Re: [PATCH 09/12] i386/x86_64: EHCI usb debug port early printk support.
- From: Andi Kleen <ak@xxxxxxx>
- Date: Mon, 30 Apr 2007 19:56:08 +0200
Thanks for writing that code. It should be an interesting alternative
on boxes where firescope doesn't work.
I hope I can eventually merge early firewire support code too.
On Mon, Apr 30, 2007 at 10:32:02AM -0600, Eric W. Biederman wrote:
With legacy free systems serial ports have stopped being an option
to get early boot traces and other debug information out of a machine.
This needs a CONFIG_* at least. And some documentation on how to set it
up on both sides.
This debug device can be used to replace serial ports for
kgdb, kdb, and console support. And gregkh has a simple usb
serial driver for it so user space applications that control
serial ports should work unmodified.
But not merged yet, right? I was hoping it could be done from
user space anyways.
For users the hard part looks like it will be finding cables and
finding which is usb debug port 1 and realizing that there is
flow control so the kernel boot will not happen if someone is not
reading the serial console data.
That's nasty. Any way to work around that?
index 92213d2..dc097aa 100644
--- a/arch/x86_64/kernel/early_printk.c
+++ b/arch/x86_64/kernel/early_printk.c
@@ -3,9 +3,19 @@
#include <linux/init.h>
#include <linux/string.h>
#include <linux/screen_info.h>
+#include <linux/usb/ch9.h>
+#include <linux/pci_regs.h>
+#include <linux/pci_ids.h>
+#include <linux/errno.h>
Can you put it in a separate file please?
Perhaps with a little abstraction in drivers/usb ?
+static void dbgp_breath(void)
+{
+ /* Sleep to give the debug port a chance to breathe */
But you don't?
+static __u32 __init find_dbgp(int ehci_num, unsigned *rbus, unsigned *rslot, unsigned *rfunc)
This should be probably merged into the early quirks loop
early_console = &simnow_console;
keep_early = 1;
+ } else if (!strncmp(buf, "dbgp", 4)) {
usb would seem to be more intuitive
-Andi
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- Re: [PATCH 09/12] i386/x86_64: EHCI usb debug port early printk support.
- References:
- [PATCH 0/12] Early USB debug port and i386 boot cleanups
- From: Eric W. Biederman
- [PATCH 01/12] x86_64: Allow fixmaps to be used with the initial page table.
- From: Eric W. Biederman
- [PATCH 02/12] i386 head.S: Remove unnecessary use of %ebx as the boot cpu flag
- From: Eric W. Biederman
- [PATCH 03/12] i386 head.S: Always run the full set of paging state
- From: Eric W. Biederman
- [PATCH 04/12] i386 voyager: Use modern techniques to setup and teardown low identiy mappings.
- From: Eric W. Biederman
- [PATCH 05/12] i386: During page table initialization always set the leaf page table entries.
- From: Eric W. Biederman
- [PATCH 06/12] i386: Minimum cpu detection cleanups.
- From: Eric W. Biederman
- [PATCH 07/12] i386: Add missing !X86_PAE dependincy to the 2G/2G split.
- From: Eric W. Biederman
- [PATCH 08/12] i386: Convert the boot time page tables to the kernels native format.
- From: Eric W. Biederman
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