Make Tegra194 API document generic to make it applicable for current and future tegra hte providers. Signed-off-by: Dipen Patel <dipenp@xxxxxxxxxx> --- Documentation/driver-api/hte/tegra194-hte.rst | 33 +++++++++---------- 1 file changed, 16 insertions(+), 17 deletions(-) diff --git a/Documentation/driver-api/hte/tegra194-hte.rst b/Documentation/driver-api/hte/tegra194-hte.rst index f2d617265546..85e654772782 100644 --- a/Documentation/driver-api/hte/tegra194-hte.rst +++ b/Documentation/driver-api/hte/tegra194-hte.rst @@ -5,25 +5,25 @@ HTE Kernel provider driver Description ----------- -The Nvidia tegra194 HTE provider driver implements two GTE -(Generic Timestamping Engine) instances: 1) GPIO GTE and 2) LIC -(Legacy Interrupt Controller) IRQ GTE. Both GTE instances get the -timestamp from the system counter TSC which has 31.25MHz clock rate, and the -driver converts clock tick rate to nanoseconds before storing it as timestamp -value. +The Nvidia tegra HTE provider also known as GTE (Generic Timestamping Engine) +driver implements two GTE instances: 1) GPIO GTE and 2) LIC +(Legacy Interrupt Controller) IRQ GTE. Both GTE instances get the timestamp +from the system counter TSC which has 31.25MHz clock rate, and the driver +converts clock tick rate to nanoseconds before storing it as timestamp value. GPIO GTE -------- This GTE instance timestamps GPIO in real time. For that to happen GPIO -needs to be configured as input. The always on (AON) GPIO controller instance -supports timestamping GPIOs in real time and it has 39 GPIO lines. The GPIO GTE -and AON GPIO controller are tightly coupled as it requires very specific bits -to be set in GPIO config register before GPIO GTE can be used, for that GPIOLIB -adds two optional APIs as below. The GPIO GTE code supports both kernel -and userspace consumers. The kernel space consumers can directly talk to HTE -subsystem while userspace consumers timestamp requests go through GPIOLIB CDEV -framework to HTE subsystem. +needs to be configured as input. Only the always on (AON) GPIO controller +instance supports timestamping GPIOs in real time as it is tightly coupled with +the GPIO GTE. To support this, GPIOLIB adds two optional APIs as mentioned +below. The GPIO GTE code supports both kernel and userspace consumers. The +kernel space consumers can directly talk to HTE subsystem while userspace +consumers timestamp requests go through GPIOLIB CDEV framework to HTE +subsystem. The hte devicetree binding described at +``Documentation/devicetree/bindings/timestamp`` provides an example of how a +consumer can request an GPIO line. See gpiod_enable_hw_timestamp_ns() and gpiod_disable_hw_timestamp_ns(). @@ -34,9 +34,8 @@ returns the timestamp in nanoseconds. LIC (Legacy Interrupt Controller) IRQ GTE ----------------------------------------- -This GTE instance timestamps LIC IRQ lines in real time. There are 352 IRQ -lines which this instance can add timestamps to in real time. The hte -devicetree binding described at ``Documentation/devicetree/bindings/timestamp`` +This GTE instance timestamps LIC IRQ lines in real time. The hte devicetree +binding described at ``Documentation/devicetree/bindings/timestamp`` provides an example of how a consumer can request an IRQ line. Since it is a one-to-one mapping with IRQ GTE provider, consumers can simply specify the IRQ number that they are interested in. There is no userspace consumer support for -- 2.17.1
