@@ -5,25 +5,25 @@ HTE Kernel provider driver
55
66Description
77-----------
8- The Nvidia tegra194 HTE provider driver implements two GTE
9- (Generic Timestamping Engine) instances: 1) GPIO GTE and 2) LIC
10- (Legacy Interrupt Controller) IRQ GTE. Both GTE instances get the
11- timestamp from the system counter TSC which has 31.25MHz clock rate, and the
12- driver converts clock tick rate to nanoseconds before storing it as timestamp
13- value.
8+ The Nvidia tegra HTE provider also known as GTE (Generic Timestamping Engine)
9+ driver implements two GTE instances: 1) GPIO GTE and 2) LIC
10+ (Legacy Interrupt Controller) IRQ GTE. Both GTE instances get the timestamp
11+ from the system counter TSC which has 31.25MHz clock rate, and the driver
12+ converts clock tick rate to nanoseconds before storing it as timestamp value.
1413
1514GPIO GTE
1615--------
1716
1817This GTE instance timestamps GPIO in real time. For that to happen GPIO
19- needs to be configured as input. The always on (AON) GPIO controller instance
20- supports timestamping GPIOs in real time and it has 39 GPIO lines. The GPIO GTE
21- and AON GPIO controller are tightly coupled as it requires very specific bits
22- to be set in GPIO config register before GPIO GTE can be used, for that GPIOLIB
23- adds two optional APIs as below. The GPIO GTE code supports both kernel
24- and userspace consumers. The kernel space consumers can directly talk to HTE
25- subsystem while userspace consumers timestamp requests go through GPIOLIB CDEV
26- framework to HTE subsystem.
18+ needs to be configured as input. Only the always on (AON) GPIO controller
19+ instance supports timestamping GPIOs in real time as it is tightly coupled with
20+ the GPIO GTE. To support this, GPIOLIB adds two optional APIs as mentioned
21+ below. The GPIO GTE code supports both kernel and userspace consumers. The
22+ kernel space consumers can directly talk to HTE subsystem while userspace
23+ consumers timestamp requests go through GPIOLIB CDEV framework to HTE
24+ subsystem. The hte devicetree binding described at
25+ ``Documentation/devicetree/bindings/timestamp `` provides an example of how a
26+ consumer can request an GPIO line.
2727
2828See gpiod_enable_hw_timestamp_ns() and gpiod_disable_hw_timestamp_ns().
2929
@@ -34,9 +34,8 @@ returns the timestamp in nanoseconds.
3434LIC (Legacy Interrupt Controller) IRQ GTE
3535-----------------------------------------
3636
37- This GTE instance timestamps LIC IRQ lines in real time. There are 352 IRQ
38- lines which this instance can add timestamps to in real time. The hte
39- devicetree binding described at ``Documentation/devicetree/bindings/timestamp ``
37+ This GTE instance timestamps LIC IRQ lines in real time. The hte devicetree
38+ binding described at ``Documentation/devicetree/bindings/timestamp ``
4039provides an example of how a consumer can request an IRQ line. Since it is a
4140one-to-one mapping with IRQ GTE provider, consumers can simply specify the IRQ
4241number that they are interested in. There is no userspace consumer support for
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