From 2a11e1479ef07519bfd6b64ee276905ca84cf817 Mon Sep 17 00:00:00 2001 From: Shenghao Yang Date: Sat, 17 Jan 2026 15:28:27 +0800 Subject: x86/acpi: Add acpi=spcr to use SPCR-provided default console MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The SPCR provided console on x86 is only available as a boot console when earlycon is provided on the kernel command line, and will not be present in /proc/consoles. While it's possible to retain the boot console with the keep_bootcon parameter, that leaves the console using the less efficient 8250_early driver. Users wanting to use the firmware suggested console (to avoid maintaining unique serial console parameters for different server models in large fleets) with the conventional driver have to parse the kernel log for the console parameters and reinsert them. [ 0.005091] ACPI: SPCR 0x000000007FFB5000 000059 (v04 ALASKA A M I 01072009 INTL 20250404) [ 0.073387] ACPI: SPCR: console: uart,io,0x3f8,115200 In commit 0231d00082f6 ("ACPI: SPCR: Make SPCR available to x86")¹ the SPCR console was only added as an option for earlycon but not as an ordinary console so users don't see console output changes. So users can opt in to an automatic SPCR console, make ACPI init add it if acpi=spcr is set. ¹https://lore.kernel.org/lkml/20180118150951.28964-1-prarit@redhat.com/ [ bp: Touchups. ] Signed-off-by: Shenghao Yang Signed-off-by: Borislav Petkov (AMD) Link: https://patch.msgid.link/20260117072827.355360-1-me@shenghaoyang.info --- Documentation/admin-guide/kernel-parameters.txt | 2 ++ 1 file changed, 2 insertions(+) (limited to 'Documentation/admin-guide') diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index a8d0afde7f85..4d2f0bf1f8ab 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -125,6 +125,8 @@ Kernel parameters may result in duplicate corrected error reports. nospcr -- disable console in ACPI SPCR table as default _serial_ console on ARM64 + spcr -- enable console in ACPI SPCR table as + default _serial_ console on x86 For ARM64, ONLY "acpi=off", "acpi=on", "acpi=force" or "acpi=nospcr" are available For RISCV64, ONLY "acpi=off", "acpi=on" or "acpi=force" -- cgit v1.2.3