Messages in this thread Patch in this message | | | From | Raul Rangel <> | Date | Mon, 10 Jul 2023 09:30:19 -0600 | Subject | Re: [PATCH] init: Don't proxy console= to earlycon |
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On Sun, Jul 9, 2023 at 8:43 PM Randy Dunlap <rdunlap@infradead.org> wrote: > > > > On 7/9/23 18:15, Mario Limonciello wrote: > > On 7/9/23 18:46, Randy Dunlap wrote: > >> > >> > >> On 7/7/23 18:17, Raul E Rangel wrote: > >>> Right now we are proxying the `console=XXX` command line args to the > >>> param_setup_earlycon. This is done because the following are > >>> equivalent: > >>> > >>> console=uart[8250],mmio,<addr>[,options] > >>> earlycon=uart[8250],mmio,<addr>[,options] > >>> > >>> In addition, when `earlycon=` or just `earlycon` is specified on the > >>> command line, we look at the SPCR table or the DT to extract the device > >>> options. > >>> > >>> When `console=` is specified on the command line, it's intention is to > >>> disable the console. Right now since we are proxying the `console=` > >> > >> How do you figure this (its intention is to disable the console)? > >
https://www.kernel.org/doc/html/v6.1/admin-guide/kernel-parameters.html says the following: console= { null | "" } Use to disable console output, i.e., to have kernel console messages discarded. This must be the only console= parameter used on the kernel command line.
earlycon= [KNL] Output early console device and options.
When used with no options, the early console is determined by stdout-path property in device tree's chosen node or the ACPI SPCR table if supported by the platform.
The reason this bug showed up is that ChromeOS has set `console=` for a very long time: https://chromium.googlesource.com/chromiumos/platform/crosutils/+/main/build_kernel_image.sh#282 I'm not sure on the exact history, but AFAIK, we don't have the ttyX devices.
Coreboot recently added support for the ACPI SPCR table which in combination with the `console=` arg, we are now seeing earlycon enabled when it shouldn't be.
> > I read that as "it's intention is to disable the default console (tty0)". > > Yes, that "default" word should be there IMO. > > Does this patch affect behavior if someone uses > console=tty0 > i.e., the default? >
No, it shouldn't. This change makes it so that the param_setup_earlycon function gets skipped if there is no value. See https://chromium.googlesource.com/chromiumos/third_party/kernel/+/v6.1/drivers/tty/serial/earlycon.c#223
> > > > IE if I add console=ttyS0,115200,n8 to my kernel command line then I don't get the output on tty0 anymore. If I want it on both then I do > > > > console=ttyS0,115200,n8 console=tty0. > > > >> > >>> flag to the earlycon handler, we enable the earlycon_acpi_spcr_enable > >>> variable when an SPCR table is present. This means that we > >>> inadvertently enable the earlycon. > >>> > >>> This change makes it so we only proxy the console= command if it's > >>> value is not empty. This way we can correctly handle both cases. > >>> > >>> Signed-off-by: Raul E Rangel <rrangel@chromium.org> > >>> --- > >>> > >>> init/main.c | 3 +-- > >>> 1 file changed, 1 insertion(+), 2 deletions(-) > >>> > >>> diff --git a/init/main.c b/init/main.c > >>> index aa21add5f7c54..f72bf644910c1 100644 > >>> --- a/init/main.c > >>> +++ b/init/main.c > >>> @@ -738,8 +738,7 @@ static int __init do_early_param(char *param, char *val, > >>> for (p = __setup_start; p < __setup_end; p++) { > >>> if ((p->early && parameq(param, p->str)) || > >>> (strcmp(param, "console") == 0 && > >>> - strcmp(p->str, "earlycon") == 0) > >>> - ) { > >>> + strcmp(p->str, "earlycon") == 0 && val && val[0])) { > >>> if (p->setup_func(val) != 0) > >>> pr_warn("Malformed early option '%s'\n", param); > >>> } > >> > > > > -- > ~Randy
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