Hi Oleksandr, [My attention was drawn by https://lwn.net/Articles/734440/] [CC linux-spi, which was never included, while linux-serial was] On Thu, Sep 21, 2017 at 11:25 AM, Oleksandr Shamray <oleksandrs@xxxxxxxxxxxx> wrote: > When a need raise up to use JTAG interface for system's devices > programming or CPU debugging, usually the user layer > application implements jtag protocol by bit-bang or using a > proprietary connection to vendor hardware. > This method can be slow and not generic. > > We propose to implement general JTAG interface and infrastructure > to communicate with user layer application. In such way, we can > have the standard JTAG interface core part and separation from > specific HW implementation. > This allow new capability to debug the CPU or program system's > device via BMC without additional devices nor cost. > > This patch purpose is to add JTAG master core infrastructure by > defining new JTAG class and provide generic JTAG interface > to allow hardware specific drivers to connect this interface. > This will enable all JTAG drivers to use the common interface > part and will have separate for hardware implementation. > > The JTAG (Joint Test Action Group) core driver provides minimal generic > JTAG interface, which can be used by hardware specific JTAG master > controllers. By providing common interface for the JTAG controllers, > user space device programing is hardware independent. > > Modern SoC which in use for embedded system' equipped with > internal JTAG master interface. > This interface is used for programming and debugging system's > hardware components, like CPLD, FPGA, CPU, voltage and > industrial controllers. > Firmware for such devices can be upgraded through JTAG interface during > Runtime. The JTAG standard support for multiple devices programming, > is in case their lines are daisy-chained together. > > For example, systems which equipped with host CPU, BMC SoC or/and > number of programmable devices are capable to connect a pin and > select system components dynamically for programming and debugging, > This is using by the BMC which is equipped with internal SoC master > controller. > For example: > > BMC JTAG master --> pin selected to CPLDs chain for programming (filed > upgrade, production) > BMC JTAG master --> pin selected to voltage monitors for programming > (field upgrade, production) > BMC JTAG master --> pin selected to host CPU (on-site debugging > and developers debugging) > > For example, we can have application in user space which using calls > to JTAG driver executes CPLD programming directly from SVF file > > The JTAG standard (IEEE 1149.1) defines the next connector pins: > - TDI (Test Data In); > - TDO (Test Data Out); > - TCK (Test Clock); > - TMS (Test Mode Select); > - TRST (Test Reset) (Optional); > > The SoC equipped with JTAG master controller, performs > device programming on command or vector level. For example > a file in a standard SVF (Serial Vector Format) that contains > boundary scan vectors, can be used by sending each vector > to the JTAG interface and the JTAG controller will execute > the programming. > > Initial version provides the system calls set for: > - SIR (Scan Instruction Register, IEEE 1149.1 Data Register scan); > - SDR (Scan Data Register, IEEE 1149.1 Instruction Register scan); > - RUNTEST (Forces the IEEE 1149.1 bus to a run state for a specified > number of clocks. > > SoC which are not equipped with JTAG master interface, can be built > on top of JTAG core driver infrastructure, by applying bit-banging of > TDI, TDO, TCK and TMS pins within the hardware specific driver. Or by using an SPI master? Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
