jtag: Add an option to ignore the bypass bit

Some CPU wrongly indicate the bypas bit in the codeid.
It's the case of the NanoXplore NG-ULTRA chip that export a
configurable (and potentially invalid) ID for one of
its component.
Add an option to ignore it.

Signed-off-by: Adrien Grassein <adrien.grassein@gmail.com>
Change-Id: Ic59743f23bfc4d4e23da0e8535fec8ca9e87ff1a
Reviewed-on: https://review.openocd.org/c/openocd/+/6802
Tested-by: jenkins
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
Reviewed-by: Oleksij Rempel <linux@rempel-privat.de>

1 files changed, 4 insertions, 0 deletions

diff --git a/doc/openocd.texi b/doc/openocd.texi
index cee54eb..ed92eb4 100644
--- a/doc/openocd.texi
+++ b/doc/openocd.texi
@@ -4153,6 +4153,10 @@ option. When vendors put out multiple versions of a chip, or use the same
 JTAG-level ID for several largely-compatible chips, it may be more practical
 to ignore the version field than to update config files to handle all of
 the various chip IDs. The version field is defined as bit 28-31 of the IDCODE.
+@item @code{-ignore-bypass}
+@*Specify this to ignore the 'bypass' bit of the idcode. Some vendor put
+an invalid idcode regarding this bit. Specify this to ignore this bit and
+to not consider this tap in bypass mode.
 @item @code{-ircapture} @var{NUMBER}
 @*The bit pattern loaded by the TAP into the JTAG shift register
 on entry to the @sc{ircapture} state, such as 0x01.