linux-kernel - Re: [PATCH V4 06/10] hte: Re-phrase tegra API document

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Date:   Wed, 5 Apr 2023 17:03:36 -0700
From:   Dipen Patel <dipenp@...dia.com>
To:     Bagas Sanjaya <bagasdotme@...il.com>, thierry.reding@...il.com,
        jonathanh@...dia.com, linux-kernel@...r.kernel.org,
        linux-tegra@...r.kernel.org, linux-gpio@...r.kernel.org,
        linus.walleij@...aro.org, devicetree@...r.kernel.org,
        linux-doc@...r.kernel.org, robh+dt@...nel.org,
        timestamp@...ts.linux.dev, krzysztof.kozlowski+dt@...aro.org,
        brgl@...ev.pl, corbet@....net, gregkh@...uxfoundation.org
Subject: Re: [PATCH V4 06/10] hte: Re-phrase tegra API document

On 4/4/23 7:24 PM, Bagas Sanjaya wrote:
> On 3/23/23 08:29, Dipen Patel wrote:
>> Make Tegra194 API document generic to make it applicable for
>> current and future tegra hte providers.
>>
>> Signed-off-by: Dipen Patel <dipenp@...dia.com>
>> ---
>>  Documentation/driver-api/hte/tegra194-hte.rst | 33 +++++++++----------
>>  1 file changed, 16 insertions(+), 17 deletions(-)
>>
> 
> While generalizing the doc, the doc file name should also be renamed
> (i.e. to tegra-hte.rst).

make sense, I will do rename it in the next patch series.
> 
>> 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
> 
> The wording LGTM, thanks!
> 
> Reviewed-by: Bagas Sanjaya <bagasdotme@...il.com>
>