> -----Original Message----- > From: geert.uytterhoeven@xxxxxxxxx [mailto:geert.uytterhoeven@xxxxxxxxx] > On Behalf Of Geert Uytterhoeven > Sent: Thursday, September 28, 2017 12:02 PM > To: Oleksandr Shamray <oleksandrs@xxxxxxxxxxxx> > Cc: Greg KH <gregkh@xxxxxxxxxxxxxxxxxxx>; Arnd Bergmann > <arnd@xxxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; linux-arm- > kernel@xxxxxxxxxxxxxxxxxxx; devicetree@xxxxxxxxxxxxxxx; > openbmc@xxxxxxxxxxxxxxxx; Joel Stanley <joel@xxxxxxxxx>; Jiri Pirko > <jiri@xxxxxxxxxxx>; Tobias Klauser <tklauser@xxxxxxxxxx>; linux- > serial@xxxxxxxxxxxxxxx; mec@xxxxxxxxx; Vadim Pasternak > <vadimp@xxxxxxxxxxxx>; system-sw-low-level <system-sw-low- > level@xxxxxxxxxxxx>; Rob Herring <robh+dt@xxxxxxxxxx>; openocd-devel- > owner@xxxxxxxxxxxxxxxxxxxxx; linux-api@xxxxxxxxxxxxxxx; David S. Miller > <davem@xxxxxxxxxxxxx>; Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>; > linux-spi <linux-spi@xxxxxxxxxxxxxxx>; Mark Brown <broonie@xxxxxxxxxx> > Subject: Re: [patch v9 0/4] JTAG driver introduction > > Hi Oleksandr, > > On Thu, Sep 28, 2017 at 10:53 AM, Oleksandr Shamray > <oleksandrs@xxxxxxxxxxxx> wrote: > >> [My attention was drawn by > >> https://emea01.safelinks.protection.outlook.com/?url=https%3A%2F%2Flw > >> n.net > >> > %2FArticles%2F734440%2F&data=02%7C01%7Coleksandrs%40mellanox.com%7 > >> > C97b8ba88686a42daaace08d5064b92eb%7Ca652971c7d2e4d9ba6a4d149256f > >> > 461b%7C0%7C0%7C636421844026854216&sdata=TeHD4a3%2FBN6a5XG3Jizf5 > >> pmsyJHJjzkEzkpnqsXC6S0%3D&reserved=0] > >> [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. > >> > > > > > > > [..] > > > >> > > >> > 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? > >> > > > > I think it depends on how flexible the SPI interface is. If you can > > set it to transfer from 1 to n bits at a time, and you control the TMS > > line in software, you should be able to use it. If the SPI interface > > can only transfer a multiple of 8 bits at a time, then in general it would not be > suitable for JTAG. > > Sure, that depends on the actual SPI master interface. > But I guess you can write a generic JTAG-over-SPI driver, and use a tms-gpios > property in DT to specify how to control TMS. > Yes, this is a good idea for SoC which are not equipped with JTAG hardware. > Gr{oetje,eeting}s, > > Geert > > -- > Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux- > m68k.org > > 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 ��.n��������+%������w��{.n�����{����* jg��� �����ݢj����G���� ���j:+v���w�m������w�������h�����٥
