Messages in this thread | | | From | Raul Rangel <> | Date | Fri, 14 Jul 2023 11:24:59 -0600 | Subject | Re: [PATCH] init: Don't proxy console= to earlycon |
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On Fri, Jul 14, 2023 at 11:21 AM Raul Rangel <rrangel@chromium.org> wrote: > > On Fri, Jul 14, 2023 at 10:38 AM Petr Mladek <pmladek@suse.com> wrote: > > > > On Mon 2023-07-10 09:30:19, Raul Rangel wrote: > > > 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. > > > > Sigh, I wasn't aware of this when we discussed the console= handling. > > It took a bit of digging to figure out what the actual intention was :) > > > > > > 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. > > > > But this happens only when both "earlycon" and "console=" parameters > > are used together. Do I get it correctly? > > The bug shows up when an SPCR table is present and the `console=` > parameter is set. No need to specify `earlycon` on the command line. > > > > > This combination is ambiguous on its own. Why would anyone add > > "earlycon" parameter and wanted to keep it disabled? > > This is not the case I'm hitting. I'm honestly not sure what the > behavior should be in the `earlycon console=` case? > > > > > > > >>> 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); > > > > >>> } > > > > Huh, this is getting more and more complicated. > > > > You know, it is already bad that: > > > > + "console" enables the default console which might be overridden > > by ACPI SPCR and devicetree > > That's what this patch fixes. You need to specify `earlycon` in order > to get the ACPI SPCR or DT console. > > > > > + "console=" causes that "ttynull" console is preferred, > > it might cause that no console is registered at all > > This patch also makes it so `console=` no longer enables the earlycon. > > > > > + both "earlyconsole" and "earlyconsole=" cause that > > > > consoles is enabled > > > > > > It is already bad that "earlycon" and "console" handle the empty value > > a different way. But this makes it even worse. The behaviour > > would depend on a subtle difference whether "console" or > > "console=" is used. > > This patch makes it so that `console` or `console=` don't enable > earlycon. Earlycon can only be enabled via `earlycon` or `earlycon=`.
Sorry, I misspoke. Earlycon that is configured using the SPCR/DT can only be enabled via `earlycon` or `earlycon=`. You can still enable `earlycon` via `earlycon=uart,mmio32,0xFFFFFFFF` or `console=uart,mmio32,0xFFFFFFFF`.
> > I don't see the `console` (without the =) documented: > https://www.kernel.org/doc/html/v6.1/admin-guide/kernel-parameters.html. > I'm guessing this is an undocumented "feature" that snuck in while the > `earlycon` stuff was being added. > > > > > > > > > > > >> > > > > > > > > > > > > > -- > > > > ~Randy > > Thanks for reviewing, > Raul
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