From 72548e836b0c4abbb652e791dee9c91203a9a4c6 Mon Sep 17 00:00:00 2001 From: Matt Fleming Date: Fri, 4 Oct 2013 09:36:56 +0100 Subject: x86/efi: Add EFI framebuffer earlyprintk support It's incredibly difficult to diagnose early EFI boot issues without special hardware because earlyprintk=vga doesn't work on EFI systems. Add support for writing to the EFI framebuffer, via earlyprintk=efi, which will actually give users a chance of providing debug output. Cc: H. Peter Anvin Acked-by: Ingo Molnar Cc: Thomas Gleixner Cc: Peter Jones Signed-off-by: Matt Fleming --- Documentation/kernel-parameters.txt | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) (limited to 'Documentation/kernel-parameters.txt') diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index 7f9d4f53882c..7a0f202d482e 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt @@ -792,6 +792,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted. earlyprintk= [X86,SH,BLACKFIN,ARM] earlyprintk=vga + earlyprintk=efi earlyprintk=xen earlyprintk=serial[,ttySn[,baudrate]] earlyprintk=serial[,0x...[,baudrate]] @@ -805,7 +806,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted. Append ",keep" to not disable it when the real console takes over. - Only vga or serial or usb debug port at a time. + Only one of vga, efi, serial, or usb debug port can + be used at a time. Currently only ttyS0 and ttyS1 may be specified by name. Other I/O ports may be explicitly specified @@ -819,8 +821,8 @@ bytes respectively. Such letter suffixes can also be entirely omitted. Interaction with the standard serial driver is not very good. - The VGA output is eventually overwritten by the real - console. + The VGA and EFI output is eventually overwritten by + the real console. The xen output can only be used by Xen PV guests. -- cgit v1.2.3