Messages in this thread | | | From | Linus Walleij <> | Date | Thu, 24 Aug 2017 23:07:29 +0200 | Subject | Re: [patch v6 0/3] JTAG driver introduction |
| |
On Tue, Aug 22, 2017 at 6:10 PM, Oleksandr Shamray <oleksandrs@mellanox.com> wrote:
> 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.
I guess you mean it should then use GPIO lines for bit-banging?
I was wondering about how some JTAG clients like openOCD does this in some cases.
In my worst nightmare they export GPIO lines using the horrid ABI in /sys/gpio/*
In best case they use the GPIO character device or even libgpiod.
But having a JTAG abstraction inside the kernel that can grab a few lines for JTAG defined in a device tree, ACPI DSDT or similar makes sense too, as it abstracts the hardware so the JTAG client can then just open whatever /dev/jtag0 is on the machine and go ahead without having to bother about what GPIO lines are connected exactly where.
Yours, Linus Walleij
| |