ARM Memory-Mapped Architected Timer

요약·해설과 원문, 전문 번역을 서로 분리했습니다. API 이름, symbol, source path는 원문 표기를 사용합니다.

1. 요약·해설

원문의 핵심 논리와 kernel programming 관점의 보충 설명입니다. 아래의 전문 번역과는 별도로 작성했습니다.

요약과 해설

arm,arch_timer_mmio.yaml:1-123

ARM memory-mapped timer의 control frame, view와 physical·virtual IRQ를 설명합니다. 접을 수 있는 영어 원문 전체와 한국어 전문 번역을 함께 제공하며 register, interrupt, clock, phandle, erratum, 수치와 줄 좌표를 원형대로 보존합니다.

2. 영어 원문 전체

번역 기준이 된 Linux v6.18.37 원문입니다. 줄 번호는 이 버전의 파일 좌표입니다.

원문 전체 펼치기

1 # SPDX-License-Identifier: GPL-2.0

2 %YAML 1.2

3 ---

4 $id: http://devicetree.org/schemas/timer/arm,arch_timer_mmio.yaml#

5 $schema: http://devicetree.org/meta-schemas/core.yaml#

7 title: ARM memory mapped architected timer

9 maintainers:

10 - Marc Zyngier <marc.zyngier@arm.com>

11 - Mark Rutland <mark.rutland@arm.com>

13 description: |+

14 ARM cores may have a memory mapped architected timer, which provides up to 8

15 frames with a physical and optional virtual timer per frame.

17 The memory mapped timer is attached to a GIC to deliver its interrupts via SPIs.

19 properties:

20 compatible:

21 items:

22 - enum:

23 - arm,armv7-timer-mem

25 reg:

26 maxItems: 1

27 description: The control frame base address

29 '#address-cells':

30 enum: [1, 2]

32 '#size-cells':

33 const: 1

35 ranges: true

37 clock-frequency:

38 description: The frequency of the main counter, in Hz. Should be present

39 only where necessary to work around broken firmware which does not configure

40 CNTFRQ on all CPUs to a uniform correct value. Use of this property is

41 strongly discouraged; fix your firmware unless absolutely impossible.

43 always-on:

44 type: boolean

45 description: If present, the timer is powered through an always-on power

46 domain, therefore it never loses context.

48 arm,cpu-registers-not-fw-configured:

49 type: boolean

50 description: Firmware does not initialize any of the generic timer CPU

51 registers, which contain their architecturally-defined reset values. Only

52 supported for 32-bit systems which follow the ARMv7 architected reset

53 values.

55 arm,no-tick-in-suspend:

56 type: boolean

57 description: The main counter does not tick when the system is in

58 low-power system suspend on some SoCs. This behavior does not match the

59 Architecture Reference Manual's specification that the system counter "must

60 be implemented in an always-on power domain."

62 patternProperties:

63 '^frame@[0-9a-f]+$':

64 type: object

65 additionalProperties: false

66 description: A timer node has up to 8 frame sub-nodes, each with the following properties.

67 properties:

68 frame-number:

69 $ref: /schemas/types.yaml#/definitions/uint32

70 minimum: 0

71 maximum: 7

73 interrupts:

74 minItems: 1

75 items:

76 - description: physical timer irq

77 - description: virtual timer irq

79 reg:

80 minItems: 1

81 items:

82 - description: 1st view base address

83 - description: 2nd optional view base address

85 required:

86 - frame-number

87 - interrupts

88 - reg

90 required:

91 - compatible

92 - reg

93 - '#address-cells'

94 - '#size-cells'

96 additionalProperties: false

98 examples:

99 - |

100 timer@f0000000 {

101 compatible = "arm,armv7-timer-mem";

102 #address-cells = <1>;

103 #size-cells = <1>;

104 ranges = <0 0xf0001000 0x1000>;

105 reg = <0xf0000000 0x1000>;

106 clock-frequency = <50000000>;

107

108 frame@0 {

109 frame-number = <0>;

110 interrupts = <0 13 0x8>,

111 <0 14 0x8>;

112 reg = <0x0000 0x1000>,

113 <0x1000 0x1000>;

114 };

115

116 frame@2000 {

117 frame-number = <1>;

118 interrupts = <0 15 0x8>;

119 reg = <0x2000 0x1000>;

120 };

121 };

122

123 ...

124

3. 한국어 전문 번역

영어 원문의 문단 순서와 의미를 유지한 전체 번역입니다. 코드, 함수명, symbol과 URL은 원문 표기를 유지합니다.

1-18

GPL-2.0 라이선스의 이 스키마는 ARM memory-mapped architected timer를 정의합니다. Timer는 최대 8개 frame을 제공하며 각 frame에는 physical timer와 선택적인 virtual timer가 있습니다. Memory-mapped timer는 GIC에 연결되어 SPI로 interrupt를 전달합니다. Maintainer는 Marc Zyngier와 Mark Rutland입니다.

Control frame과 firmware 우회 속성

19-61

Compatible은 `arm,armv7-timer-mem`입니다. `reg`는 control frame base address 한 항목이고 `#address-cells`는 1 또는 2, `#size-cells`는 1이며 `ranges`를 사용합니다. `clock-frequency`는 main counter 주파수를 Hz로 지정하지만, firmware가 모든 CPU의 `CNTFRQ`를 동일하고 올바른 값으로 설정하지 못하는 경우에만 필요합니다. 사용은 강하게 권장되지 않으며 가능하면 firmware를 고쳐야 합니다.

`always-on`은 timer가 always-on power domain에서 동작해 context를 잃지 않음을 뜻합니다. `arm,cpu-registers-not-fw-configured`는 firmware가 generic timer CPU register를 초기화하지 않았음을 나타내며 ARMv7 architected reset value를 따르는 32-bit system에서만 지원됩니다. `arm,no-tick-in-suspend`는 일부 SoC에서 low-power system suspend 중 main counter가 멈춘다는 뜻이며, system counter가 always-on power domain에 있어야 한다는 Architecture Reference Manual 명세와 일치하지 않습니다.

properties:
  compatible:
    items:
      - enum:
          - arm,armv7-timer-mem

  reg:
    maxItems: 1
    description: The control frame base address

  '#address-cells':
    enum: [1, 2]

  '#size-cells':
    const: 1

  ranges: true

  clock-frequency:
    description: The frequency of the main counter, in Hz. Should be present
      only where necessary to work around broken firmware which does not configure
      CNTFRQ on all CPUs to a uniform correct value. Use of this property is
      strongly discouraged; fix your firmware unless absolutely impossible.

  always-on:
    type: boolean
    description: If present, the timer is powered through an always-on power
      domain, therefore it never loses context.

  arm,cpu-registers-not-fw-configured:
    type: boolean
    description: Firmware does not initialize any of the generic timer CPU
      registers, which contain their architecturally-defined reset values. Only
      supported for 32-bit systems which follow the ARMv7 architected reset
      values.

  arm,no-tick-in-suspend:
    type: boolean
    description: The main counter does not tick when the system is in
      low-power system suspend on some SoCs. This behavior does not match the
      Architecture Reference Manual's specification that the system counter "must
      be implemented in an always-on power domain."

Frame 번호, IRQ와 view

62-97

`frame@[0-9a-f]+` 하위 node는 최대 8개입니다. `frame-number`는 0부터 7이고, `interrupts`는 physical timer IRQ 뒤에 선택적인 virtual timer IRQ가 옵니다. `reg`는 first view base address 뒤에 선택적인 second view base address가 옵니다. 각 frame에는 `frame-number`, `interrupts`, `reg`가 필수입니다. 상위 node에는 `compatible`, `reg`, `#address-cells`, `#size-cells`가 필요하며 추가 속성은 허용되지 않습니다.

patternProperties:
  '^frame@[0-9a-f]+$':
    type: object
    additionalProperties: false
    description: A timer node has up to 8 frame sub-nodes, each with the following properties.
    properties:
      frame-number:
        $ref: /schemas/types.yaml#/definitions/uint32
        minimum: 0
        maximum: 7

      interrupts:
        minItems: 1
        items:
          - description: physical timer irq
          - description: virtual timer irq

      reg:
        minItems: 1
        items:
          - description: 1st view base address
          - description: 2nd optional view base address

    required:
      - frame-number
      - interrupts
      - reg

required:
  - compatible
  - reg
  - '#address-cells'
  - '#size-cells'

additionalProperties: false

50MHz timer와 frame 0

98-115

예제 상위 timer는 control frame `0xf0000000`, frame window `0xf0001000`, main counter 50000000Hz를 지정합니다. `frame@0`은 frame number 0, physical IRQ 13과 virtual IRQ 14, 그리고 `0x0000`·`0x1000`의 두 view를 갖습니다.

- |
  timer@f0000000 {
    compatible = "arm,armv7-timer-mem";
    #address-cells = <1>;
    #size-cells = <1>;
    ranges = <0 0xf0001000 0x1000>;
    reg = <0xf0000000 0x1000>;
    clock-frequency = <50000000>;

    frame@0 {
      frame-number = <0>;
      interrupts = <0 13 0x8>,
             <0 14 0x8>;
      reg = <0x0000 0x1000>,
            <0x1000 0x1000>;
    };

단일 view frame 1

116-123

`frame@2000`은 frame number 1이며 physical IRQ 15 하나와 `0x2000`의 단일 view만 지정합니다. Virtual timer IRQ와 second view는 선택 사항이므로 생략됩니다.

      frame@2000 {
        frame-number = <1>;
        interrupts = <0 15 0x8>;
        reg = <0x2000 0x1000>;
      };
    };

...