[PATCH v29 4/6] Documentation: jtag: Add ABI documentation

[Ernesto Corona]

Added document that describe the ABI for JTAG class driver

Signed-off-by: Oleksandr Shamray <oleksandrs@xxxxxxxxxxxx>
Signed-off-by: Ernesto Corona <ernesto.corona@xxxxxxxxx>
Acked-by: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Jonathan Corbet <corbet@xxxxxxx>
Cc: Arnd Bergmann <arnd@xxxxxxxx>
Cc: Mauro Carvalho Chehab <mchehab+samsung@xxxxxxxxxx>
Cc: Linus Walleij <linus.walleij@xxxxxxxxxx>
Cc: Manivannan Sadhasivam <manivannan.sadhasivam@xxxxxxxxxx>
Cc: Jeffrey Hugo <jhugo@xxxxxxxxxxxxxx>
Cc: Steven Filary <steven.a.filary@xxxxxxxxx>
Cc: Jiri Pirko <jiri@xxxxxxxxxxxx>
Cc: Vadim Pasternak <vadimp@xxxxxxxxxxxx>
Cc: Amithash Prasad <amithash@xxxxxx>
Cc: Patrick Williams <patrickw3@xxxxxx>
Cc: Rgrs <rgrs@xxxxxxxxxxxxxx>
---
v28->v29
- Change ABI documentation to reStructuredText (rst) format.

v27->v28
Comments pointed by Steven Filary <steven.a.filary@xxxxxxxxx>
- Replace JTAG_IOCRUNTEST with JTAG_SIOCSTATE adding support for all TAPC
   end states in SW mode using a lookup table to navigate across states.
- Add support for simultaneous READ/WRITE transfers(JTAG_READ_WRITE_XFER).
- Support for switching JTAG controller mode between slave and master
  mode.
- Setup JTAG controller mode to master only when the driver is opened,
  letting other HW to own the JTAG bus when it isn't in use.
- Include JTAG bit bang IOCTL for low level JTAG control usage
  (JTAG_IOCBITBANG).

v26->v27
v25->v26
Comments pointed by Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
- fix spell in ABI documentation

v24->v25
Comments pointed by Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>
- Fixed documentation according to new open() behavior

v23->v24
v22->v23
Comments pointed by Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
- fix spell in ABI doccumentation

v21->v22
Comments pointed by Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
- fix spell in ABI doccumentation

v20->v21
Comments pointed by Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
- Fix JTAG dirver help in Kconfig

v19->v20
Comments pointed by Randy Dunlap <rdunlap@xxxxxxxxxxxxx>
- Fix JTAG doccumentation

v18->v19
Pavel Machek <pavel@xxxxxx>
- Added JTAG doccumentation to Documentation/jtag

v17->v18
v16->v17
v15->v16
v14->v15
v13->v14
v12->v13
v11->v12 Tobias Klauser <tklauser@xxxxxxxxxx>
Comments pointed by
- rename /Documentation/ABI/testing/jatg-dev -> jtag-dev
- Typo: s/interfase/interface
v10->v11
v9->v10
Fixes added by Oleksandr:
- change jtag-cdev to jtag-dev in documentation
- update KernelVersion and Date in jtag-dev documentation;
v8->v9
v7->v8
v6->v7
Comments pointed by Pavel Machek <pavel@xxxxxx>
- Added jtag-cdev documentation to Documentation/ABI/testing folder
---
 Documentation/ABI/testing/jtag-dev  |  23 ++++
 Documentation/index.rst             |   1 +
 Documentation/jtag/index.rst        |  18 +++
 Documentation/jtag/jtag-summary.rst |  47 +++++++
 Documentation/jtag/jtagdev.rst      | 194 ++++++++++++++++++++++++++++
 5 files changed, 283 insertions(+)
 create mode 100644 Documentation/ABI/testing/jtag-dev
 create mode 100644 Documentation/jtag/index.rst
 create mode 100644 Documentation/jtag/jtag-summary.rst
 create mode 100644 Documentation/jtag/jtagdev.rst

diff --git a/Documentation/ABI/testing/jtag-dev b/Documentation/ABI/testing/jtag-dev
new file mode 100644
index 000000000000..423baab18761
--- /dev/null
+++ b/Documentation/ABI/testing/jtag-dev
@@ -0,0 +1,23 @@
+What:		/dev/jtag[0-9]+
+Date:		July 2018
+KernelVersion:	4.20
+Contact:	oleksandrs@xxxxxxxxxxxx
+Description:
+		The misc device files /dev/jtag* are the interface
+		between JTAG master interface and userspace.
+
+		The ioctl(2)-based ABI is defined and documented in
+		[include/uapi]<linux/jtag.h>.
+
+		The following file operations are supported:
+
+		open(2)
+		Opens and allocates file descriptor.
+
+		ioctl(2)
+		Initiate various actions.
+		See the inline documentation in [include/uapi]<linux/jtag.h>
+		for descriptions of all ioctls.
+
+Users:
+		userspace tools which wants to access to JTAG bus
diff --git a/Documentation/index.rst b/Documentation/index.rst
index 9599c0f3eea8..f75e8fa17d0e 100644
--- a/Documentation/index.rst
+++ b/Documentation/index.rst
@@ -108,6 +108,7 @@ needed).
    iio/index
    isdn/index
    infiniband/index
+   jtag/index
    leds/index
    media/index
    netlabel/index
diff --git a/Documentation/jtag/index.rst b/Documentation/jtag/index.rst
new file mode 100644
index 000000000000..8a2761d1c17e
--- /dev/null
+++ b/Documentation/jtag/index.rst
@@ -0,0 +1,18 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==============================
+Joint Test Action Group (JTAG)
+==============================
+
+.. toctree::
+   :maxdepth: 1
+
+   jtag-summary
+   jtagdev
+
+.. only::  subproject and html
+
+   Indices
+   =======
+
+   * :ref:`genindex`
diff --git a/Documentation/jtag/jtag-summary.rst b/Documentation/jtag/jtag-summary.rst
new file mode 100644
index 000000000000..7d3211be9096
--- /dev/null
+++ b/Documentation/jtag/jtag-summary.rst
@@ -0,0 +1,47 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+====================================
+Linux kernel JTAG support
+====================================
+
+Introduction to JTAG
+====================
+
+JTAG is an industry standard for verifying hardware. JTAG provides access to
+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 -> JTAG core driver -> JTAG hardware specific driver
+	User: ioctl -> /dev/jtagX -> JTAG core driver -> JTAG hardware specific driver
+	User: close -> /dev/jatgX -> JTAG core driver -> JTAG hardware specific driver
+
+
+THANKS TO
+---------
+Contributors to Linux-JTAG discussions include (in alphabetical order,
+by last name):
+
+- Ernesto Corona
+- Jiri Pirko
+- Oleksandr Shamray
+- Steven Filary
+- Vadim Pasternak
diff --git a/Documentation/jtag/jtagdev.rst b/Documentation/jtag/jtagdev.rst
new file mode 100644
index 000000000000..445f0b9c5b4d
--- /dev/null
+++ b/Documentation/jtag/jtagdev.rst
@@ -0,0 +1,194 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+==================
+JTAG userspace 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/Close  device:
+::
+
+	jtag_fd = open("/dev/jtag0", O_RDWR);
+	close(jtag_fd);
+
+ioctl()
+-------
+All access operations to JTAG devices are performed through ioctl interface.
+The IOCTL interface supports these requests:
+::
+
+	JTAG_SIOCSTATE - Force JTAG state machine to go into a TAPC state
+	JTAG_SIOCFREQ - Set JTAG TCK frequency
+	JTAG_GIOCFREQ - Get JTAG TCK frequency
+	JTAG_IOCXFER - send/receive JTAG data Xfer
+	JTAG_GIOCSTATUS - get current JTAG TAP state
+	JTAG_SIOCMODE - set JTAG mode flags.
+	JTAG_IOCBITBANG - JTAG bitbang low level control.
+
+JTAG_SIOCFREQ
+~~~~~~~~~~~~~
+Set JTAG clock speed:
+::
+
+	unsigned int jtag_fd;
+	ioctl(jtag_fd, JTAG_SIOCFREQ, &frq);
+
+JTAG_GIOCFREQ
+~~~~~~~~~~~~~
+Get JTAG clock speed:
+::
+
+	unsigned int jtag_fd;
+	ioctl(jtag_fd, JTAG_GIOCFREQ, &frq);
+
+JTAG_SIOCSTATE
+~~~~~~~~~~~~~~
+Force JTAG state machine to go into a TAPC state
+::
+
+	struct jtag_end_tap_state {
+		__u8	reset;
+		__u8	endstate;
+		__u8	tck;
+	};
+
+reset: one of below options
+::
+
+	JTAG_NO_RESET - go through selected endstate from current state
+	JTAG_FORCE_RESET - go through TEST_LOGIC/RESET state before selected endstate
+
+endstate: any state listed in jtag_endstate enum
+::
+
+	enum jtag_endstate {
+		JTAG_STATE_TLRESET,
+		JTAG_STATE_IDLE,
+		JTAG_STATE_SELECTDR,
+		JTAG_STATE_CAPTUREDR,
+		JTAG_STATE_SHIFTDR,
+		JTAG_STATE_EXIT1DR,
+		JTAG_STATE_PAUSEDR,
+		JTAG_STATE_EXIT2DR,
+		JTAG_STATE_UPDATEDR,
+		JTAG_STATE_SELECTIR,
+		JTAG_STATE_CAPTUREIR,
+		JTAG_STATE_SHIFTIR,
+		JTAG_STATE_EXIT1IR,
+		JTAG_STATE_PAUSEIR,
+		JTAG_STATE_EXIT2IR,
+		JTAG_STATE_UPDATEIR
+	};
+
+tck: clock counter
+
+Example:
+::
+
+	struct jtag_end_tap_state end_state;
+
+	end_state.endstate = JTAG_STATE_IDLE;
+	end_state.reset = 0;
+	end_state.tck = data_p->tck;
+	usleep(25 * 1000);
+	ioctl(jtag_fd, JTAG_SIOCSTATE, &end_state);
+
+JTAG_GIOCSTATUS
+~~~~~~~~~~~~~~~
+Get JTAG TAPC current machine state
+::
+
+	unsigned int jtag_fd;
+	jtag_endstate endstate;
+	ioctl(jtag_fd, JTAG_GIOCSTATUS, &endstate);
+
+JTAG_IOCXFER
+~~~~~~~~~~~~
+Send SDR/SIR transaction
+::
+
+	struct jtag_xfer {
+		__u8	type;
+		__u8	direction;
+		__u8	endstate;
+		__u8	padding;
+		__u32	length;
+		__u64	tdio;
+	};
+
+type: transfer type - JTAG_SIR_XFER/JTAG_SDR_XFER
+
+direction: xfer direction - JTAG_READ_XFER/JTAG_WRITE_XFER/JTAG_READ_WRITE_XFER
+
+length: xfer data length in bits
+
+tdio : xfer data array
+
+endstate: end state after transaction finish any of jtag_endstate enum
+
+Example:
+::
+
+	struct jtag_xfer xfer;
+	static char buf[64];
+	static unsigned int buf_len = 0;
+	[...]
+	xfer.type = JTAG_SDR_XFER;
+	xfer.tdio = (__u64)buf;
+	xfer.length = buf_len;
+	xfer.endstate = JTAG_STATE_IDLE;
+
+	if (is_read)
+		xfer.direction = JTAG_READ_XFER;
+	else if (is_write)
+		xfer.direction = JTAG_WRITE_XFER;
+	else
+		xfer.direction = JTAG_READ_WRITE_XFER;
+
+	ioctl(jtag_fd, JTAG_IOCXFER, &xfer);
+
+JTAG_SIOCMODE
+~~~~~~~~~~~~~
+If hardware driver can support different running modes you can change it.
+
+Example:
+::
+
+	struct jtag_mode mode;
+	mode.feature = JTAG_XFER_MODE;
+	mode.mode = JTAG_XFER_HW_MODE;
+	ioctl(jtag_fd, JTAG_SIOCMODE, &mode);
+
+JTAG_IOCBITBANG
+~~~~~~~~~~~~~~~
+JTAG Bitbang low level operation.
+
+Example:
+::
+
+	struct tck_bitbang bitbang
+	bitbang.tms = 1;
+	bitbang.tdi = 0;
+	ioctl(jtag_fd, JTAG_IOCBITBANG, &bitbang);
+	tdo = bitbang.tdo;
+
+
+THANKS TO
+---------
+Contributors to Linux-JTAG discussions include (in alphabetical order,
+by last name):
+
+- Ernesto Corona
+- Jiri Pirko
+- Oleksandr Shamray
+- Steven Filary
+- Vadim Pasternak
-- 
2.17.1