Re: [PATCH v8 0/5] usb: early: add support for early printk through USB3 debug port

[Ingo Molnar]

* Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> wrote:

> xHCI debug capability (DbC) is an optional but standalone
> functionality provided by an xHCI host controller. With DbC
> hardware initialized, the system will present a debug device
> through the USB3 debug port (normally the first USB3 port).
> The debug device is fully compliant with the USB framework
> and provides the equivalent of a very high performance (USB3)
> full-duplex serial link between the debug host and target.
> The DbC functionality is independent of xHCI host.
> 
> This patch set adds support for early printk functionality
> through a USB3 debug port by 1) initializing and enabling
> the DbC hardware during early boot; 2) registering a boot
> console to the system so that early printk messages can go
> through the USB3 debug port. It also includes some lines
> of changes in usb_debug driver so that it can be bound when
> a USB3 debug device is enumerated.
>
[...]
>
> Lu Baolu (5):
>   x86: add simple udelay calibration
>   usb: early: add driver for xhci debug capability
>   x86: add support for earlyprintk via USB3 debug port
>   usb: serial: add dbc debug device support to usb_debug
>   usb: doc: add document for USB3 debug port usage
> 
>  Documentation/admin-guide/kernel-parameters.txt |    1 +
>  Documentation/usb/usb3-debug-port.rst           |  100 +++
>  arch/x86/Kconfig.debug                          |   23 +
>  arch/x86/kernel/early_printk.c                  |    5 +
>  arch/x86/kernel/setup.c                         |   26 +
>  drivers/usb/Makefile                            |    2 +-
>  drivers/usb/early/Makefile                      |    1 +
>  drivers/usb/early/xhci-dbc.c                    | 1014 +++++++++++++++++++++++
>  drivers/usb/early/xhci-dbc.h                    |  211 +++++
>  drivers/usb/serial/usb_debug.c                  |   28 +-
>  include/linux/usb/xhci-dbgp.h                   |   29 +
>  11 files changed, 1436 insertions(+), 4 deletions(-)
>  create mode 100644 Documentation/usb/usb3-debug-port.rst
>  create mode 100644 drivers/usb/early/xhci-dbc.c
>  create mode 100644 drivers/usb/early/xhci-dbc.h
>  create mode 100644 include/linux/usb/xhci-dbgp.h

Ok, this has now become a high quality series with picture-perfect patches AFAICS. 

Thomas also gave his Acked-by to all the patches.

I've applied them locally to -tip (it appears the USB maintainers are still fine 
with this being carried in tip:x86/debug for a v4.12 merge, right?), and will push 
them out and will propagate them to linux-next as well if they pass testing.

Thanks for the great work!

	Ingo