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

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Date:   Tue, 21 Mar 2017 13:27:36 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Ingo Molnar <mingo@...nel.org>
Cc:     Lu Baolu <baolu.lu@...ux.intel.com>,
        Ingo Molnar <mingo@...hat.com>,
        Mathias Nyman <mathias.nyman@...ux.intel.com>,
        tglx@...utronix.de, peterz@...radead.org,
        linux-usb@...r.kernel.org, x86@...nel.org,
        linux-kernel@...r.kernel.org, Johan Hovold <johan@...nel.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH v8 0/5] usb: early: add support for early printk through
 USB3 debug port

On Tue, Mar 21, 2017 at 12:33:28PM +0100, Ingo Molnar wrote:
> 
> * Lu Baolu <baolu.lu@...ux.intel.com> 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.

Yes, no objection from me.

thanks,

greg k-h