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authorLu Baolu <baolu.lu@linux.intel.com>2017-03-21 16:01:31 +0800
committerIngo Molnar <mingo@kernel.org>2017-03-21 12:30:16 +0100
commit1b5aeebf3a92273b4d85aeff37a16037bc3c3abf (patch)
tree5e53cbb34ebef264bceb394985b2ad0b6a60e52f /Documentation/admin-guide
parentaeb9dd1de98c1a5f2007ea5d2a154c1244caf8a0 (diff)
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>
Diffstat (limited to 'Documentation/admin-guide')
-rw-r--r--Documentation/admin-guide/kernel-parameters.txt1
1 files changed, 1 insertions, 0 deletions
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 2ba45caabada..ea1293d60f17 100644
--- 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