Added document that describe the ABI for JTAG class drivrer Signed-off-by: Oleksandr Shamray <oleksandrs@xxxxxxxxxxxx> Acked-by: Arnd Bergmann <arnd@xxxxxxxx> --- 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/jtag/overview | 27 +++++++++ Documentation/jtag/transactions | 109 ++++++++++++++++++++++++++++++++++++ MAINTAINERS | 1 + 4 files changed, 160 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/ABI/testing/jtag-dev b/Documentation/ABI/testing/jtag-dev new file mode 100644 index 0000000..423baab --- /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/jtag/overview b/Documentation/jtag/overview new file mode 100644 index 0000000..3c39052 --- /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 +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..e86fb73 --- /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 performed through ioctl interface. +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 jtag_fd; + 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: + JTAG_NO_RESET - run IDLE/PAUSE from current state + JTAG_FORCE_RESET - go through TEST_LOGIC/RESET state before IDLE/PAUSE +endstate: completion flag +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 length in bits +tdio : xfer data array +endstate: xfer end state after transaction finish + 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 hardware driver can support different running modes you can change it. + +Example: + unsigned int mode; + mode = JTAG_XFER_HW_MODE; + ioctl(jtag_fd, JTAG_SIOCMODE, &mode); diff --git a/MAINTAINERS b/MAINTAINERS index 169de71..0ae2cf8 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -7698,6 +7698,7 @@ F: include/linux/jtag.h F: include/uapi/linux/jtag.h F: drivers/jtag/ F: Documentation/devicetree/bindings/jtag/ +F: Documentation/ABI/testing/jtag-dev K10TEMP HARDWARE MONITORING DRIVER M: Clemens Ladisch <clemens@xxxxxxxxxx> -- 1.7.1 -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html