1 .. SPDX-License-Identifier: GPL-2.0+
2
3 HTE Kernel provider driver
4 ==========================
5
6 Description
7 -----------
8 The Nvidia tegra HTE provider also known as GT
9 driver implements two GTE instances: 1) GPIO G
10 (Legacy Interrupt Controller) IRQ GTE. Both GT
11 from the system counter TSC which has 31.25MHz
12 converts clock tick rate to nanoseconds before
13
14 GPIO GTE
15 --------
16
17 This GTE instance timestamps GPIO in real time
18 needs to be configured as input. Only the alwa
19 instance supports timestamping GPIOs in real t
20 the GPIO GTE. To support this, GPIOLIB adds tw
21 below. The GPIO GTE code supports both kernel
22 kernel space consumers can directly talk to HT
23 consumers timestamp requests go through GPIOLI
24 subsystem. The hte devicetree binding describe
25 ``Documentation/devicetree/bindings/timestamp`
26 consumer can request an GPIO line.
27
28 See gpiod_enable_hw_timestamp_ns() and gpiod_d
29
30 For userspace consumers, GPIO_V2_LINE_FLAG_EVE
31 specified during IOCTL calls. Refer to ``tools
32 returns the timestamp in nanoseconds.
33
34 LIC (Legacy Interrupt Controller) IRQ GTE
35 -----------------------------------------
36
37 This GTE instance timestamps LIC IRQ lines in
38 binding described at ``Documentation/devicetre
39 provides an example of how a consumer can requ
40 one-to-one mapping with IRQ GTE provider, cons
41 number that they are interested in. There is n
42 this GTE instance in the HTE framework.
43
44 The provider source code of both IRQ and GPIO
45 ``drivers/hte/hte-tegra194.c``. The test drive
46 ``drivers/hte/hte-tegra194-test.c`` demonstrat
47 and GPIO GTE.
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