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Message-ID: <987ed5f9-38c9-319e-ccd7-509b3a9eae1c@infradead.org>
Date: Thu, 10 May 2018 10:24:47 -0700
From: Randy Dunlap <rdunlap@...radead.org>
To: Oleksandr Shamray <oleksandrs@...lanox.com>,
gregkh@...uxfoundation.org, arnd@...db.de
Cc: linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
devicetree@...r.kernel.org, openbmc@...ts.ozlabs.org,
joel@....id.au, jiri@...nulli.us, tklauser@...tanz.ch,
linux-serial@...r.kernel.org, vadimp@...lanox.com,
system-sw-low-level@...lanox.com, robh+dt@...nel.org,
openocd-devel-owner@...ts.sourceforge.net,
linux-api@...r.kernel.org, davem@...emloft.net, mchehab@...nel.org,
Pavel Machek <pavel@....cz>
Subject: Re: [patch v19 4/4] Documentation: jtag: Add ABI documentation
On 05/10/2018 08:44 AM, Oleksandr Shamray wrote:
> Added document that describe the ABI for JTAG class drivrer
>
> Signed-off-by: Oleksandr Shamray <oleksandrs@...lanox.com>
> Acked-by: Arnd Bergmann <arnd@...db.de>
> ---
> v18-v19
> Pavel Machek <pavel@....cz>
> - Added JTAG doccumentation to Documentation/jtag
>
> v17->v18
> v16->v17
> v15->v16
> v14->v15
> v13->v14
> v12->v13
> v11->v12
> Tobias Klauser <tklauser@...tanz.ch>
> - 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 Kernel Version and Date in jtag-dev documentation;
> v8->v9
> v7->v8
> v6->v7
> Comments pointed by Pavel Machek <pavel@....cz>
> - Added jtag-cdev documentation to Documentation/ABI/testing folder
> ---
> Documentation/ABI/testing/jtag-dev | 27 +++++++++
> Documentation/jtag/overview | 31 ++++++++++
> Documentation/jtag/transactions | 108 ++++++++++++++++++++++++++++++++++++
> 3 files changed, 166 insertions(+), 0 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..e35afc0
> --- /dev/null
> +++ b/Documentation/jtag/overview
> @@ -0,0 +1,31 @@
> +Linux kernel JTAG support
> +=========================
> +
> +The JTAG (Joint Test Action Group) is an industry standard for hardware
just: JTAG
drop the "The"
maybe: for verifying
hardware designs
(although that's not quite what wikipedia says)
> +verifying designs and testing printed circuit boards after manufacture.
> +JTAG provides access to many logic signals of a complex integrated circuit,
> +including the device pins
pins.
Oh. Just drop the 2 lines above since they are repeated below.
> +
> +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 supposed to have two parts - basic core driver and
is designed
> +hardware specific driver.
> +The basic driver introduces general interface which is not dependent of specific
introduces a general interface
> +hardware. It provides communication between user space and hardware specific
and a hardware specific
> +driver.
> +Each JTAG device is represented as char device from (jtag0, jtag1, ...).
as a char device
> +Access to JTAG device is performed through IOCTL call.
Access to a JTAG device is performed through IOCTL calls.
> +
> +Call flow example:
User: open /dev/jtagX
> +User (IOCTL) -> /dev/jtagX -> JTAG core driver -> JTAG hw specific driver
User: close /dev/jtagX
> diff --git a/Documentation/jtag/transactions b/Documentation/jtag/transactions
> new file mode 100644
> index 0000000..91f7f92
> --- /dev/null
> +++ b/Documentation/jtag/transactions
> @@ -0,0 +1,108 @@
> +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 Data Register scan);
Why is SIR for Data Register?
> +- SDR (Scan Data Register, IEEE 1149.1 Instruction Register scan);
Why is SDR for Instruction Register?
> +- RUNTEST (Forces the IEEE 1149.1 bus to a run state for a specified
> +number of clocks.
> +
> +open(), close()
> +-------
> +open() opens JTAG device. Only one open operation per JTAG device
> +can be performed. Twice and more open for one device will return error
Two or more opens for one device will return errors.
> +
> +Open/Close device:
> +- open('/dev/jtag0', O_RDWR);
open("/dev/jtag0", O_RDWR);
> +- close(jtag_fd');
close(jtag_fd);
> +
> +ioctl()
> +-------
> +All access operations to JTAG device performed trougth ioctl interface.
devices are performed through the ioctl interface.
> +It support another requests:
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.
> +
> +JTAG_SIOCFREQ, JTAG_GIOCFREQ
> +------
> +Set/Get JTAG clock speed:
> +
unsigned int frq;
> + ioctl(jtag_fd, JTAG_SIOCFREQ, &frq);
> + ioctl(jtag_fd, JTAG_GIOCFREQ, &frq);
> +
> +JTAG_IOCRUNTEST
> +------
> +Force JTAG state machine to RUN_TEST/IDLE state
> +
> +struct jtag_run_test_idle {
> + __u8 reset;
> + __u8 endstate;
> + __u8 tck;
> +};
> +
> +reset: 0 - run IDLE/PAUSE from current state
> + 1 - go through TEST_LOGIC/RESET state before IDLE/PAUSE
> +end: completion flag
endstate:
> +tck: clock counter
> +
> +Example:
> + struct jtag_run_test_idle runtest;
> +
> + runtest.endstate = JTAG_STATE_IDLE;
> + runtest.reset = 0;
> + runtest.tck = data_p->tck;
> + usleep(25 * 1000);
> + ioctl(jtag_fd, JTAG_IOCRUNTEST, &runtest);
> +
> +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_SIR_XFER/JTAG_SDR_XFER,
> +length: xfer data len in bits
> +tdio : xfer data array
> +endir: xfer end state after transaction finish
endstate:
> + can be: JTAG_STATE_IDLE/JTAG_STATE_PAUSEIR/JTAG_STATE_PAUSEDR
> +
> +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
> + xfer.direction = JTAG_WRITE_XFER;
> +
> + ioctl(jtag_fd, JTAG_IOCXFER, &xfer);
> +
> +JTAG_SIOCMODE
> +------
> +If hw driver can support different running modes you can change it.
> +
> +Example:
> + int mode;
+#define JTAG_SIOCMODE _IOW(__JTAG_IOCTL_MAGIC, 5, unsigned int)
so:
unsigned int mode;
> + mode = JTAG_XFER_HW_MODE;
> + ioctl(jtag_fd, JTAG_SIOCMODE, &mode);
>
--
~Randy
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