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x86/earlyprintk: Add support for earlyprintk via USB3 debug port

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Add support for earlyprintk by writing debug messages to the
USB3 debug port. Users can use this type of early printk by
specifying the kernel parameter of "earlyprintk=xdbc". This
gives users a chance of providing debugging output.

The hardware for USB3 debug port requires DMA memory blocks.
This requires to delay setting up debugging hardware and
registering boot console until the memblocks are filled.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mathias Nyman <mathias.nyman@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: linux-usb@vger.kernel.org
Link: http://lkml.kernel.org/r/1490083293-3792-4-git-send-email-baolu.lu@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Lu Baolu 2017-03-21 16:01:31 +08:00 committed by Ingo Molnar
parent aeb9dd1de9
commit 1b5aeebf3a
3 changed files with 10 additions and 0 deletions
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1
Documentation/admin-guide/kernel-parameters.txt
View File

@ -989,6 +989,7 @@
earlyprintk=ttySn[,baudrate]
earlyprintk=dbgp[debugController#]
earlyprintk=pciserial,bus:device.function[,baudrate]
earlyprintk=xdbc[xhciController#]
earlyprintk is useful when the kernel crashes before
the normal console is initialized. It is not enabled by

5
arch/x86/kernel/early_printk.c
View File

@ -17,6 +17,7 @@
#include <asm/intel-mid.h>
#include <asm/pgtable.h>
#include <linux/usb/ehci_def.h>
#include <linux/usb/xhci-dbgp.h>
#include <linux/efi.h>
#include <asm/efi.h>
#include <asm/pci_x86.h>
@ -381,6 +382,10 @@ static int __init setup_early_printk(char *buf)
if (!strncmp(buf, "efi", 3))
early_console_register(&early_efi_console, keep);
#endif
#ifdef CONFIG_EARLY_PRINTK_USB_XDBC
if (!strncmp(buf, "xdbc", 4))
early_xdbc_parse_parameter(buf + 4);
#endif
buf++;
}

4
arch/x86/kernel/setup.c
View File

@ -70,6 +70,7 @@
#include <linux/tboot.h>
#include <linux/jiffies.h>
#include <linux/usb/xhci-dbgp.h>
#include <video/edid.h>
#include <asm/mtrr.h>
@ -1144,6 +1145,9 @@ void __init setup_arch(char **cmdline_p)
memblock_set_current_limit(ISA_END_ADDRESS);
memblock_x86_fill();
if (!early_xdbc_setup_hardware())
early_xdbc_register_console();
reserve_bios_regions();
if (efi_enabled(EFI_MEMMAP)) {