linux-kernel - Re: [PATCH v5 0/4] usb: early: add support for early printk through USB3 debug port

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Date:   Wed, 18 Jan 2017 14:20:30 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Mathias Nyman <mathias.nyman@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>, tglx@...utronix.de,
        peterz@...radead.org, linux-usb@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 0/4] usb: early: add support for early printk through
 USB3 debug port

Hi Greg,

This patch series has been there for 2 months without
further comments. Will you consider it for usb-next?

Best regards,
Lu Baolu

On 11/15/2016 02:02 PM, Lu Baolu 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. There
> isn't any precondition from xHCI host side for DbC to work.
>
> 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.
>
> This code is designed to be used only for kernel debugging
> when machine crashes very early before the console code is
> initialized. It makes the life of kernel debugging easier
> when people work with a modern machine without any legacy
> serial ports.
>
> ---
> Change log:
> v4->v5:
>   - add raw_spin_lock to make xdbc_bulk_write() reentrant. 
>
> v3->v4:
>   - Rename the document with .dst suffix.
>   - Add the list of hardware that has been succesfuly
>     tested on in the document.
>
> v2->v3:
>   - Removed spinlock usage.
>   - Removed work queue usage.
>   - Refined the user guide document.
>
> v1->v2:
>   - Refactor the duplicate code in xdbc_early_start() and
>     xdbc_handle_external_reset().
>   - Free resources when hardware not used any more.
>   - Refine the user guide document.
>
> Lu Baolu (4):
>   usb: dbc: early driver for xhci debug capability
>   x86: add support for earlyprintk via USB3 debug port
>   usb: serial: usb_debug: add support for dbc debug device
>   usb: doc: add document for USB3 debug port usage
>
>  Documentation/kernel-parameters.txt   |    1 +
>  Documentation/usb/usb3-debug-port.rst |   95 +++
>  arch/x86/Kconfig.debug                |   14 +
>  arch/x86/kernel/early_printk.c        |    5 +
>  arch/x86/kernel/setup.c               |    7 +
>  drivers/usb/Kconfig                   |    3 +
>  drivers/usb/Makefile                  |    2 +-
>  drivers/usb/early/Makefile            |    1 +
>  drivers/usb/early/xhci-dbc.c          | 1068 +++++++++++++++++++++++++++++++++
>  drivers/usb/early/xhci-dbc.h          |  205 +++++++
>  drivers/usb/serial/usb_debug.c        |   28 +-
>  include/linux/usb/xhci-dbgp.h         |   22 +
>  12 files changed, 1447 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
>