diff options
| author | Douglas Anderson | 2020-05-07 13:08:47 -0700 |
|---|---|---|
| committer | Daniel Thompson | 2020-06-02 15:15:45 +0100 |
| commit | f71fc3bc7b3279cb7d0ab78c1fcc78825779bb65 (patch) | |
| tree | c01a6cc8543c611e19dce93cdcc1d3a73a332f0f /Documentation/admin-guide | |
| parent | b1350132fef7e1f0ddfd5a985d516a6ed7a329fc (diff) | |
Documentation: kgdboc: Document new kgdboc_earlycon parameter
The recent patch ("kgdboc: Add kgdboc_earlycon to support early kgdb
using boot consoles") adds a new kernel command line parameter.
Document it.
Note that the patch adding the feature does some comparing/contrasting
of "kgdboc_earlycon" vs. the existing "ekgdboc". See that patch for
more details, but briefly "ekgdboc" can be used _instead_ of "kgdboc"
and just makes "kgdboc" do its normal initialization early (only works
if your tty driver is already ready). The new "kgdboc_earlycon" works
in combination with "kgdboc" and is backed by boot consoles.
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Daniel Thompson <daniel.thompson@linaro.org>
Link: https://lore.kernel.org/r/20200507130644.v4.9.I7d5eb42c6180c831d47aef1af44d0b8be3fac559@changeid
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
Diffstat (limited to 'Documentation/admin-guide')
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 7bc83f3d9bdf..2cbde9ea476d 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1190,6 +1190,11 @@ This is designed to be used in conjunction with the boot argument: earlyprintk=vga + This parameter works in place of the kgdboc parameter + but can only be used if the backing tty is available + very early in the boot process. For early debugging + via a serial port see kgdboc_earlycon instead. + edd= [EDD] Format: {"off" | "on" | "skip[mbr]"} @@ -2105,6 +2110,21 @@ kms, kbd format: kms,kbd kms, kbd and serial format: kms,kbd,<ser_dev>[,baud] + kgdboc_earlycon= [KGDB,HW] + If the boot console provides the ability to read + characters and can work in polling mode, you can use + this parameter to tell kgdb to use it as a backend + until the normal console is registered. Intended to + be used together with the kgdboc parameter which + specifies the normal console to transition to. + + The name of the early console should be specified + as the value of this parameter. Note that the name of + the early console might be different than the tty + name passed to kgdboc. It's OK to leave the value + blank and the first boot console that implements + read() will be picked. + kgdbwait [KGDB] Stop kernel execution and enter the kernel debugger at the earliest opportunity. |