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

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>

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 2ba45caabada3e88339e88ebdfaaedbb322085c8..ea1293d60f1720508e026cac1a7f5ad78225705a 100644 (file)
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -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

diff --git a/arch/x86/kernel/early_printk.c b/arch/x86/kernel/early_printk.c
index 8a121991e5ba9f742ef6f9b04072bbd06be31ddb..0f0840304452c5e2357621d674daf3d478ae77dc 100644 (file)
--- a/arch/x86/kernel/early_printk.c
+++ b/arch/x86/kernel/early_printk.c
@@ -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++;
        }

diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index e70204e13e48c24158582ccd2781603b0af28538..2600b1d0043b22b218339c24f7779f037b13edb0 100644 (file)
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -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)) {