm_arch_timer fu.wei@linaro.org - 2017-01-18 14:30 +0100
  [PATCH v20 01/17] clocksource/drivers/arm_arch_timer: Improve printk relevant code fu.wei@linaro.org - 2017-01-18 14:30 +0100
  [PATCH v20 02/17] clocksource/drivers/arm_arch_timer: Rename the timer type macros. fu.wei@linaro.org - 2017-01-18 14:30 +0100
  [PATCH v20 06/17] clocksource/drivers/arm_arch_timer: rework PPI determination fu.wei@linaro.org - 2017-01-18 14:30 +0100
  [PATCH v20 12/17] clocksource/drivers/arm_arch_timer: Refactor MMIO timer probing. fu.wei@linaro.org - 2017-01-18 14:40 +0100
  [PATCH v20 16/17] clocksource/drivers/arm_arch_timer: Add GTDT support for memory-mapped timer fu.wei@linaro.org - 2017-01-18 14:40 +0100
    Re: [PATCH v20 16/17] clocksource/drivers/arm_arch_timer: Add GTDT  support for memory-mapped timer Hanjun Guo <hanjun.guo@linaro.org> - 2017-01-19 10:20 +0100
      Re: [PATCH v20 16/17] clocksource/drivers/arm_arch_timer: Add GTDT  support for memory-mapped timer Fu Wei <fu.wei@linaro.org> - 2017-01-19 11:10 +0100
        Re: [PATCH v20 16/17] clocksource/drivers/arm_arch_timer: Add GTDT  support for memory-mapped timer Hanjun Guo <hanjun.guo@linaro.org> - 2017-01-19 13:50 +0100
  [PATCH v20 11/17] clocksource/drivers/arm_arch_timer: Introduce some new structs to prepare for GTDT fu.wei@linaro.org - 2017-01-18 14:40 +0100
    Re: [PATCH v20 11/17] clocksource/drivers/arm_arch_timer: Introduce  some new structs to prepare for GTDT Hanjun Guo <hanjun.guo@linaro.org> - 2017-01-19 09:30 +0100
      Re: [PATCH v20 11/17] clocksource/drivers/arm_arch_timer: Introduce  some new structs to prepare for GTDT Fu Wei <fu.wei@linaro.org> - 2017-01-19 11:00 +0100
  [PATCH v20 07/17] clocksource/drivers/arm_arch_timer: Separate out device-tree code from arch_timer_detect_rate fu.wei@linaro.org - 2017-01-18 14:40 +0100
  [PATCH v20 09/17] clocksource/drivers/arm_arch_timer: Refactor arch_timer_needs_probing fu.wei@linaro.org - 2017-01-18 14:40 +0100
  [PATCH v20 13/17] acpi/arm64: Add GTDT table parse driver fu.wei@linaro.org - 2017-01-18 14:40 +0100
    Re: [PATCH v20 13/17] acpi/arm64: Add GTDT table parse driver Hanjun Guo <hanjun.guo@linaro.org> - 2017-01-19 10:20 +0100
      Re: [PATCH v20 13/17] acpi/arm64: Add GTDT table parse driver Fu Wei <fu.wei@linaro.org> - 2017-01-19 11:40 +0100
        Re: [PATCH v20 13/17] acpi/arm64: Add GTDT table parse driver Mark Rutland <mark.rutland@arm.com> - 2017-01-19 12:20 +0100
          Re: [PATCH v20 13/17] acpi/arm64: Add GTDT table parse driver Fu Wei <fu.wei@linaro.org> - 2017-01-19 13:30 +0100
  [PATCH v20 05/17] clocksource/drivers/arm_arch_timer: Add a new enum for spi type fu.wei@linaro.org - 2017-01-18 14:40 +0100
  [PATCH v20 08/17] clocksource/drivers/arm_arch_timer: Rework counter frequency detection. fu.wei@linaro.org - 2017-01-18 14:40 +0100
    Re: [PATCH v20 08/17] clocksource/drivers/arm_arch_timer: Rework  counter frequency detection. Hanjun Guo <hanjun.guo@linaro.org> - 2017-01-19 09:10 +0100
      Re: [PATCH v20 08/17] clocksource/drivers/arm_arch_timer: Rework  counter frequency detection. Fu Wei <fu.wei@linaro.org> - 2017-01-19 10:50 +0100
        Re: [PATCH v20 08/17] clocksource/drivers/arm_arch_timer: Rework  counter frequency detection. Hanjun Guo <hanjun.guo@linaro.org> - 2017-01-19 13:50 +0100
    Re: [PATCH v20 08/17] clocksource/drivers/arm_arch_timer: Rework  counter frequency detection. Mark Rutland <mark.rutland@arm.com> - 2017-01-24 18:30 +0100
      Re: [PATCH v20 08/17] clocksource/drivers/arm_arch_timer: Rework  counter frequency detection. Fu Wei <fu.wei@linaro.org> - 2017-01-25 07:50 +0100
        Re: [PATCH v20 08/17] clocksource/drivers/arm_arch_timer: Rework  counter frequency detection. Fu Wei <fu.wei@linaro.org> - 2017-01-25 08:30 +0100
        Re: [PATCH v20 08/17] clocksource/drivers/arm_arch_timer: Rework  counter frequency detection. Christopher Covington <cov@codeaurora.org> - 2017-01-25 16:40 +0100
          Re: [PATCH v20 08/17] clocksource/drivers/arm_arch_timer: Rework  counter frequency detection. Mark Rutland <mark.rutland@arm.com> - 2017-01-25 18:40 +0100
            Re: [PATCH v20 08/17] clocksource/drivers/arm_arch_timer: Rework  counter frequency detection. Fu Wei <fu.wei@linaro.org> - 2017-01-26 07:00 +0100
        Re: [PATCH v20 08/17] clocksource/drivers/arm_arch_timer: Rework  counter frequency detection. Mark Rutland <mark.rutland@arm.com> - 2017-01-25 18:30 +0100
          Re: [PATCH v20 08/17] clocksource/drivers/arm_arch_timer: Rework  counter frequency detection. Fu Wei <fu.wei@linaro.org> - 2017-01-26 06:50 +0100
            Re: [PATCH v20 08/17] clocksource/drivers/arm_arch_timer: Rework  counter frequency detection. Mark Rutland <mark.rutland@arm.com> - 2017-01-30 19:00 +0100
  [PATCH v20 10/17] clocksource/drivers/arm_arch_timer: Move arch_timer_needs_of_probing into DT init call fu.wei@linaro.org - 2017-01-18 14:40 +0100
  [PATCH v20 14/17] clocksource/drivers/arm_arch_timer: Simplify ACPI support code. fu.wei@linaro.org - 2017-01-18 14:40 +0100
  [PATCH v20 15/17] acpi/arm64: Add memory-mapped timer support in GTDT driver fu.wei@linaro.org - 2017-01-18 14:40 +0100
  [PATCH v20 17/17] acpi/arm64: Add SBSA Generic Watchdog support in GTDT driver fu.wei@linaro.org - 2017-01-18 14:50 +0100
  Re: [PATCH v20 00/17] acpi, clocksource: add GTDT driver and GTDT  support in arm_arch_timer Hanjun Guo <hanjun.guo@linaro.org> - 2017-01-19 10:30 +0100
    Re: [PATCH v20 00/17] acpi, clocksource: add GTDT driver and GTDT  support in arm_arch_timer Fu Wei <fu.wei@linaro.org> - 2017-01-19 12:20 +0100
  Re: [PATCH v20 00/17] acpi, clocksource: add GTDT driver and GTDT  support in arm_arch_timer Mark Rutland <mark.rutland@arm.com> - 2017-01-23 20:00 +0100
    Re: [PATCH v20 00/17] acpi, clocksource: add GTDT driver and GTDT  support in arm_arch_timer Fu Wei <fu.wei@linaro.org> - 2017-01-24 06:20 +0100

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