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SubjectRe: [patch v25 4/4] Documentation: jtag: Add ABI documentation
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On 05/29/2018 07:53 AM, Oleksandr Shamray wrote:
> Added document that describe the ABI for JTAG class drivrer

Sorry, there are still a few typos. Please see below.

> ---
> Documentation/ABI/testing/gpio-cdev | 1 -
> Documentation/ABI/testing/jtag-dev | 23 +++++++
> Documentation/jtag/overview | 27 +++++++++
> Documentation/jtag/transactions | 109 +++++++++++++++++++++++++++++++++++
> MAINTAINERS | 1 +
> 5 files changed, 160 insertions(+), 1 deletions(-)
> create mode 100644 Documentation/ABI/testing/jtag-dev
> create mode 100644 Documentation/jtag/overview
> create mode 100644 Documentation/jtag/transactions
>

> diff --git a/Documentation/jtag/overview b/Documentation/jtag/overview
> new file mode 100644
> index 0000000..f179095
> --- /dev/null
> +++ b/Documentation/jtag/overview
> @@ -0,0 +1,27 @@
> +Linux kernel JTAG support
> +=========================
> +
> +JTAG is an industry standard for verifying hardware.JTAG provides access to

needs space:
hardware. JTAG provides

> +many logic signals of a complex integrated circuit, including the device pins.
> +
> +A JTAG interface is a special interface added to a chip.
> +Depending on the version of JTAG, two, four, or five pins are added.
> +
> +The connector pins are:
> + TDI (Test Data In)
> + TDO (Test Data Out)
> + TCK (Test Clock)
> + TMS (Test Mode Select)
> + TRST (Test Reset) optional
> +
> +JTAG interface is designed to have two parts - basic core driver and
> +hardware specific driver. The basic driver introduces a general interface
> +which is not dependent of specific hardware. It provides communication
> +between user space and hardware specific driver.
> +Each JTAG device is represented as a char device from (jtag0, jtag1, ...).
> +Access to a JTAG device is performed through IOCTL calls.
> +
> +Call flow example:
> +User: open -> /dev/jatgX
> +User: ioctl -> /dev/jtagX -> JTAG core driver -> JTAG hardware specific driver
> +User: close -> /dev/jatgX

> diff --git a/Documentation/jtag/transactions b/Documentation/jtag/transactions
> new file mode 100644
> index 0000000..c5176a7
> --- /dev/null
> +++ b/Documentation/jtag/transactions
> @@ -0,0 +1,109 @@
> +The JTAG API
> +=============
> +
> +JTAG master devices can be accessed through a character misc-device.
> +Each JTAG master interface can be accessed by using /dev/jtagN.
> +
> +JTAG system calls set:
> +- SIR (Scan Instruction Register, IEEE 1149.1 Instruction Register scan);
> +- SDR (Scan Data Register, IEEE 1149.1 Data Register scan);
> +- RUNTEST (Forces the IEEE 1149.1 bus to a run state for a specified
> +number of clocks.
> +
> +open(), close()
> +-------
> +open() opens JTAG device.
> +
> +Open/Close device:
> +- jtag_fd = open("/dev/jtag0", O_RDWR);
> +- close(jtag_fd);
> +
> +ioctl()
> +-------
> +All access operations to JTAG devices are erformed through ioctl interface.

performed

> +The IOCTL interface supports these requests:
> + JTAG_IOCRUNTEST - Force JTAG state machine to RUN_TEST/IDLE state
> + JTAG_SIOCFREQ - Set JTAG TCK frequency
> + JTAG_GIOCFREQ - Get JTAG TCK frequency
> + JTAG_IOCXFER - send JTAG data Xfer
> + JTAG_GIOCSTATUS - get current JTAG TAP status
> + JTAG_SIOCMODE - set JTAG mode flags.



--
~Randy

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